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Arc Flash Safety Handbook


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Arc Flash Safety Handbook — Volume 1

Table of Contents

High Voltage Safe Work Practices ...................................................................................................... 1Paul Hartman

Electrical Hazard Analysis Changing Standards and Changing Attitudes ........................................... 5Ray Harold

Approach Boundaries ........................................................................................................................ 7John Cadick, P.E.

NFPA 70E 2000 Update ...................................................................................................................... 9John Cadick, P.E.

Protective Devices Maintenance as it Applies to the Arc/Flash Hazard ............................................ 16Dennis K. Neitzel, C.P.E.

Electric Arc Flash Protective Clothing .............................................................................................. 19Paul Hartman

Corrective Measures to Arc Flash Problems — Is It that Simple? .................................................... 22Ron Widup

Electrical Safety — Myths and Rumors ............................................................................................ 26David K. Kreger

Arc Flash Concerns .......................................................................................................................... 29Conrad St. Pierre

Six Steps to Arc Flash Nirvana ......................................................................................................... 35Jim White

Arc Flash Hazards to Be Studied ....................................................................................................... 41Ron Widup and Jim White

Electrical Hazards Analysis .............................................................................................................. 42Dennis K. Neitzel, C.P.E

Electrical PPE Trends ....................................................................................................................... 47Bill Rieth

Proper PPE — A Journey with No End: One Company’s Experiences ............................................... 49Tony Demaria

Arc Flash Safety Handbook — Volume 1

Table of ContentsEmpowering Safety — Part I ............................................................................................................ 51Charlie Simpson

Do I Have to Comply with NFPA 70E? ............................................................................................. 54Lynn Hamrick

Empowering Safety — Part 2 ........................................................................................................... 58Charlie Simpson

Arc Flash Safety Handbook — Volume 1 1

Paul HartmanElectro-Test, Inc.

PowerTest 2000(NETA Annual Technical Conference)

High Voltage Safe Work Practices

The majority of information used to assemble this paper came from two sources, NFPA 70E (Standards for Electri-cal Safety Requirements for Employee Workplaces) and the OSHA Safety Regulations.

For all practical purposes and discussions objects that are not insulated for the voltage being worked on must be considered conductive.

Job AnalysisPrior to any work being performed employees must

determine whether equipment in the area where work is to be performed will be energized or de-energized.

Once the status of the electrical equipment is identified proper working clearances must be maintained.

Working Clearances Below 600 VoltsSufficient access and working space shall be provided

and maintained around electrical equipment to permit safe operation and maintenance of such equipment.

NFPA 70E states that a minimum of three (3) feet is required in front of equipment rated 0-150 volts to ground. This is to ensure that any access to energized equipment requiring examination, adjustment servicing, or maintenance will provide the worker with adequate work space.

For voltages between 151-600 volts to ground, a three (3) foot clearance is still required between exposed live parts and other surfaces. If the other surfaces are grounded, then the distance must be increased to three and a half (3-1/2) feet. If there are exposed live parts on either side of the workspace, then a distance of four (4) feet is required.

Working Clearances Above 600 VoltsFor voltages greater than 600 volts to ground the mini-

mum clearance depth in front of switchgear varies from 3 feet to 12 feet depending on the voltage and proximity to other equipment. The details for determining the proper distances are outline in section 1 of NFPA 70E.

An important aspect of working safely around electrical equipment is to follow the rules associated with working clearances. These working clearances assist in setting up an environment that will help prevent personnel contact with energized circuits and to minimize hazards in the event of an arc/blast.

Flash Protection DistancesAccording to NFPA, 70E flash hazard analysis shall be

done before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrically safe work condition.

In certain instances, the flash protection boundary (dis-tance at which curable burns will occur during a blast) might be a greater distance than the limited approach bound-ary (distance for preventing electrical shock). The greater distance shall be utilized to trigger the need for personal protective equipment.

Figure 1 identifies the flash protection boundary distance for exposed electrical components.

FLASH PROTECTION BOUNDARYPhase to Phase Voltage Distance From Equipment

300 V and less 3 ft 0 inOver 300 V, not over 750 V 3 ft 0 inOver 750 V, not over 2 kV 4 ft 0 inOver 2 kV, not over 15 kV 16 ft 0 inOver 15 kV, not over 36 kV 19 ft 0 inOver 36 kV, not over 800 kV ** For values above 36 kV, calculate the distance by using the formula in figure 2

Figure 1 — Flash protection distances

2 Arc Flash Safety Handbook — Volume 1

Figure 2 — Formula for calculating flash distances

Safe Switching PracticesA high percentage of accidents occur during switch-

ing operations. The following is a suggested switching sequence:• Secureauthorizationbeforeperforminganyswitching,

preferably in writing or as a part of a Standard Operat-ing Plan (SOP).

• Reviewone-linediagramtoidentifyequipmentaffectedby the switching operation.

• Allpersonnelaffectedbytheswitchingoperationshouldbe notified.

• Once theworker isprepared tooperate the switch, itshould be operated as if it may fail. This implies some precautions to be taken:

• Personal protective equipment should be worn. Hardhat, eye glasses or face shield, proper gloves, and long-sleeved protective (cotton or nomex) coveralls are rec-ommended as a minimum. Blast suites are required on high-energy circuits.

• Identify the immediate blast zone. If the switch fails,where will the blast go? If you cannot operate the de-viceremotely,standofftothesidethatoffersthemostprotection from an anticipated blast.

• Haveabackuppersonwhocanrenderassistanceifnec-essary, but make sure they stay out of the immediate blast zone.

• Keepallothersoutoftheswitchingarea.• Makesurepanelcoversanddoorsaresecure.• Before re-energization, verify that all locks and tags

have been removed and the circuit has been visually in-spected and tested safe for re-energization.

Limited Approach BoundaryThe NFPA 70E guidelines for approach distance for

unqualified personnel to exposed energized conductors are shown in figures 3 and 4.

When workers without electrical training are working on the ground or elevated position near overhead lines, the loca-tion shall be such that the person and the longest conductive object that a person might contact cannot come close to any unguarded, energized overhead line that has not been placed into an electrically safe work condition (figure 3).

CURABLE BURNS BOUNDARYDISTANCEFROMELECTRICALEQUIPMENT

Dc=(2.65xMVAbfxt)1/2 orDc=(53xMVAxt)1/2

Where: Dc = Distance of a person from an arc source for a just curable burn, in feet.MVAbf=boltedafultMVAatpointinvolved.MVA=MVAratingoftransformer.Fortransformers withMVAratingbelow0.75MVA,multiply thetransformerMVAratingby1.25. t = time of arc exposure in seconds.

LIMITED APPROACH BOUNDARYEXPOSEDFIXEDCONDUCTOR

Phase to Phase Voltage Distance, Energized Part to Employee

300 V and less 3 ft 6 inOver 300 V, not over 750 V 3 ft 6 inOver 750 V, not over 2 kV 4 ft 0 inOver 2 kV, not over 15 kV 5 ft 0 inOver 15 kV, not over 36 kV 6 ft 0 inOver 36 kV, not over 121 kV 8 ft 0 inOver 138 kV, not over 145 kV 10 ft 0 inOver 161 kV, not over 169 kV 11 ft 8 inOver 230 kV, not over 242 kV 13 ft 0 inOver 345 kV, not over 362 kV 15 ft 4 inOver 500 kV, not over 550 kV 19 ft 0 inOver 765 kV, not over 800 kV 23 ft 9 in

LIMITED APPROACH BOUNDARYEXPOSEDMOVABLECONDUCTOR


300 V and less 10 ft 0 inOver 300 V, not over 72.5 kV 10 ft 0 inOver 72.5 kV, not over 121 kV 10 ft 8 inOver 138 kV, not over 145 kV 11 ft 0 inOver 161 kV, not over 169 kV 11 ft 8 inOver 230 kV, not over 242 kV 13 ft 0 inOver 345 kV, not over 362 kV 15 ft 4 inOver 500 kV, not over 550 kV 19 ft 0 inOver 765 kV, not over 800 kV 23 ft 9 in

Figure 3 — Unqualified personnel minimum approach distance to a movable conductor

When an unqualified worker is working near stationary exposed conductors the location shall be such that they or the longest conductive object does not get within the limited approach boundary (figure 4).

Figure 4 — Unqualified personnel minimum approach distance to a stationary conductor


OSHA — Ten Foot RuleOSHA specifies a minimum clearance from energized 50

kV power lines of 10 feet fro all unqualified workers. This is known as the “10-foot rule.”

For voltage levels above 50 kV an additional four inches for every 10 kV above 50 kV shall be added to the 10’ clear-ance requirement.

A visual representation of the “Ten-Foot Rule” is shown in figure 5.

Figure 5 — Illustration of the ten-foot rule as it applies to substa-tions and overheard lines

Vehicular and Mechanical EquipmentWhere is could reasonably be anticipated that parts of any

vehicle or mechanical equipment structure will be elevated near energized overhead lines, they shall be operated so that the limited approach boundary distance of figure 3 is maintained.

There are exceptions to this rule for when a vehicle is in transit, or the conductors are insulated, or the equipment is designed to be insulated against the voltage being worked on.

The reduced clearances for specific applications, outlined in Section 2 of NFPAA 70E, should be reviewed prior to performing work.

Mobile Equipment in TransitExcept where electrical distribution and transmission

lines have been de-energized and visibly grounded at the

point of work or where insulating barriers rated for the expected voltage have been erected to prevent physical contact with lines or other exposed electrical parts, mobile equipment in transit, with no load attached and boom lowered, shall observe the following minimum dimensional clearances:

(1) 4 feet for voltages less than 50 kV.(2) 10 feet for voltages over 50 kV, up to and includ-

ing 345 kV.(3) 16 feet for voltages up to and including 750 kV.(4) Where it is difficult for the operator to maintain

the desired clearance by visual means, a person shall be designated to observe clearance as an aid to the operator.

Qualified Person Approach DistancesNo qualified persons shall approach or take any conduc-

tive object, without a suitable insulated handle, closer to exposed energized conductors or circuit parts than the dis-tances listed in figure 6, “Restricted Approach Boundary.”

Figure 6 — Restricted approach distances

No qualified person shall approach or take any conductive object without a suitable insulated handle closer to exposed energized electrical conductors or circuit parts than the restricted approach boundary unless:

(a) The qualified person is insulated or guarded from the energized conductors or circuits parts and no unguard-ed part of the person’s body enters into the prohibited space identified in figure 7.

1 ArcFlashSafetyHandbook—Volume1

RESTRICTED APPROACH BOUNDARYSTANDARD INADVERTENT MOVEMENT BOUNDARY


300 V and less Avoid ContactOver 300 V, not over 750 V 1 ft 0 inOver 750 V, not over 2 kV 2 ft 0 inOver 2 kV, not over 15 kV 2 ft 2 inOver 15 kV, not over 36 kV 2 ft 7 inOver 36 kV, not over 48.3 kV 2 ft 10 inOver 48.3 kV, not over 72.5 kV 3 ft 3 inOver 72.5 kV, not over 121 kV 3 ft 5 inOver 138 kV, not over 145 kV 3 ft 7 inOver 161 kV, not over 169 kV 4 ft 0 inOver 230 kV, not over 242 kV 5 ft 3 inOver 345 kV, not over 362 kV 8 ft 6 inOver 500 kV, not over 550 kV 11 ft 3 inOver 765 kV, not over 800 kV 14 ft 11 in


(b) The energized conductor or circuit part is insulated or guarded from all conductive objects at a potential dif-ferent from that of the energized part.

(c) The qualified person is isolated, insulated, or guarded from all conductive objects at a potential differentform that of the energized part. Any variation from the requirements of (a), (b), or (c) above requires ad-ditional hazard/risk analysis.

PROHIBITED APPROACH BOUNDARYREDUCEDINDAVERTENTMOVEMENTBOUNDARY


300 V and less Avoid ContactOver 300 V, not over 750 V 0 ft 1 inOver 750 V, not over 2 kV 0 ft 3 inOver 2 kV, not over 15 kV 0 ft 7 inOver 15 kV, not over 36 kV 0 ft 10 inOver 36 kV, not over 48.3 kV 1 ft 5 inOver 48.3 kV, not over 72.5 kV 2 ft 1 inOver 72.5 kV, not over 121 kV 2 ft 8 inOver 138 kV, not over 145 kV 3 ft 1 inOver 161 kV, not over 169 kV 3 ft 6 inOver 230 kV, not over 242 kV 4 ft 9 inOver 345 kV, not over 362 kV 8 ft 0 inOver 500 kV, not over 550 kV 10 ft 9 inOver 765 kV, not over 800 kV 14 ft 5 in

Figure 7 — Prohibited approach distances

Access RequirementsThe entrances to all buildings, rooms, or enclosures con-

taining exposed live parts or exposed conductor operating at over 600 volts, nominal, shall be kept locked or shall be under the observation of a qualified person at all times.

Installations Accessible to Unqualified Persons

Electrical installations that are open to unqualified persons shall be made with metal-enclosed equipment or shall be enclosed in a vault or in an area, access to which is controlled by a lock.

Metalenclosedswitchgear,unitsubstations,transform-ers, pull boxes, connection boxes, and other similar associ-ated equipment shall be marked with appropriate caution signs. Ventilation or similar openings in metal-enclosed equipment shall be designed so that foreign objects in-serted through these openings will be deflected away from energized parts.

PaulHartman is aNETACertifiedSeniorTechnician/Level IVworkingasafieldengineerandinstructorfortheETILearningCenter,adivisionofElectro-Test,Inc.,aNETAFullMember.Heisaregularcontributor to NETA World and to the Annual Technical Conference.


Electrical Hazard Analysis Changing Standards and Changing Attitudes

NETA World, Summer 2000 Issue

by Ray Harold, Senior Training SpecialistAVO Training Institute

The petrochemical industry and many government insti-tutions have performed research on the subject of electrical hazards for over twenty years. For the most part, however, the electrical industry, at least at the user level, has largely ignored the subject — essentially reacting to catastrophic accidents rather than proactively trying to predict and pre-vent them. Recent changes in consensus standards, along with a better general understanding of the seriousness of electrical hazards, has resulted in a renewal of interest in the subject. This article provides an overview of the three principle types of electrical hazard analysis along with a discussion of the relevant standards and regulations per-taining to the subject.

Shock Hazard AnalysisEach year several hundred workers are killed as a result of

inadvertent contact with energized conductors. Surprisingly, over half of those killed are not traditionally in electrical fields (i.e., linemen, electricians, technicians). Recent in-vestigations into the causes of these fatalities point to three principle causal factors: Failure to properly or completely de-energize systems

prior to maintenance or repair work. Intentionally working on energized equipment. Improper or inadequate grounding of electrical system

components.

These factors form the basis for analysis of the elec-trical shock hazard. To appropriately assess the electrical shock hazard associated with any type of maintenance or repair work, it is necessary to evaluate procedures or work practices that will be involved. These prac-tices should be evaluated against both regulatory re-quirements and recognized good practice within the industry. These principles are summarized below.

Regulatory Requirements All equipment must be placed in a de-energized state

priortoanymaintenanceorrepairwork.(Limitedex-ceptions exist.)

The de-energized state must be verified prior to any work.

The de-energized state must be maintained through the consistent use of locks and tags.

When energized work is performed, it must be per-formed in accordance with written procedures.

Industry-Recognized Good Practice Plan every job. Anticipate unexpected results. Useproceduresastools. Identify the hazards. Assess employees’ abilities.

In addition to the assessment of work practices and procedures against these principles, shock hazard analysis must include an assessment of the physical condition of the electrical system. Although the continuity and low resistance of the equipment grounding system is a major concern, it is not the only one. Of equal importance is the assurance that covers and guards are in place, access to exposed conductors is limited to electrically qualified personnel, and overcurrent protective devices are operable and of appropriate rating. Even the safest procedures performed on poorly constructed or maintained facilities represent a risk to employees.


Flash Hazard AnalysisAn estimated 75 to 80 percent of all serious electrical

injures are related to electrical arcs created during short circuits and switching procedures. In recognition of this fact, standards organizations such as the National Fire Protection Association (NFPA) have attempted to provide the industry with better techniques to evaluate both the magnitude of the electrical arc hazard and appropriate protective clothing. An electrical arc is basically an electrical current passing through ionized air. This current flow releases a tremendous amount of energy as both radiated light and convected heat. The amount of liberated energy is obviously dependent upon the system configuration, but the principle factors used in the determination of the hazard to personnel are as follows: Available short-circuit current at the arc location Duration of the electrical arc Distance from the arc to personnel Environmental conditions and surroundings at the arc

location.

To accurately assess the arc hazard and make appropriate decisions regarding protective clothing, it is necessary to fully understand the operation of the system under fault conditions. This requires both a short-circuit study, in all likelihood down to the panelboard level, and a coordination study. With this information available, the magnitude of the arc hazard at each work location can be assessed using several techniques. These techniques include: Tables and equations (published by various sources, in-

cluding NFPA 70E) Freeware – authored by Duke Power and available on

the internet Commercial software – available from Ontario Hydro

Technologies

Each of these techniques requires an understanding of anticipated fault conditions and the limitation of the calculation method, both of which are beyond the scope of this article.

The results of the arc hazard assessment are most useful when expressed in terms of the incident energy received by exposed personnel. Incident energy is commonly expressed in terms of calories per cm2. Arc protective clothing is rated in terms of its average thermal performance value (ATPV), also expressed in terms of cal/cm2. Thus, at least in theory, personnel can be protected by simply matching the protective clothing rating to the magnitude of the arc at a given location. While this technique sounds relatively straightforward, there is one problem. In some system configurations, particularly high-voltage utility type applica-tions, no available clothing will provide sufficient protection for employees. In these cases, work practices used by em-ployees, including clothing, tools, line clearance procedures,

and other factors, must be carefully scrutinized to insure the risk to employees is minimized. As with the electrical shock hazard,theeasiestandmosteffectivewaytomitigatethearc hazard is to completely de-energize the system.

Blast Hazard AnalysisAn electrical blast or explosion, as it is often termed, is

theresultoftheheatingeffectsofanelectricalarc.Thisphe-nomenon occurs in nature as the thunder that accompanies lightning, a natural form of an electrical arc.

During an electrical arc, both the conducting material and the surrounding air are heated to extremely high tem-peratures. The resulting expansion of the air and vaporized conductive material creates a concussive wave surrounding the arc. The pressures in this wave may reach several hun-dred lbf/ft2, destroying equipment enclosures and throwing debris great distances.

The blast hazard is analyzed in a manner similar to the arc hazard. The pressure created during an electrical explosion is directly proportional to the available short circuit at the arc location. With a current short-circuit study available, the anticipated blast pressure can be estimated from tables or charts.

Unfortunately, little canbedone tomitigate theblasthazard, at least in terms of personal protective clothing or equipment. Blast pressure calculations can be used to deter-mine whether enclosures will withstand an internal fault, if sufficient manufacturer’s data is available. Again, it may be more important to merely recognize the magnitude of the hazard so appropriate safety practices, such as correct body positioning, can be incorporated into work procedures.

ConclusionsRegulatory agencies and standards organizations have

long recognized the need to analyze the hazards of electrical workandplanaccordinglytomitigatethehazards.Unfor-tunately, many in the electrical industry have chosen to “take their chances” largely because nothing bad has happened yet. As more information becomes available on the economic and human costs of electrical accidents, it is hoped more people in the industry will recognize the need for systematic hazard analysis and an electrical safe work program that emphasizes hazard identification and abatement.

Ray C. Harold, Senior Training Specialist for AVO International Training Institute, Dallas, Texas, earned his BS Degree in Electrical EngineeringatKansasStateUniversity,Manhattan,KS,graduatingCumLaudeGraduate,HonorsProgramin1983.HeisatechnicalinstructoratAVO with responsibilities in curriculum development, course presenta-tions, and electrical safety inspections. He has fifteen years’ experience in commercial, industrial, and research-and-development environments as well as eight years of supervisory experience.


Approach Boundaries

NETA World, Winter 2000-2001 Issue

by John Cadick, P.E.Cadick Corporation

Figure 1 — NFPA 70E Approach Boundaries

AsshowninFigure1,NFPA70Edefinesfourdifferentapproach boundaries for personnel safety. Note that the flash boundary is shown as a dashed line because, as we will describe later, its actual location varies as a function of available short circuit duty.

Limited BoundaryThe limited boundary is for unqualified personnel. No

unqualified person may approach any exposed energized conductor any closer than the limited approach boundary. The limited approach boundary is determined by referring to Table 2-1.3.4 in NFPA 70E - Page 51. (2000 Edition.)

Note that in the 2000 Edition NFPA has added the concept of movable or fixed conductors. In 2000 edition unqualified workers may approach nonmoving conductors (fixed buswork for example) more closely than those which may move (overhead lines for example).

Restricted BoundaryGenerally,qualifiedpersonsarenotallowedtoapproach

exposed, energized conductors any closer than the restricted approach boundary unless they are wearing appropriate personal protective equipment (PPE) and they have a writ-ten, approved plan for the work they are to perform. They must break the restricted boundary only to the extent that is absolutely necessary to perform their work. The restricted boundary is determined using Table 2-1.3.4 in NFPA 70E - Page 51. (2000 Edition)

Prohibited BoundaryCrossing the prohibited approach boundary (qualified

personnel only) is considered the same as actually contacting the exposed energized part. In addition to the requirements for restricted boundary approach, personnel must perform a risk assessment before the prohibited boundary is crossed.

The prohibited approach boundary is determined by re-ferring to Table 2-1.3.4 on Page 51 of NFPA 70E. (2000 Edition).

Flash Protection BoundaryThe radiant energy released by an electric arc is capable of

maiming or killing a human being at distances of up to ten or even twenty feet. In addition to radiant heat, the molten material and objects ejected by the electrical blast can also be lethal. The flash protection boundary is the closest ap-proach allowed by qualified or unqualified persons without the use of arc protection PPE. For systems of under 600 volts ac) 70E sets up two possible ways to calculate the flash boundary.

1. For locations with a total fault exposure of less than 5000 ampere-seconds (fault current in amperes multi-plied by clearing time in seconds), a flash boundary of four feet may be used.


2. Above 5000 ampere-seconds, or under engineering su-pervision for all levels, the following formulas may be used:

Dc=√2.65xMVAbf x t (1)

– or –

Dc=√53xMVAxt(2)

Where:

Dc = The flash boundary radiusMVAbf=TheboltedfaultMVAatthepoint of exposureMVA= ThemaximumfaultMVAfromthe transformer feeding the circuitT = The time of exposure (based on protective device operation)

Equation 1 provides generally smaller distances.

For voltage levels in excess of 600 volts, other formulas may be used. The flash boundary is defined as that distance at which the worker is exposed to 1.2 cal/cm2 for exposures of more than 0.1 seconds or 1.5 cal/cm2 for exposures of more than 0.1 seconds.

In Summary for Flash Boundary• Whenanenergizedconductorisexposed,absolutelyno

one may approach closer than the flash boundary with-out wearing appropriate arc protection.

• TheapplicationofEquation1willprovidethesmallerflash boundaries.

• Equation1maynotbeappliedwithoutanaccurate,up-to-date short circuit analysis at the point of exposure.

• If the flash boundary is smaller than the limited ap-proach boundary, the limited approach boundary is the closest that unqualified persons may approach.

A registered professional engineer and the founder and president of the Cadick Corporation, John Cadick has specialized for over three decades in electrical engineering, training, and management. His consult-ingfirm,basedinGarland,Texas,specializesinelectricalengineeringand training and works extensively in the areas of power system design and engineering studies, condition-based maintenance programs, and electrical safety. Prior to creating the Cadick Corporation and its prede-cessor Cadick Professional Services, he held a number of technical and managerial positions with electric utilities, electrical testing companies, and consulting firms. In addition to his consultation work in the electri-calpowerindustryMr.CadickistheauthorofCables and Wiring, The Electrical Safety Handbook, and of numerous professional articles and technical papers.


NFPA 70E 2000 Update

NETA World, Fall 2001 Issue

by John Cadick, P.E.Cadick Corporation

Figure 1 — NFPA 70E 2000

Since its first printing in 1981, NFPA 70E has served as a central staple for the establishment of electrical safety programs.Usedby theOccupational Safety andHealthAdministration (OSHA) as the basis for federal electrical safety rules, 70E has consistently been at the leading edge of electrical safety program implementation. The release of the 2000 edition of this document includes some of the most sweeping changes that have occurred in electrical safety since RalphLeefirstreleasedhisseminalresearchpapers.

This article describes many of the key changes that are introduced in 70E 2000. Of particular interest are the methods for the calculation of flash boundaries and flash protection. These methods are based on significant research performed during the last half of the 1990s. This research is continuing into the new millennium; consequently, substantial changes and improvements in electrical safety are to be expected over the next ten years.

OSHA and NFPA 70ETwo of the frequent questions received about NFPA 70E

are, “Do we have to follow 70E?”and “Will OSHA enforce 70E?” Such questions are usually asked by someone who is tryingtoexpendtheminimumpossibleeffortrequiredunderthe law. These individuals realize that OSHA Subpart S is a more simple standard to follow. I respond in one or more of four basic ways: 1) We are trying to create a safe workplace, 2) OSHA used 70E as the starting place for Subpart S, 3) If you adopt it, OSHA will enforce it, and 4) OSHA is presently looking into adopting 70E by reference.

We are trying to create a safe workplaceWe must always remember that the OSHA rules are, by

definition, minimum standards. While strict adherence to OSHA may improve electrical safety, such adherence does not guarantee optimum safety. For example, OSHA Subpart S says nothing about specific arc flash protection require-ments, and even Subpart R is somewhat vague, referencing only what an employee is not allowed to wear.

OSHA Subpart S has been introduced over a twenty-year period starting in 1981, with the most recent change being a major modification to paragraph 137 in 1994. NFPA 70E, on the other hand, is revised approximately every three years. This most recent revision, after five years, was a major one that incorporated a number of significant changes in tech-nology and world-wide regulations. 70E will always provide the greatest level of protection for personnel and should be used regardless of the status of the OSHA rules.

The OSHA Act makes it very clear that every employer must provide the maximum degree of electrical safety. As one very large mining firm puts it, “Zero incidents and beyond!!” Since 70E is the clear leader in electrical safety regulations, it just makes good common sense to adopt it for your company’s safety rules.

OSHA used 70E as the starting place for the Electrical Safety Work Practices Rule

The first release of 1910-331 through 335 was almost a verbatim copy of Part II of NFPA 70E. From the beginning then, OSHA has made it clear that, at least by reference, they recognized the importance of 70E.

In fact, OSHA maintains nonvoting membership on the NFPA 70E working group. This means that OSHA has at least some input to all of 70E’s provisions


If you adopt it, OSHA will enforce itNothing is so dangerous as the failure to follow a safety

procedure. During investigations, OSHA will often cite failure to follow an extant safety procedure. Even if the procedure is not one stated in the OSHA rules, if it is dis-obeyed, OSHA will cite it.

OSHA is presently looking into adopting 70E by reference

NFPA has submitted a written request to OSHA asking that NFPA 70E be adopted by reference. OSHA has responded by indicating their interest and asking the NFPA • Addmoredetailtotheirrequest.• Compile incidentdatawhichsupportsOSHA’sadop-

tion of 70E.• Encourageindustryandalliedagenciestosupportthe

request.

The 70E task group has responded by

• Formulating a comparison between 70E and OSHA1910SubpartSand1926SubpartK.

• Compiled incidentdata supportingOSHA’s adoptionof 70E.

• Solicitinglettersofsupportfromtheelectricalindustrygiants. So far four letters of support have been received and three more are promised.

While nothing is certain at this point in time, OSHA has expressed a strong interest in adopting 70E by reference. Thiswouldmeanthat70Ebecomes,ineffect,theOSHArules for electrical safety.

Based on the arguments brought forth in this section, 70E should be your first choice for basis of an electrical safety program.

Significant changes to NFPA 70E 2000 edition70E comprises six major parts:ForewordIntroductionPart 1 Installation Safety RequirementsPart 2 Safety-Related Work PracticesPart3Safety-RelatedMaintenancePracticesPart 4 Safety Requirements for Special Equipment

Each of the parts comprises several chapters with Part 2 also having several appendices. The most important changes are those found in the Introduction and Parts 1 through 4.

Miscellaneous changesIn general, the 2000 edition of 70E has been expanded

enormously. The definitions section of the Introduction has been extensively edited, and numerous definitions have been added. Definitions for the various hazardous classifications have been reduced and/or moved to Part 1. A quick scan of the section reveals that modifications have been made to almost one-half of the total with many new ones being added.

Of particular interest is the addition of the definitions for approach boundaries. The limited, restricted, and prohibited approach boundaries are clearly defined. Calculating them is covered in Part 2 and the Appendices for Part 2.

Changes to Part 1Part 1 of NFPA 70E covers the safety requirements for

design and installation of electrical systems. It comprises six chapters. Chapters 1, 2, and 3 introduce general safety requirements such as suitability for purpose. Chapter 4 cov-ers specific purpose equipment such as electric signs, cranes, elevators, and other such facilities. Chapters 5 and 6 cover hazardous locations in some detail.

Note that all of Part 1 is based on the provisions of the National Electrical Code - NFPA 70.

Chapter 1Chapter 1 has been extensively edited since the 1995

edition. All of the sections are still essentially the same. Two paragraphs are of particular importance since they have not changed substantially. Paragraph 1-3.4 and 1-3.5 require that protected equipment be properly coordinated and that it be capable of interrupting the current to which it will be subjected.

Chapter 2This chapter covers wiring design and protection and

has been expanded substantially with a great deal of detail being added in several places. Part 2.5, for example, covers overcurrent protection and has been modified dramatically in at least two places:1. The under 600 volt protection requirements have been

edited significantly. 2. The over 600 volt protection requirements have had al-

most one-half column of new requirements added since the last version.

Chapters 3 and 4The wiring methods, components, and equipment for

general use chapter (Chapter 3) has been edited in 70 to 80 percent of its sections.

The specific purpose equipment and installations chapter has also been modified although not as much as Chapter 3. It should be noted that the information covered in Chapter 4 addresses the installation and design safety requirements. The special equipment sections of Part 4 cover the special safety precautions required for systems such as batteries, cranes, and other apparatus.


Chapter 5Here we find some of the most important and sweeping

changes in the 2000 edition of 70E. Installation require-ments for hazardous locations have long been a source of confusion for electrical personnel. Now, as we enter the 21st century,thestandardsthathavebeenusedintheUnitedStates are being augmented by IEC standards. Although a detailed coverage of these standards is beyond the scope of this paper, Figure 2 illustrates some of the key relationships between the Division (NEC) and Zone (IEC) systems. This tablewaspresentedandexplainedbyMr.Vince Rowe of Ramco Electrical Con-sultingLtd.atthe2001IEEEElectricalSafety Workshop in Toronto Canada.

In the 2000 Edition of 70E both the NEC 70 Division method and the IEC Zone method of hazardous location classification are covered in detail. This is consistent with the change that was made in the 1999 NEC which allows the use of eithersystemintheUnitedStates.

In any event, this chapter has been extensively modified and will probably be modified more in the future as the North

American standards gradually move toward and merge with the IEC standards.

Chapter 6Chapter 6 of Part 1 covers special systems such as me-

dium- and high-voltage (over 600 volts), emergency systems, fire-alarmsystems,andothers.Glancingthroughthissec-tion shows that almost every paragraph has been extensively modified in the 2000 edition.

Changes to Part 2Arguably, the biggest changes throughout the entire

document are found in Part 2. An enormous amount of research has been done in electrical safety-related work practices during the last decade of the 20th century. The principle examples of this research shows up in the cal-culation of approach distances and arc flash protection requirements.

Approach Boundaries

AsshowninFigure3,NFPA70Edefinesfourdifferentapproach boundaries for personnel safety. Note that the flash boundary is shown as a dashed line because, as I will

Figure 3 — NFPA 70E Approach Boundaries

Acceptable Equipment Comparison for Class I Locations Zone System Division System Intrinsically safe, ia Equipment acceptable in Zone 0, Class I, Div. 1 Powder filled q Flameproof d Pressurized p Oil immersed o Increased safety e Intrinsically safe ib Encapsulation m

Equipment acceptable in Zone 0 Equipment acceptable in Zone 1, Class I, Div. 2 Non-sparking n Non-incendive Other electrical apparatus*

*”Other electrical apparatus” means electrical apparatus complying with the requirements of a recognized standard for industrial electrical appa-ratus that does not in normal service have ignition-capable hot surfaces and does not in normal service produce incendive arcs or sparks.

Zone 0

Zone 1

Zone 2

Division 1

Division 2

Class I, Div. 1Intrinsically safe i,ia

Class I, Div. 1Class I, Div. 2Flameproof dPressurized pIntrinsicallysafe ibOil immersed oIncreased safety ePowder filled qNon-sparking nEncapsulation mNon-incendiveOther electricalapparatus*

Figure 2 — Division vs. Zone method of hazardous locations

Figure 4 — Approach boundaries (Table 2-1.3.4 from NFPA 70E 2000 Edition)

(1) (2) (3) (4) (5)

Limited Approach Boundary

Nominal SystemVoltage (Ph-Ph)

0 to 5051 to 300301 to 750

751 to 15 kV15.1 kV to 36 kV36.1 kV to 46 kV

46.1 kV to 72.5 kV72.6 kv to 121 kV138 kV to 145 kV161 kV to 169 kV230 kV to 242 kV345 kV to 362 kV500 kV to 550 kV765 kV to 800 kV

Exposed MoveableConductor

Not specified10 ft 0 in10 ft 0 in10 ft 0 in10 ft 0 in10 ft 0 in10 ft 0 in10 ft 8 in11 ft 0 in11 ft 8 in13 ft 0 in15 ft 4 in19 ft 0 in23 ft 9 in

Exposed FixedConductor

Not specified3 ft 6 in3 ft 6 in5 ft 0 in6 ft 0 in8 ft 0 in8 ft 0 in8 ft 0 in10 ft 0 in11 ft 8 in13 ft 0 in15 ft 4 in19 ft 0 in23 ft 9 in

Restricted ApproachBoundary (Includes

Inadvertent Movement)

Not specifiedAvoid contact

1 ft 0 in2 ft 2 in2 ft 7 in2 ft 9 in3 ft 3 in3 ft 5 in3 ft 7 in4 ft 0 in5 ft 3 in8 ft 6 in11 ft 3 in14 ft 11 in

Prohibited Approach Boundary

Not specifiedAvoid contact

0 ft 1 in0 ft 7 in0 ft 10 in1 ft 5 in2 ft 1 in2 ft 8 in3 ft 1 in3 ft 6 in4 ft 9 in8 ft 0 in10 ft 9 in14 ft 5 in


describe later, its actual location varies as a function of avail-able short-circuit duty. The following paragraphs describe these changes.

Limited BoundaryThe limited boundary is for unqualified personnel. No un-

qualified person may approach any exposed energized con-ductor any closer than the limited approach boundary. (Note that OSHA defines a qualified person as one who is familiar with and trained in the operation and safety hazards of the equipment that he is working on.) The limited approach boundary is determined by referring to Table 2-1.3.4 in NFPA 70E, page 51 (2000 Edition). This table is reproduced in Figure 4.

Note that in the 2000 Edition NFPA has added the concept of movable or fixed conductors. In the 2000 edition unqualified workers may approach nonmoving conductors (fixed buswork, for example) more closely than those which may move (overhead lines, for example).

Restricted BoundaryGenerally,qualifiedpersonsarenotallowedtoapproach

exposed, energized conductors any closer than the restricted approach boundary unless they are wearing appropriate personal protective equipment (PPE) and they have a writ-ten, approved plan for the work they are to perform. They must break the restricted boundary only to the extent that is absolutely necessary to perform their work. The restricted boundary is determined using Table 2-1.3.4 in NFPA 70E, page 51 (2000 Edition).

Prohibited BoundaryCrossing the prohibited approach boundary (qualified

personnel only) is considered the same as actually contact-ing the exposed energized part. In addition to the require-ments for restricted boundary approach, personnel must perform a risk assessment before the prohibited boundary is crossed. The prohibited approach boundary is determined by referring to Table 2-1.3.4 on page 51 of NFPA 70E (2000 Edition).

Flash Protection BoundaryThe radiant energy released by an electric arc is capable of

maiming or killing a human being at distances of up to ten or even twenty feet. In addition to radiant heat, the molten material and objects ejected by the electrical blast can also be lethal. The flash protection boundary is the closest approach allowed by qualified or unqualified persons without the use of arc protection PPE. For systems under 600 volts ac, 70E sets up two possible ways to calculate the flash boundary.1. For locations with a total fault exposure of less than

5000 ampere-seconds (fault current in amperes multi-plied by clearing time in seconds), a flash boundary of four feet may be used.

2. Above 5000 ampere-seconds, or under engineering su-pervision for all levels, the following formulas may be used:

Where:DC = The flash boundary radiusMVAbf = TheboltedfaultMVAatthepoint of exposureMVA = ThemaximumfaultMVAfromthe transformer feeding the circuitT = The time of exposure (based on protective device operation)

Equation 1 provides generally smaller distances because it is based on more pertinent data — e.g. the fault duty at the pointofexposure(MVAbf ) as opposed to the transformer faultduty(MVA).

For voltage levels in excess of 600 volts, other formulas may be used. The flash boundary is defined as that distance at which the worker is exposed to 1.2 cal/cm2 for more than 0.1 seconds or 1.5 cal/cm2 for less than 0.1 seconds.

In summary for flash boundary:• Whenanenergizedconductorisexposed,absolutelyno

one may approach closer than the flash boundary with-out wearing appropriate arc protection.

• TheapplicationofEquation1willprovidethesmallerflash boundaries.

• Equation1maynotbeappliedwithoutanaccurate,up-to-date, short-circuit analysis at the point of exposure.

• If the flash boundary is smaller than the limited ap-proach boundary, the limited approach boundary is the closest that unqualified persons may approach.

Arc Flash CalculationsNFPA 70E recognizes that some workers may be re-

quired to cross approach boundaries in the day-to-day performance of their job. Voltage measurement, for example, will often require that a worker approach a potentially en-ergized conductor.

Empirical Data CalculationsAs stated previously, significant, new research has been

done relative to the amount of energy created by and re-ceived from an electrical arc. Doughty, Neal, and Floyd for example have developed empirical formulas for certain electrical arc events. In open air their research shows that the incident energy received from an electrical arc can be calculated by:


Where:EMA = Maximumopenarcincidentenergy (cal/cm2)DA = Distance from arc electrodes in inches 9tA = Arc duration in secondsISC = Bolted fault short-circuit current in kiloamperes

Note the following restrictions on Equation 3:1. Circuit voltage is 600 volts or below (line-to-line volt-

age).2. Fault currents (ISC) are greater than 16 kA and less than

50 kA.3. Distances (DA) must be greater than or equal to 18

inches.

It is interesting to note that this empirically developed formula very closely matches the theoretical inverse-square law. Research of this type has shown that the actual arc energy received will be greater if the arc is contained, or focused, by its environment. When Doughty, Neal, and Floyd enclosed their arc in a 20-inch square box with one side open, they found that the arc energy increased as given by:

Where:EMB= Maximumarc-in-a-box incident energy (cal/cm2)DB = Distance from arc electrodes in inches 9tB = Arc duration in secondsISC = Bolted fault short-circuit current in kiloamperes

Software SolutionsAt least two software solutions are available for calcu-

lation of incident arc energy. ARCPRO is a commercial softwareprogramwritteninMicrosoftWindows.FLUXisa DOS-based, freeware program written by Alan Privette, P.E.FLUXisavailablefordownloadatseverallocationsonthe internet including the Cadick Corporation website at http://www.cadickcorp.com.

Selecting Protective ClothingAfter the incident energy that will be received is calcu-

lated, the arc-clothing may be selected by comparing the arc thermal performance value (ATPV) or EBT. The ATPV represents maximum amount of incident energy that a given piece of clothing will attenuate to a “just-curable burn.” This value is determined by the clothing manufacturer using methodsdescribedinASTMstandardF1959.TheEBT valueisdeterminedusingASTMPS58.Thisvalueisused

when the ATPV cannot be deter-mined due to fabric break open.

A simplified approach to PPE selection

The 2000 Edition of 70E provides a simpler method for the selection of PPE. Although this technique is arguably overly-conservative, it can provide quick, sufficient solutions for some facilities.

Step 1 — Identify the hazard categoryNFPA Table 3-3.9.1 lists dozens of

typical tasks that may be encountered in an industrial/commercial power system. Figure 5 is a partial reproduc-tion of that table.

Consider, for example, working on an energized part in a 480 volt switchboard. Such a task is a Hazard/Risk Category 2*. The * means that in addition to the other clothing or PPE required for a Category 2, the worker must also use a double-layer switching hood and ear protection. Figure 5 — NFPA 70E Table 3-3.9.1 (partial reproduction)

Table 3-3.9.1 Hazard Risk Category Classifications

Task (Assumes Equipment Is Energized, and Work Is Hazard/Risk V-Rated V-ratedDone Within the Flash Protection Boundary) Category Gloves Tools

Panelboards rated 240 V and below — Notes 1 and 3 __ __ __Circuit breaker (CB) or fused switch operation with covers on 0 N NCB or fused switch operation with covers off 0 N NWork on energized parts, including voltage testing 1 Y YRemove/install CBs or fused switches 1 Y YRemoval of bolted covers (to expose bare, energized parts) 1 N NOpening hinged covers (to expose bare, energized parts) 0 N NPanelboards or Switchboards rated>240 V and up to 600 V (with molded case or insulated case circuit breakers) — Notes 1 and 3 __ __ __CB or fused switch operation with covers on 0 N NCB or fused switch operation with covers off 1 N NWork on energized parts, including voltage testing 2* Y Y600 V Class Motor Control Centers (MCCs) — Notes 2 (except as indicated) and 3 __ __ __CB or fused switch or starter operation with enclosure doors closed 0 N NReading a panel meter while operating a meter switch 0 N NCB or fused switch or starter operation with enclosure door open 1 N NWork on energized parts, including voltage testing 2* Y YWork on control circuits with energized parts 120 V or below, exposed 0 Y Y


Under certain conditions theHRCmay be reducedby one level. For example, Note 3 (which applies to our previously selected example) tells us that if the available fault current is less than 10,000 amperes, the HRC may be reduced by one level. Thus, instead of an HRC 2*, we would select an HRC 1*.

Step 2 — Select the PPE from the PPE matrix

Figure 6 is a partial reproduction of 70E 2000 Table 3-3.9.2. This table allows the user to select the type of PPE required for the task at hand. For our example, the worker is required to wear an untreated, natural-fiber tee-shirt as well as untreated, natural fiber long pants. (Note 6 allows the elimination of the long pants provided the FR clothing has an ATPV of at least 8.) The worker must also wear a long-sleeve FR shirt and pants. Note 7 allows the worker to substitute an FR coverall for these requirements. Please note that this example is intended to illustrate the method, not serve as a short-cut for going through all of the neces-sary calculations.

Step 3 — Refer to NFPA 70E Table 3-3.9.3 to confirm the adequacy of FR Clothing

70E Table 3-3.9.3 is shown here as Figure 7. This table gives the minimum ATPV (or EBT) for the various catego-ries defined in Table 3-3.9.2. A couple of points may help to clarify this table:• Thetotalweightcolumnistypical.Agivenmanufactur-

er’s clothing may be more or less.• TheATPVthatisgivenisminimumfortheparticular

hazard/risk category.

Changes to Part 3Very little has been changed since the 1995 version. Es-

sentially, the only changes were those required by changes to other parts. For example, the substantial increase in the hazardous location section (Part 1 Chapter 5) required that some changes be made in Part 3 to reference properly.

Other than the various NETA standards, NFPA 70B continues to be the sole regulatory source of information for maintenance related activities.

Changes to Part 4The 2000 edition is the first time that anything has ap-

peared in Part 4. In other words — everything in Part 4 is new to this edition. Procedures, equipment, and training requirementsarelaidoutforfourdifferenttypesofspecialequipment including:• Electrolyticcelllines• Batteriesandbatteryrooms• Lasers• Powerelectronicequipment.

This entire section should be used as a ready reference for these special types of equipment.

ConclusionNFPA 70E is and will continue to be the most up-to-

date and ready reference for regulatory information covering electrical safety programs. For additional information, the readerisdirectedtotwodifferentindustrytextsonelectri-cal safety:

The Electrical Safety Handbook byJohnCadick(McGraw-Hill, currently in 2nd edition)Electrical Safety in the Workplace by Ray Jones, P.E. and Jane Jones (NFPA)

Table 3-3.9.2 Protective Clothing and Personal Protective Equipment (PPE) Matrix

Protective Clothing & Equipment Protective Systems for Hazard/Risk Category

Hazard/Risk -1 0 1 2 3 4 Category (Note 3) NumberUntreated __ __ __ __ __ __Natural Fibera. T-shirt X X X X(short sleeve)b. Shirt X

(long-sleevec. Pants X X X X X X(long) (Note 4) (Note 6)

FR Clothing __ __ __ __ __ __(Note 1)a. Long-sleeve X X X Xshirt (Note 9)

b. Pants X X X (Note 4) (Note 6) (Note 9) (Note 5)

c. Coverall X X (Note 5) (Note 7) (Note 9)

d. Jacket, parka, or rainwear AN AN AN AN

FR Protective __ __ __ __ __ __Equipmenta. Flash suit jacket X(2-layer)

Figure 6 — NFPA 70E Table 3-3.9.2 (partial reproduction)


Other references:“PredictingIncidentEnergytoBetterManagetheElec-

tric Arc Hazard on 600 V Power Distribution Systems,” IEEEpaperbyRichardLDoughty,ThomasE.Neal,andH.LandisFloyd.

Please note that tables are not reproduced in their en-tirety. Refer to NFPA 70E for full details.

A registered professional engineer and the founder and president of the Cadick Corporation, John Cadick has specialized for over three decades in electrical engineering, training, and management. His consult-ingfirm,basedinGarland,Texas,specializesinelectricalengineeringand training and works extensively in the areas of power system design and engineering studies, condition-based maintenance programs, and electrical safety. Prior to creating the Cadick Corporation and its prede-cessor Cadick Professional Services, he held a number of technical and managerial positions with electric utilities, electrical testing companies, and consulting firms. In addition to his consultation work in the electri-calpowerindustryMr.CadickistheauthorofCables and Wiring, The Electrical Safety Handbook, and of numerous professional articles and technical papers.

Table 3-3.9.3 Protective Clothing Characteristics

Typical Protective Clothing Systems

Hazard Risk

Category

0

1

2

3

4

Clothing Description (Number of clothing layers is

given in parentheses)

Untreated cotton (1)

FR shirt and FR pants (1)

Cotton underwear plus FR shirt and FR pants (2)

Cotton underwear plus FR shirt and FR pants plus FR coverall (3)

Cotton underwear plus FR shirt and FR pants plus double layer switching coat and pants (4)

Total Weightoz/yd2

4.5 - 7

4.5 - 8

9 - 12

16 - 20

24 - 30

Minimum Arc Thermal Performance Exposure

Value (ATPV)* or Breakopen Threshold Energy (EBT)*

Rating of PPE cal/cm2

N/A

5

8

25

40

*ATPV is defined in the ASTM P S58 standard arc test method for flame resistant (FR) fabrics as the incident energy that would just cause the onset of a second degree burn (1.2 cal/cm2). EBT is reported according to ASTM P S58 and is defined as the highest incident energy which did not cause FR fabric breakopen and did not exceed the second-degree burn criteria. EBT is reported when ATPV cannot be measured due to FR fabric breakopen.

Figure 7 — NFPA 70E Table 3-3.9.3


Protective Devices Maintenance as it Applies to the Arc/Flash Hazard


by Dennis K. Neitzel, C.P.E.AVO International Training Institute

One of the key components of the flash hazard analysis which is required by NFPA 70E-2000, Part II, paragraph 2-1.3.3 is the clearing time of the protective devices, primarily circuit breakers and protective relays. Fuses, although they are protective devices, do not have operating mechanisms that would require periodic maintenance; therefore, this article will not address them. The primary focus of this article will be the maintenance issues for circuit breakers and protective relays.

Molded-case and low-voltage, power circuit breakers(600 volts or less) will generally clear a fault condition in three to eight cycles. To be conservative a clearing time of eight cycles should be used. The majority of older medium-voltage circuit breakers (2300 volts or greater) will clear a fault in around eight cycles with the newer ones clearing in three to five cycles. Protective relays will generally add approximately three to four cycles to the clearing time of the medium-voltage circuit breaker. Where correct maintenance and testing are not performed, extended clearing times could occur,creatinganunintentionaltimedelaythatwillaffectthe results of flash hazard analysis.

All maintenance and testing of the electrical protective devices addressed in this article must be accomplished in accordance with the manufacturer’s instructions. The NETA Maintenance Testing Specifications for Electrical Power Dis-tribution Equipment and Systems is an excellent source of information for performing the required maintenance and testing of these devices. Visit the NETA website for more information at http://www.netaworld.org.

This article will address some of the issues concerning the correct maintenance and testing of these protective devices. It will also address how protective device maintenance re-lates to the electrical arc/flash hazard.

Molded-Case Circuit BreakersGenerally,maintenanceonmolded-casecircuitbreakers

is limited to the correct mechanical mounting, electrical connections,andperiodicmanualoperation.Mostlighting,appliance, and power panel circuit breakers have riveted frames and are not designed to be opened for internal inspection or maintenance. All other molded-case circuit breakersthatareULapprovedarefactory-sealedtopreventaccess to the calibrated elements. An unbroken seal indicates that the mechanism has not been tampered with and that it shouldfunctionasspecifiedbyUL.AbrokensealvoidstheULlistingandthemanufacturers’warrantyofthedevice.Inthis case, the integrity of the device would be questionable. The only exception to this would be a seal being broken by a manufacturer’s authorized facility.

Circuit breakers installed in a system are often forgotten. Even though the breakers have been sitting in place supply-ing power to a circuit for years, there are several things that can go wrong. The circuit breaker can fail to open due to a burned out trip coil or because the mechanism is frozen due to dirt, dried lubricant, or corrosion. The overcurrent device can fail due to inactivity or a burned out electronic component.Manyproblemscanoccurwhenmaintenanceis not performed and the breaker fails to open under fault conditions. This combination of events can result in fires, damage to equipment, or injuries to personnel.

Low-Voltage, Power Circuit BreakersLow-voltage,power circuitbreakers aremanufactured

under a high degree of quality control, of the best materials available, and with a high degree of tooling for operational accuracy.Manufacturer’stestsshowthesecircuitbreakersto have durability beyond the minimum requirements of standards. All of these factors give these circuit breakers a very high reliability rating. However, because of the varying application conditions and the dependence placed upon


them for protection of electrical systems and equipment as well as the assurance of service continuity, inspections and maintenance checks must be made on a regular basis. Several studies, including those by IEEE, have shown that low-voltage power circuit breakers which were not maintained within a five-year period, have a 50 percent failure rate.

Maintenance of these breakerswill generally consistof keeping them clean and appropriately lubricated. The frequency of maintenance will depend to some extent on the cleanliness of the surrounding area. If much dust, lint, moisture, or other foreign matter were present then, obvi-ously, more frequent maintenance would be required.

Medium-Voltage, Power Circuit BreakersMostoftheinspectionandmaintenancerequirementsfor

low-voltage, power circuit breakers also apply to medium-voltage,powercircuitbreakers.Manufacturersrecommendthat these breakers be removed from service and inspected at least once per year. They also state that the number and severity of interruptions may indicate the need for more frequent maintenance checks. Always follow the manufac-turer’sinstructionsbecauseeverybreakerisdifferent.

Protective RelaysRelays must continuously monitor complex power circuit

conditions, such as current and voltage magnitudes, phase angle relationships, direction of power flow, and frequency. When an intolerable circuit condition, such as a short cir-cuit (or fault) is detected, the relay responds and closes its contacts and the abnormal portion of the circuit is deener-gized via the circuit breaker. The ultimate goal of protective relaying is to disconnect a faulty system element as quickly as possible. Sensitivity and selectivity are essential to ensure that the right circuit breakers are tripped at the right speed to clear the fault, minimize damage to equipment, and to reduce the hazards to personnel.

Flash Hazard AnalysisAs noted at the beginning of this article, NFPA 70E-

2000 requires a flash hazard analysis be performed before anyone approaches exposed electrical conductors or circuit parts that have not been placed in an electrically safe work condition. In addition, Paragraph 2-1.3.3.2 requires a flash protection boundary to be established. All calculations for determining the incident energy of an arc and for estab-lishing a flash protection boundary require the arc clearing time. This clearing time is derived from the engineering coordination study which is based on what the protective devices are supposed to do.

Maintenanceisacriticalpartoftheflashhazardissue.Evidence has proven that inadequate maintenance can cause unintentional time delays in the clearing of a short-circuit condition. If, for example, a low-voltage, power circuit breaker had not been operated or maintained for several years and the lubrication had become sticky or hardened, the

circuit breaker could take several additional cycles, seconds, minutes, or longer to clear a fault condition. The following is a specific example.

If a flash hazard analysis is performed based on what the system is suppose to do, let’s say five-cycle clearing time, and there is an unintentional time delay, due to a binding mechanism, and the breaker clears in 30 cycles, the worker could be seriously injured or killed because he/she was underprotected.

If the calculation is performed for a 20,000 ampere fault, 480 volts, three-inch arc gap, the worker is 18 inches from the arc, with a five-cycle clearing time for a three-phase arc in a box (enclosure), the results would be approximately 6.5 cal/cm2 which would require an arc/flash Category 2 protec-tion based on NFPA 70E-2000, Part II, Table 3-3.9.3.

Figure 1 uses the heat flux calculator (developed by Alan Privette) and the values above for a five-cycle clearing time. This value of 1.89431 cal/cm2 is based on a single-phase arc in open-air. As a general rule of thumb, the value of 1.89431 would be multiplied by a factor of two for a single-phase arc in a box (2 x 1.89431 = 3.78862 cal/cm2 – Category 1) and by a factor of 3.4 for a multiphase (three-phase) arc in a box (3.4 x 1.89431 = 6.440654 cal/cm2 – Category 2).

If the clearing time is increased to 30 cycles (Figure 2) then the results are approximately 38.7 cal/cm2, which requires an arc/flash Category 4 protection. The value of 11.36586 cal/cm2 is based on a single-phase arc in open-air. Again, as a general rule of thumb, the value of 11.36586

*************************************************************This program is made available to the general public for the purpose of calculating heat flux received at a surface some distance from an electric arc. The use of this program is the responsibility of the user. The author makes no warranty to the accuracy of the results and accepts no responsibility any damage that may arise from its use.*************************************************************

Enter the arc current(amps) ? 20000Enter the arc gap(inches) ? 3Enter the supply voltage(volts) ? 480Arc column area 43.03264 sq. inchesArc column cir. 14.34421 inchesArc diameter 4.565908 inchesArc power in watts - 1781250Arc power in calories/sec - 425540.6Heat flux on surface of arc 1533.146 cal/cm^2-secEnter the distance from the arc to the receiving surface ? 18Transfer Shape Factor 1.482744E-02Heat Flux at Receiving Surface 22.73263 cal/cm^2-secEnter the number of cycles for the arc duration ? 5Arc Duration 8.333001E-02 secondsTotal Calories per Sq. Cm. at Receiving Surface 1.89431

Do You Wish To Run Another Case? (Y or N) ?

Calculation with a Five-Cycle Clearing Time


would be multiplied by a factor of two for a single-phase arc in a box (2 x 11.36586 = 22.73172 cal/cm2 – Category 3) and by a factor of 3.4 for a multiphase (three-phase) arc in a box (3.4 x 1.89431 = 38.643924 cal/cm2 – Category 4).

Therefore, as can be seen, maintenance is extremely im-portanttoanelectricalsafetyprogram.Maintenancemustbe performed according to the manufacturer’s instructions in order to minimize the risk of having an unintentional time delay in the operation of the circuit protective devices.

SummaryWith the appropriate mixture of common sense, training,

manufacturers’ literature, and spare parts, correct mainte-nance can be performed and power systems kept in a safe, reliable condition. Circuit breakers, if installed within their ratings and correctly maintained, should operate trouble-free for many years. However, if operated outside of their ratings or without maintenance, catastrophic failure of the power system, circuit breaker, or switchgear can occur caus-ing not only the destruction of the equipment but serious injury or even death of employees working in the area.

DennisK.Neitzel,C.P.E.,DirectorofAVOTrainingInstitute,Dallas,Texas, earned his bachelor’s degree in electrical engineering management and his master’s in electrical engineering applied sciences from Colum-biaPacificUniversity.HeearnedhisCertifiedPlantEngineer(C.P.E.)throughtheAFEandhisCertifiedElectricalInspector-Generalthrough

theIAEI.HehasbeenaPrincipleCommitteeMemberfortheNFPA70E, Standard for Electrical Safety Requirements for Employee Workplaces since 1992 and is co-author of the Electrical Safety Handbook, Second Edition,McGraw-HillPublishers.HeisamemberoftheInstituteofElectrical and Electronics Engineers, the American Society of Safety Engineers, the Association for Facilities Engineering, the International Association of Electrical Inspectors, and the National Fire Protection Association.

*************************************************************This program is made available to the general public for the purpose of calculating heat flux received at a surface some distance from an electric arc. The use of this program is the responsibility of the user. The author makes no warranty to the accuracy of the results and accepts no responsibility any damage that may arise from its use.*************************************************************

Enter the arc current(amps) ? 20000Enter the arc gap(inches) ? 3Enter the supply voltage(volts) ? 480Arc column area 43.03264 sq. inchesArc column cir. 14.34421 inchesArc diameter 4.565908 inchesArc power in watts - 1781250Arc power in calories/sec - 425540.6Heat flux on surface of arc 1533.146 cal/cm^2-secEnter the distance from the arc to the receiving surface ? 18Transfer Shape Factor 1.482744E-02Heat Flux at Receiving Surface 22.73263 cal/cm^2-secEnter the number of cycles for the arc duration ? 30Arc Duration .49998 secondsTotal Calories per Sq. Cm. at Receiving Surface 11.36586

Do You Wish To Run Another Case? (Y or N) ?

Calculation with a Thirty-Cycle Clearing Time

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Electric Arc Flash Protective Clothing


by Paul HartmanSigma Six Solutions

Figure 1

Definitions Arc Thermal Performance Value (ATPV): This value is

presented in calories per square centimeter and represents the maximum capability for arc flash protection of a par-ticular garment. This rating also applies to fabrics. However, a garment made from more that one layer of arc flash rated fabric will have a calories per square centimeter rating greater than the sum of the ATPV ratings of the original fabrics. The calories per square centimeter rating of most arc flash protective suits, coveralls, and coats is commonly sewn into the fabric in large letters on the outside of the garment.

Flame Resistant (FR): “Flame resistant” can describe a fabric naturally resistant to burning but also can represent a material with special treatment applied to the fabric. Occasionally, the letters FR are used to represent “flame retardant.” This can lead to some confusion because a flame-retardant treated fabric is flame resistant, but a flame-resis-tant fabric is not necessarily flame retardant.

Flame Retardant: This term could be used to describe a fabric made up of a flammable fabric treated in such a way that it will provide arc flash protection.

Fabric Weight: This is usually represented in one of two ways: ounces per square yard or grams per square meter. Both of these values essentially refer to the thickness of the fabric. The more ounces per square yard, the more material exists in the same square yard of fabric.

Heat Attenuation Factor (HAF): This is the amount of heat blocked by the fabric. Even though a fabric may be 100 percent flame resistant, that does not mean it will block all of the heat to which it is exposed. An HAF of 85 percent means that it will block 85 percent of the heat the fabric encounters. This applies to a short burst of arc flash heat – typically less than one second. In the event of prolonged heat exposure, the HAF would be much lower.

IntroductionAdvances in technology have definitely improved the arc

flash clothing options available to workers. It was not all that long ago – the 1980s – that the choice of flash protection was extremely limited, and few employers even had a policy on flash clothing. Today there are a dozen or so brand names of arc flash protection clothing, with some brands providing differentfabricsrangingfromfiveto13ouncespersquareyard fabric weight. These fabrics are available in an array of colors, weaves, and textures, as can be seen in Figure 1. As with all safety equipment, arc flash clothing is of no use to anyone unless it is being used at the time of an arc flash. This article addresses available fabrics to be worn by workers and the associated definitions of arc flash terms.


Calories per Centimeter Squared: This is a number identifying the amount of energy that can be delivered to a point at a particular distance from an arc flash. Once this value is known, the ATPV rating of the flash clothing required for work at that distance from the potential flash hazard is also known.

Energy Break-Open Threshold (EBT): Primarily, this addresses the physical strength of the fabric with respect to thermal energy and at what arc flash value the fabric will fail.

Personal Protective Equipment (PPE): This term is primarily used to describe all safety equipment used by personnel to protect personnel. This includes fall protection, confined space, electrical hazards, and so on.

Hazard Risk Category (HRC): This is a 2004 NFPA 70E rating of exposure levels for particular types of equip-ment. The values range from zero to four, with a zero HRC not requiring any ATPV-rated PPE. The minimum ATPV rating for Categories One through Four are as follows:

• Category One: five calories per square centimeter• Category Two: eight calories per square

centimeter• Category Three: 25 calories per square centimeter• Category Four: 40 calories per square centimeter

Overclothing: Any arc flash rated clothing with a HAF of less that 70 percent is considered overclothing. This means that the flash-rated clothing must be worn over a suitable undergarment to protect the wearer. Typically, the undergarments in this situation would be 100 percent cot-ton. Other undergarment fabrics may be required in special situations.

Arc Flash Clothing LabelsIn the past there were no real guidelines as to what the

manufacturers of arc flash clothing were required to place onthelabel.NewASTMstandardsmandateaminimumoutline of that which must be clearly printed on the label of arc flash rated clothing. Some manufacturers have made sure that workers know their product is not intended for arc flash protection, as can be seen in Figure 2.

ThelistforASTMflashclothinglabelrequirementsisas follows:

1.Manufacturer2. Care instructions3. Fabric fiber content4.Garmentsize5.Manufacturertrackingcode6.MeetsF1506FireRetardantStandards7. ATPV rating in calories per square centimeter

For some unknown reason, the HAF was not included on the label-requirement list. Some manufacturers include this value on the label anyway. The HAF should be evaluated when considering what types of arc flash PPE to purchase. This information, if not on the label, is readily available from the manufacturers.

Figure 3 shows a hard hat liner that had been in use for years. The label states that the outer shell of this liner is “Flame Retardant, until Washed or Dry Cleaned.” This garment was manufactured more than 15 years ago and met the standards of the day. The only issue here is that when a personlooksatthelabelthefirstthingtheyseeis“FLAMERETARDANT.” The fact that the inner part of the liner has no fire resistant characteristics is not clearly identified, and the smallest print on the tag identifies that the first time you wash this item it removes all flame protection.

Fabrics for Electric Arc Flash Protection100 Percent Cotton: It was not all that long ago that

plain old cotton was considered the appropriate protective clothing when an electrical arc exposure was present. The thinking was that cotton provided much better protection than polyester, nylon, acetate, and the like. This is true. However, along came products that soon made untreated cotton an undesirable fabric for these situations.

Flame-Retardant Treated 100 Percent Cotton: One such fabric available today is marketed under the trade name “Indura.” This fabric is made by Westex and is guaranteed to maintain flame retardant performance throughout the life of the garment. This fabric has an expected wear life of 50 to 75 home launderings. This means that five sets of shirts and pants, each worn once per week, will last 12 to16 months in the range of light- to severe-use conditions.

In Indura-engineered fabrics, the flame retardant chemi-cal impregnated on the cotton fiber core acts as a catalyst promoting the charring of the fabric. This accelerated char-

Figure 2


ring prohibits the support of combustion by reducing the fuel source. The flame retardant chemical acts in the solid phase to produce this char. The mechanism of action is not based on a gaseous process of extinguishing or “snuffing out” the flame.

It is very important that flame resistant fabrics be main-tained in a clean condition to realize their full protection potential.

Flame-Retardant Treated 88 Percent Cotton, 12 Percent Nylon: Previously, it was stated that nylon was an undesirable fabric for electric arc blast protection. With this blend there is a mechanical type reaction when it is exposed to excessive heat. The nylon melts and essentially fills up the gaps between the cotton fibers creating a more solid defense against the heat source. This fabric is sold under the trade names of “Banwear” (made by Itex) and “Indura UltraSoft” (made by Westex). Both of these products guarantee that the flame retardant performance of the fabric is maintained throughout the life of the garment. One can expect Banwear andInduraUltraSofttolast18to30monthswhenworndaily and home laundered once per week.

45 Percent Combed Cotton Fiber, 55 Percent Mod-acrylic: Modacrylic is a shortened name for “fibrousflame-retardant fiber.” By combining these two fibers the fabric “Firewear” is produced. Firewear is manufactured bySpringfieldLLC.Thesewovenfabricsrangeinweightfrom 5.5 to 9.5 ounces per square yard and are available in both twill and plain weaves. Firewear also is available in knits from 6.0 to 14.0 ounces per square yard. Before the fibrous flame-retardant fibers are exposed to heat and flames, they look and feel just like any other textile fiber. Uponexposuretoflames,areactionbegins:certainmolecu-lar components of the fiber emit non-combustible gas that is released through tiny pores in the fiber. This smothers the fire in much the same way that a fire extinguisher does. Thesegasesshutofftheoxygenfeedingtheflames,therebypreventing further burning. Firewear has an expected wear life of 18 to 30 months when worn daily and home laun-dered once per week.

93 Percent Nomex, Five Percent Kevlar, and Two Percent Antistatic Fiber: This long-winded description is most commonly know by its trade name “Nomex IIIA.” This is the latest and greatest of the Nomex line that has been manufactured by DuPont. Nomex IIIA is a lightweight, inherently flame-resistant fiber blend. It does tend to have a higher heat let-through rate and is not recommended for use around molten metals. This fabric is available in weaves from 3.3 to 7.5 ounces per square yard. Some weights are available in ripstop and twill weaves. Nomex IIIA has an expected wear life of 30 to 48 months.

60 Percent Kevlar, 40 Percent Polybenzimidizole: This blended fabric is marketed under the trade name of “PBI/Kevlar.” The polybenzimidizole fiber is manufactured by CelaneseAcetate;theKevlarfiberismadebyDuPont.

Care and CleaningA variety of flame-resistant fabrics are available in

today’s marketplace. Each fabric has unique wear, comfort, appearance, and durability characteristics. Each of these issues should be considered when making a flame-resistant garment purchase.

Industrial laundering creates more wear on a garment than home laundering. Also, it has been found that heavy facialgrowthhasanegativeeffectonwearlifeofacollaredshirt. Additionally, repeated abrasion of any type shortens wear life in the area on the garment where the abrasion occurs.

Indura should not be laundered with hypochlorite (chlo-rine) bleach because repeated exposure will break down the finishandisdestructivetothefabricandthecolor.Mostflame-resistant fabrics, including Nomex, bear instructions prohibiting the use of chlorine bleach because it is destruc-tive to the fabric strength and color even if flame resistance isnotaffected.

Paul Hartman has over 18 years experience in start-up, commissioning, maintenance, and training in power generation, including international projects inPakistan, Indonesia,Thailand,Brazil, andKorea.Hehasbeen an instructor for state certified continuing education programs. Paul is currently Vice President of Sigma Six Solutions. He is a regular contributor to NETA World and a frequent speaker at NETA’s Annual Technical Conference.

Figure 3


Corrective Measures to Arc Flash Problems —

Is It that Simple?NETA World, Fall 2004 Issue

by Ron WidupShermco Industries

IntroductionWith all the talk about the NFPA 70E, Hazard Risk

Analysis, IEEE 1584, and all of the associated elements related to arc flash hazards, what do you do when you dis-cover an arc flash hazard within your facility? Hint: Run like the wind…..

While at times it can be a very complicated (read: expen-sive) solution to solving your problem, more often than not it is, or can be, a simple solution. The following case studies are examples of how some arc flash hazards can be corrected withouttoomucheffort,andheck,youmightevenimpressyour boss (doubtful).

BackgroundOne of the first, and most basic, principles of an electrical

safety program is to identify and minimize hazards in an electrical system. One of the key elements to identifying these hazards is to quantify the electrical arc energy in the system, both magnitude and distance. An arc flash engineer-ing study will get you these values, but it won’t buy you a new pair of shoes.

If a worker is to work on or near exposed conductors that will not be in an electrically safe work condition,* a shock hazard analysis and flash hazard analysis are required.

*Electrically Safe Work Condition; Per NFPA 70E, Standard for Electrical Safety in the Workplace, 2004 Edition:

A state in which the conductor or circuit part to be worked on or near has been disconnected from ener-gized parts, locked/tagged in accordance with estab-lished standards, tested to ensure the absence of voltage, and grounded if determined necessary.

While personal protective equipment (PPE) manufac-turers make flash suits with arc ratings up to 100 cal/cm2, NFPA 70E does not have a Hazard Risk Category for incident energies above 40 cal/cm2. Working on energized circuits with energy levels in excess of 40 cal/cm2 should be avoided by all means necessary. If energized work must be performed on these circuits, steps should be taken to reduce the hazard before the work is to be performed. Although it would seem as though a 100 calorie Hazard Risk Category level might be one you could easily classify as the BOD, or “Big ‘Ol Dufus” category.

So if you have determined that a hazard exists, and have performed an arc flash study, you are on your way to protect-ing your workers from the hazards. But now that you know the hazards exist along with the quantifiable data, what’s next?HappyHour!OK,Idigress—afewexampleswithsolutions are outlined below.

Case Study ExamplesCase Study No. 12000 kVA Transformer With No Main Breaker

Invariably, just about any 1500 — 3000 kVA 480-volt unit substation transformer will have a high incident en-ergy level between the transformer secondary bushings and the main breaker line side bus. In this example, a 480-volt outdoor substation is fed from a 2000 kVA transformer. The transformer primary is protected with a 15 kV vacuum circuit breaker. The substation does not have a main breaker, only feeder breakers. For a diagram of this design, read “Engineering 101 — What NOT to do.”

After analysis, it was determined that the incident energy on the main bus was approximately 109 cal/cm2. At this level of incident energy and because the feeder breakers were not protected by a main breaker, none of the feeder breakers


could be racked in or out without being in violation of the requirements as established in NFPA 70E. And, one of the most prevalent comments from the owner of the equipment was, “Why, after 25 years, do you now tell me I cannot oper-ate those same breakers that I have been operating (racking in and out) for the last 25 years?”

The answer is, obviously, “Because.”OK,thatmaynotbeexactlytherightanswer,butbecause

we now know what the incident energies are, and because we now know we have to do something about it, and because we care about our employees (well, maybe the first shift employees) — it is because of these items that we need to fix it. So what’s the solution? The owner can’t change his substation out without going through a time intensive capital spending request with corporate, and he can’t just all-of-a-sudden stop racking breakers in and out. So, what is he to do?

Call the Coordination Police, Batman! This particular transformer was coordinated with the system to maintain maximum uptime without damaging the transformer, with a relay time-dial setting of 5.0. After analyzing the data, it was determined that a time-dial setting of 2.0 will still maintain system stability, allow for proper coordination, and will reduce the incident energy on the low-voltage bus from 109 cal/cm2 to about 40 cal/cm2. Viola! We are now down to a level at which we can get burned just enough to liveandtellaboutit!Missionaccomplished.

Case Study No. 2Racking In (or Out) A Main Breaker on a 2500 kVA Unit Substation

In this example, take the same situation as above, only now insert a main breaker on the 480-volt bus in a double-ended substation.Youhave now solved one of the twoproblems. The solution to one of the problems is that now you have put an overcurrent device between the transformer secondary and the feeder breaker main bus (with the main breaker). Problem number two, the incident energy on the line side of the main breaker to the transformer secondary bushings is still high. So now what?

Call the Coordination Police Batman! What?! Phone’s busy? Then call the electrical department! So what can the electricaldepartmentdoforyou?Let’stakealookatthesituation:• Youhavea13.8kVfusedswitchinfrontofa2500kVA

transformer• The transformer feeds a main breaker on one side of the

substation• The main breaker must be closed to get power to the

substation• The double-ended substation is configured for open-

transition operationGotit?Nowthinkabouttheoperationofthesubstation

— is there any reason to have the transformer energized before racking the breaker in or out? (insert Jeopardy theme here) No? Well good, because you have just changed one

simple plant procedure and reduced your exposure to the hazard. Because after all, if there is no electricity, there is no hazard, right? Almost…. It is not exactly “electrically safe,” but it is in a much safer condition than if you had it energized, yes?

As you can see from Diagram 1, at a distance of 36 inches the incident energy at the 13.8 kV switch primary is 4.5 cal/cm2, and on the load side of the switch it is 0.2 cal/cm2! Now jump to the 480-volt side of the transformer, line side of the main breaker, and it becomes 76.4 cal/cm2 at 24 inches — again a situation that you do not want any part of, unless you like to tan very quickly.

ThelessonforCaseNo.2?Turnitoff,Einstein.

Case Study No. 3The Case of the Slow Fuse — or How I Spent my Summer Vacation

In this example, check out Diagram 2, where there is a 10,000 kVA transformer fed from a 13.8 kV fused switch, which then feeds a medium-voltage main breaker, and ultimately feeds a medium-voltage motor control center

Diagram 1


(Emcee,See?)TheMCCfeedsanotherfusedswitch,whichthen feeds a 1000 kVA transformer, reactor, and variable frequencydrive(VFD-BigMoney)fora900hpmotor.Simple, right?

Diagram 2 Diagram 3

With all of those overcurrent devices, including switches, breakers, fuses, reactors, and lengths of cable you would think the power system would owe you a few incident energies. Sorry, it is not to be. Initially there was a s-l-o-w speed fuse in the 4.16 kV main switch for the VFD. How did we know it was slow fuse? It had a degree from Texas A&M(badTexasjoke).


Actually, when the application was changed to a stan-dard speed fuse, it was apparent that there was no room in Bryan-College Station for no slow-speed fuse. Check out the incident energies before and after the fuses were changed:

As Top Gun Maverick says “I feel the need, the need for speed.” Another interesting point of discovery, the incident energy is higher on the load side of the reactor than it is

right. I thought reactors were supposed to limit current, thereby limit the amount of incident energy. Not on my watch, soldier!

While these case studies are but a few of the thousands of

it shows that the issues don’t necessarily always involve

from the hazards of the electric arc may just be a simple one. Which, after all, is what it is all about….

Be Safe!

References:1. NFPA 70E, Standard for Electrical Safety in the Work-

place. Quincy, MA: National Fire Protection Associa-tion, 2004

2. Safety Basics, Handbook for Electrical Safety. St. Louis, MO: Cooper Bussman, Inc., Edition 2

Ron A. Widup, Executive Vice President/General Manager of Shermco Industries has over 20 years of experience in the low-, medium-, and high-voltage switchgear and substation market. He is a principal member of NFPA technical committee 70E (Standard for Electrical Safety in the Workplace) and a member of NEC Code Panel 11. He is past president of NETA and currently a member of the Board

Level IV Senior Test Technician.

Slow Fuse (Diagram 2) Standard Fuse (Diagram 3) Reactor Line Side 51.9 cal/cm2 Reactor Line Side 24.7 cal/cm2

Reactor Load Side 52.7 cal/cm2 Reactor Load Side 25.3 cal/cm2


Electrical Safety — Myths and Rumors


by David K. KregerElectrical Reliability Services

In my travels throughout these last years I have had op-portunity to present electrical safety as well as other types of technical training. I continue to be flabbergasted at some of the comments I hear from students or other supposedly “qualified” electrical workers regarding the requirements to maintain a safe work environment. Some examples of these questions and statements are given below, followed by appropriate answers.

1. OSHA has a new requirement to perform a hazard or risk analysis before beginning each job. This statement refers to CFR 29, 1910.132(d)(1), which

says: “The employer shall assess the workplace to deter-mine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE). If such hazards are present, or likely to be present, the employer shall: 1910.132(d)(1)(i) Select, and have each affectedemployeeuse,thetypesofPPEthatwillprotecttheaffectedemployee fromthehazards identified in thehazard assessment.”

This new requirement is not new at all. Since OSHA’s inception in the early 1970s, the entire premise has been to ensure, as much as possible, a safe work environment for employees. Each employer has an obligation to determine what hazards an employee may face on the job. Once the hazard has been identified, the employer has further obli-gation to provide the appropriate training, PPE, or other work procedures that would allow the employee to perform the task safely.

Specific to the electrical industry are several hazards of which qualified workers should be aware in order to be considered “qualified.” Shock and arc flash burns are the two primary hazards faced when working on or around energized electrical equipment. Therefore, the employer has an obliga-tion to identify possible shock hazards, identify possible flash burn hazards, and provide the appropriate tools, PPE, or

work procedures to mitigate these hazards. I will add that, even though the appropriate tools and PPE are available, the supposedly qualified worker may not know what to do with them. For example, I witnessed a 20-year veteran pull the insulating rubber gloves on over the leather gauntlets! When questioned, he responded, “I always wears them like that since the rubber part is the shock protection part and the leather inside keeps my hands from getting sticky.”

2. Insulated gloves should never be worn when using insulated live-line tools. If the insulation on the tool is bad the worker would never know it while wearing insulated gloves.This statement also was posed by a 20-year veteran. I

had to think about that a moment. Hmm, would I want to find out the tool is bad by not wearing gloves? Those of you that have ever watched insulation break down when performing high-potential testing will testify that the breakdown happens quickly — faster than you could drop a bad switch stick!

3. We would like to adopt NFPA 70E as our working elec-trical safety policy, but it is entirely too cumbersome.I have advocated NFPA 70E in its forms throughout the

years and do admit in some cases the recommendations may be a bit cumbersome. However, realizing the intent of the publication should shed light on how to implement the appropriate policies. There is not, to my knowledge, a single safety document covering every possible scenario in the electrical industry, nor will there ever be since ours is such a dynamic field. In the absence of specific rules from OSHA, the intent should still be to protect the workforce from hazards. Therefore, a site-specific or activity-specific policy would be appropriate, as long as it meets the intent of protecting the workforce.


I keep a keen eye on the citations and violations of federal and many state OSHA organizations and have yet to see a citation for not following an NFPA 70E recommendation verbatim. NFPA 70E is not an enforceable document — yet. It is a guideline for developing a safe electrical work envi-ronment and has many practical applications the employer could use or modify, if necessary, to meet specific needs. If an employer were to adopt NFPA 70E in its entirety, I am certain it would be following all the OSHA rules.

4. If I were actually to develop a hazard analysis and energized electrical work permit before performing every task, as recommended in NFPA 70E, I would spend all day doing hazard analysis and never get the work done.If you weren’t already doing some form of hazard analysis

before performing electrical work, I would say you should findadifferentoccupation!Therecommendationtoperforma hazard analysis and develop a written energized electrical work permit plan for hazard mitigation applies to those tasks that are not routine in nature (“not routine” being less frequently than annually). The system will not be locked and tagged, and the system will be energized or possibly energized. If the task is performed frequently, an original hazard analysis with successful mitigation techniques should already be in place in one form or another. Thus, another analysis is not required.

Further, NFPA 70E, 2004, Article 130.1(A)(3) Exemp-tions to Work Permit says: “Work performed on or near live parts by qualified persons related to tasks such as testing, troubleshooting, voltage measuring, etc., shall be permitted to be performed without an energized work permit, provided appropriate safe work practices and personal protective equipment in accordance with Chapter 1 are provided and used.” To give an example, a qualified worker should already know the hazards involved in taking current measurements in a motor control center. Would the hazards change from one bucket to another? I would say no. Therefore, the same techniques found to be successful in one application of shock and flash protection would be successful in other similar applications. There is no reason to perform multiple (written) hazard analyses and mitigation procedures for basically the same task.

5. OSHA has a new requirement to perform an arc flash hazard assessment and mark the equipment.No, and no. OSHA has no new mandate to perform a

specific hazard assessment for arc flash. There is an existing requirement to perform a hazard analysis for any hazard an employee may face on the job (see 1910.132(d)(1) in #1 above). That requirement has been in the register for years. What is new is the ability to quantify the existing arc flash hazard. Now that reasonable engineering means are avail-able to quantify the flash hazard, there is more emphasis on ensuring the employees are protected. In the 2002 National Electric Code (NEC) Article 110.16 requires the marking

of flash hazards on equipment wherever the possibility of energized work exists. This is not an OSHA mandate, it is an NEC requirement.

6. I didn’t have to be sitting down to hear the news that there is an arc flash hazard in electrical equipment. I already knew that, so why do we have to put a sign on the equipment?This issue has been a hot topic in the field. I again refer

to the intent of the code, not necessarily the verbatim ap-plication. In the fine print note associated with NEC Article 110.16, it says to refer to NFPA 70E for assistance and then mentions key terms: “determining the severity of the hazard,” “qualified worker,” “appropriate PPE.” I sincerely believe the intent of Article 110.16 is to arm the qualified worker with enough information to make an intelligent choice when selecting the appropriate PPE:

CFR 29 also says, in 1910.335(a)(1)(i), that “Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed.” One of the requirements to be considered qualified to perform electrical work is the ability to identify live versus other components in electrical equipment and to identify operating system voltages.

7. If there were a sign on a piece of equipment that said, “DANGER — VOLTAGE,” would that be sufficient information for a qualified worker to select the appro-priate insulated gloves or tools?I think not. The voltage level is what quantifies the hazard

so the appropriate PPE and tools can be selected. The intent of the arc flash protection program should be the same. Simply putting a sign on a piece of equipment that says, “DANGER—FLASHHAZARD”wouldnotbesufficientinformation for a qualified worker to select the appropri-ate fire-retardant materials or flash protection equipment. The purpose of the training requirement to identify system voltages and live versus other components is twofold: abil-ity to determine when a shock hazard exists and ability to determine level of insulating tools or gloves required. There should also be a training requirement associated with arc flash protection. Never have I seen so many blank stares from supposedly qualified electrical workers as when I show an example of an arc flash warning sign indicating magnitude of hazard at a working distance.

8. That sign says there are 11.4 calories at 18 inches. I ate ten times that many calories for breakfast this morning!This is undoubtedly the most significant training chal-

lenge I have faced in recent years. How do you take a group of electricians or instrument technicians from volts, amperes, and time to calories per square centimeter (or, worse yet, Joules and millimeters) at a given working distance? Don’t blame it on the aptitude of the audience either. I received


much the same response from the audience at an IEEE meeting recently too!

A thorough explanation is needed of the transition from watt-seconds (which most understand) through Joules (which some understand) to calories applied to square centimeters of bare skin (which no one understands). Such an explanation usually results in positive head nods or the “I get it!” looks. Of course, showing the gory electrical burn victim movies helps to drive home the point.

I would hope that those engineers performing incident energy studies will keep in mind the target audience for the results. Providing a report in Joules per millimeter as well as recommendations for flame retardant materials with ratings of calories per square centimeter will only daze the confused. Help them out — provide some training along with the re-sults of the incident energy study correlating study findings with minimum arc thermal performance values and maybe try to explain heat attenuation factor percentages too.

9. I have longer arms than you. Does that mean I can wear different flame retardant clothes?No, because I sweat more than you do…

DavidK.Kregerhasover17years’experiencewithhigh-,medium-,and low-voltage power generation, transmission, and distribution systems. His formaleducation includesaBS inphysics fromNewYorkStateUniversity andanAAfromtheUniversityofMaryland. Hegainedextensive experience as a field engineer through testing, troubleshoot-ing, commissioning, and repairing power systems as well as through high-voltage work as a utility lineman. He is a licensed power engineer, NETALevelIIICertifiedTechnician,memberoftheNFPA(electri-cal section), and master instructor for the training division of Emerson Electrical Reliability Services.


Arc Flash Concerns


by Conrad St. PierreElectric Power Consultants

Arc-flash energy is the latest hazard to receive much-needed attention. While the arc flash hazard has been aroundformanyyears,itwasnotuntil1982thatRalphLeeproposed a method to quantify arc energy. In his paper, an equation defines the “safe” distance a worker can be from an arc without being excessively burned. Any curable burn or one that is not life-threatening he considered accept-able. Severe burns to the chest or head area he considered life-threatening.

Severe arc flash burns can cause a slow, painful death. Hot gases can injure lungs and impair breathing. Even curable burns can result in painful skin and tissue injury that can take weeks to heal. Not all arc flash injuries are physical. Psychologicaleffectssuchasdepression,jobapprehension,and family strife can also be present. Therefore, avoidance of any burn is important in terms of time, money, and a person’s well being.

To improve electrical safety and to inform electrical technicians of the burn hazards of electrical arcs, wording was added to the 2002 National Electrical Code (NEC). The wording can be paraphrased as follows: “Flash protec-tion is required when examining, adjusting, servicing, or maintaining energized equipment. The equipment shall be field-marked to warn qualified persons of potential electric arc flash hazards.”

The 2002 and proposed 2003 revision of NFPA 70E states “Flash hazard analysis shall be done before a person approaches any exposed electrical conductor or circuit part that has not been placed in an electrically safe working condition. The flash hazard analysis shall determine the flash protection boundary and the personal protective equipment that people within the arc flash boundary must use.”

While OHSA does not directly state what to do about arc flash hazard, the wording in OHSA 29 CFR 1910.132(d)(1) requires the employer to conduct and evaluate the work-place for hazards. Based on the employer’s assessment, the employer must select and require the use of appropriate

personal protective equipment (PPE). Since arc flash is a hazard, the above statement could easily be interpreted as requiring some means of quantifying and identifying the hazard to determine the appropriate PPE.

Late in 2001, the IEEEworking group for arc flashhazard was formed to quantify the energy released in an electric arc. Tests were made at voltages between 208 volts to 15 kilovolts. From these tests, empirical equations were developed to estimate the arc energy based on voltage, bolted fault current, distance, system grounding, and type of equipment where the arc is taking place. By the end of 2002, the IEEE Std.1584-2002 was available. This standard provides details of the calculation methods.

While NFPA 70E gives some of the same equations as given in IEEE Std. 1584-2002, more detail is given in the latter. The focus of NFPA 70E and IEEE Std. 1584-2002 is the radiated heat or incident energy falling on a surface produced by an arcing fault. The incident energy generally used as a guide to restrict the flash hazard to a second-de-gree or curable burn is 1.2 calorie/cm2 (1.2 calorie/cm2 = 5.02 Joules/cm2 = 5.02 Watt-sec/cm2). A bolted fault does not produce any radiated flash energy; therefore, any bolted short-circuit current calculation has to be translated to the maximum expected arc energy due to an arcing fault. IEEE Std. 1584-2002 provides the equations to do this. The three documents (NEC, NFPA 70E, and IEEE Std. 1584—2002) should be viewed as a working package for arc hazard ex-posure and personal protection.

Procedure for Arc Flash Hazard Calculations

There are a number of steps in an arc flash calculation. The steps below are based on using IEEE Std. 1584-2002 equations. NFPA 70E also provides equations to determine the arc flash boundaries and energies, but the author be-lieves the IEEE Std. 1584-2002 method is more exact. The steps are:


1.Usingasinglelinediagram,determinethecircuitim-pedances of cables, transformers, bus ducts, and other branch impedances.

2. Add to the network the source impedance of short-cir-cuit contributors such as motors, generators, and utility connection.

3. Solve the network for the bolted short-circuit currents at the buses where electrical equipment exists or where electrical work is to be done.

4. From the bolted current, determine the expected 100 percent arcing current and 85 percent arcing current for the IEEE Std. 1584-2002 equations.

5.Usingtheprotectivedevicesettingoperatingcharacter-istics (curves), determine the total clearing time for the protective device based on the arcing current.

6. Based on the class of equipment [cable, switch-gear, motor control center (MCC)], voltagelevel, and the expected working distance from the energized conductor to the person’s chest or head area, calculate the incident energy (calo-ries/square centimeters) at 100 percent and 85 percent arcing current. Select the higher value. The incident energy equations are in IEEE Std. 1584-2002.

7. Based on the class of equipment (cables, switch-gear, MCC), determine the flash protectionboundary where onset of a second degree burn would occur. This is usually taken at 1.2 Cal/ cm2. The flash boundary equations are in IEEE Std. 1584-2002.

8. Voltage level determines several other distances that may be of interest. These are: • Limitedapproachboundary• Restricted approach boundary• Prohibited approach boundary. These distances are given in NFPA 2002. The

voltage level also gives the voltage-rated PPE (gloves, tools, etc.) that should be used.

Commercial power system software can greatly reduce the burden of finding short-circuit currents, protective-device operating times, and the arc flash calculations. The arc flash calculations can be part of the software package. The IEEE Std. 1584-2002 includes an arc flash calculation spreadsheet that can be used once the short-circuit calculations are made and relaying times are known.

Table 1 and Figure 1 show the information used to cal-culate the incident energy for the diagram shown in Figure 1. If this system did not have a secondary main breaker, the fuse at 4.16 kilovolts would clear the fault on the 480-volt bus. Because of the fuse characteristics, the fault clearing time at 85 percent arcing current is more than twice as long as the time for a 100 percent fault. This increases the pos-

sible incident energy exposure for a person working on the 480-volt bus from 8.8 to 17.6 calories/cm2. The risk hazard category for PPE is three in either case.

Table 1 — Summary of Arc Flash CalculationsLocation 100% Fault

Bolted kA Arcing kA Time (Sec) Cal/cm2

Main 33.7 17.3 0.21 4.4Feeder 48.1 23.2 0.05 1.4Fuse 33.7 at 480V 17.3 at 480V 0.42 8.8

85% FaultMain 33.7 14.3 0.30 5.3

Feeder 48.1 19.7 0.05 1.2Fuse 33.7 at 480V 14.3 at 480V 1.0 17.6

IEEE Equations and Test Results for Open Arcs

The equations given in IEEE Std. 1584-2002 are based on experimental 208-volt to 15.0-kilovolt testing and results. Three sets of equations are provided for voltage ranges of 208 to 1000 volts, 1001 to 15,000 volts, and >15,000 volts. The empirical equations given in the standards for voltages up to 1000 volts tend to give the higher limits of energy

Figure 1 — Curve to Determine Protective Device Operating Times


radiated from the test arcs. The actual radiated energy could be higher than the values given from the equations. The environment in which thearctakesplaceaffectsthearc.Factorssuchashumidity, power factor, contaminants, tempera-ture, enclosure, length of an arc, impedance of an arc, duration of an arc, and material consumed inthearcwillaffecttheradiatedenergy.

Figure 2 shows the plot of the developed equations given in the IEEE Std. 1584-2002 reference to the test data for 600-volt tests for an open-air arc. An open arc is one where heat is radiated in all directions. A fault on a cable in an open tray could be considered an open-air arc. The calories/square centimeter incident energies in this figure are based on a surface located 24 inches (61 centimeters) away from the arc and for a 1.0 second fault duration. The curve labeled “IEEE 1584 Equations” is derived from IEEE Std. 1584-2002 Equations 1 to 6 for an arc gap of 1.25 inches (32 centimeters). IEEE Std. 1584-2002 also provides an equation based onRalphLee’smethod.This equationis used for voltages greater than 15 kilovolts until future tests are done at higher voltages. Thecurvelabeled‘IEEELee’sMethod’isfroman equationbasedon an adjustment toLee’swork. It is shown for comparison with the IEEE Std. 1584-2002equationsandtestdata.Lee’smethod is simpler and more conservative, since it calculates the incident energy without know-ing the arc gap or the arcing current. The IEEE Std. 1584-2002 equations calculate an estimated arc current from the bolted fault current and arc spacing. These values are then used to calculate the incident energy. At 600 volts, IEEE Std. 1584-2002equationsandIEEELee’sMethodequation follows the higher incident energy test values.

Figures 3 and 4 show the relationship of the IEEE Std. 1584-2002equationsandIEEELee’smethod equations to the test data. In this case, some of the test data points are significantly above the IEEE Std. 1584-2002 equations. In the calculations of incident energy for systems greater than 1000 volts, the study engineer may desire to increase the calculated values by a factor of 2.0 to insure a safety margin or change Cf (in IEEE Std. 1584-2002 Equation 6) to 2.0 for voltages greater than 1000 volts.

While using the methods in NFPA 70E or IEEE Std. 1584-2002 does not insure that burns from an arc flash will not injure a worker, it indicates that the worker has taken steps to reduce the risk of injury. Following the NFPA 70E procedures and wearing the proper protective equipment willgreatlyreducethepossibilityofburns.Usingtheinci-dent energy equations, it is expected that the PPE per the tables in NFPA 70E will be adequate for 95 percent of the test results used to develop the equations.

Enclosed ArcsMuchoftheworkaroundenergizedequipmentisofthe

metal, enclosed type. The energized conductors are normally enclosed behind removable panels or doors. An arc in these areas is considered “in a box” or “in an enclosure” and will be more intense and directed. The “in an enclosure” measure-ments made by the IEEE Std. 1584-2002 working group gave incident energy intensity two to four times higher than arcs in open air. The equations given in IEEE Std. 1584-2002 have constants accounting for fault in enclosures based on MCCorswitchgearsizecubicles.

Figure 2 — Comparison of IEEE Equations to 600-Volt Open-Air Arc Test Data(IEEE 1584 Equations, based on 24 Inch to Subject, 1.25 Inch Arc Gap, 1.0 Second Exposure)

Figure 3 — Comparison of IEEE Equations to 4160-Volt Open-Air Arc Test Data (IEEE 1584 Equations, based on 24 Inch to Subject, 4.0 Inch Arc Gap, 1.0 Second Exposure)


Figure 4 — Comparison of IEEE Equations to 13,800-Volt Open-Air Arc Test Data(IEEE 1584 Equations, based on 24 Inch to Subject, 6.0 Inch Arc Gap, 1.0 Second Exposure)

Table 2 - Minimum Thermal Protection Recommended

(Based on proposed updates to NFPA 70E)

Flash Hazard Risk Category

Range of Calculated incident energy

Min. PPE Rating Clothing Required

0 0-1.2 cal/cm2 N/A 4.5-14.0 oz/yd2 untreated cotton

1 1.2+ to 4 cal/cm2 4 cal/cm2 FR shirt and pants2 4+ to 8 cal/cm2 8 cal/cm2 Cotton underclothing plus FR

shirt and pants3 8+ to 25 cal/cm2 25 cal/cm2 Cotton underclothing plus

FR shirt, pants, overalls or equivalent

4 25+ to 40 cal/cm2 40 cal/cm2 Cotton underclothing plus FR shirt, pants, plus double layer switching coat and pants or

equiv.5 40+ to 100 cal/cm2 100 cal/cm2 Cotton underclothing plus FR

shirt, pants, plus multi-layer switching suit or equivalent

FR = Fire resistance fabric

Personal Protective Equipment The purpose of these calculations is to determine which

PPE limits the possible thermal energy exposure to the critical body parts such as face and chest areas.Usuallythe calculations give the possible heat exposure level in calories/square centimeters or Joules/square centimeters. Knowing theheat exposure level, the desired protective

clothing can be chosen. Table 2, based on NFPA 70E data, providesthiscross-reference.Glovesratedforthevoltageclass, insulated tools, and face shields will be required for some work tasks around energized equipment. NFPA 70E provides guidelines forPPE required for differentworktasks. Burns from energy levels less than 1.2 calories/cm2 are curable for most persons.


Arc Blast Pressure Another item associated with an electric arc is the blast

energy, or pressure, which is not presently covered in NFPA 70E or IEEE Std. 1584-2002. This force can be significant and can blow workers away from the arc, causing falls and injuries that may be more severe than the burns. In Ralph Lee’s1987paper,hesitesseveralcasehistories.Inonecase,with approximately 100-kiloampere fault level on a 480-volt system, an electrician was somersaulted 25 feet away from the arc. Being forced away from the arc reduces the electrician’s exposure to heat radiation and molten copper, but can subject him or her to falls or impact injuries. The approximate initial impulse force at 24 inches for a 100-kiloampere bolted fault (approximately 42 kiloampere arc) was calculated to be approximately 260 pounds per square foot, as determined from the equation below:

Pounds/Ft2 = 11.5*kA arc (Distance from arc in feet)0.9

Limiting Arc ExposureIncident energy increases with time and fault current.

Reducing either or both lowers the incident energy due to an arcing fault. Incident energy can be reduced by system design or operating procedures. It is best to work on de-energized equipment, but this may not be possible. The following are some means of reducing incident energy:

1. On new or retrofitted breakers with electric close and trip control, place the close/open control switch on a remote or nonbreaker panel.

2. If possible, use a remote or longer operating arm when racking in or opening/closing breakers.

3. Place a barrier between the technician and the device being placed in service or racked in.

4. Review protective devices to see if they can be lowered in time and pickup.

5. When working with double-ended load centers or substations with a normally closed tie, open an incoming breaker or the tie breaker to reduce the fault level.

6. Review protective fuse sizes. Smaller fus-es reduce the exposure time. This can be significant when the arcing current or 85 percent of arcing current is not in the cur-rent limiting range.

7. Change relay settings when working on equipment. For many load centers, both high and low voltages, the feeders have instantaneous protective devices that op-erate and clear the fault in one to eight

cycles, thereby reducing the exposure time. The incom-ing main breaker, in order to be time-coordinated with the feeders, generally will not have an instantaneous en-abled on the protective device. The fault clearing time could be in the range of 0.2 to 1.0 second. This long time greatly increases the arc exposure time and amount of radiation a worker would receive if the arc blast pres-sure were not enough to propel the worker away from the fault.

To limit the arc exposure on buses where the protective devices are time-coordinated, the main breaker shown in Figure 5 could be ordered with an instantaneous pro-tective device and a safety switch. Normally the instan-taneous protection would not be functional due to the open contact of the safety switch. However, when work is being done on the energized equipment, the safety switch would be turned “ON,” thus limiting the arc ex-posure to the worker should an arcing fault accident oc-cur. The time-selective system would be eliminated for duration of the work in the interest of safety.

Electronic-trip low-voltage breakers could have either their short-time or instantaneous pickup setting low-ered when work is being done on the equipment. Some manufacturers have a disable function on the low-volt-age instantaneous adjustment which would be useful on incoming main breakers. The instantaneous adjustment would be disabled for a selective system under normal operation and placed in service for reduced arc-fault ex-posure when working on the equipment.

8. While not a way to reduce arc incident energy, it is good practice to use a buddy system. In the event some inci-dent should happen, help can be summoned quickly if a second person is around.

Figure 5 — Schematic to Control Arc Exposure on Relayed Breakers


Calculation MeansThe calculations for arc flash incident energies and

boundary distances can be accomplished a number of ways. The reader can use the equations in IEEE Std. 1584-2002 after obtaining the bolted three-phase, short-circuit cur-rentandclearingtimes.IEEEalsohasmadeanEXCEL® spreadsheet program available with these equations for approximately $500. The user enters the fault level, voltage, clearing time, and distance from an expected arc to the worker. The program then provides the incident energy and boundary distance. The user would use this data to make the labels to be placed on the electrical equipment. Software companies providing industrial-based electrical system analysis have arc flash hazard packages integrated with their short-circuit and protective device packages.

ReferencesIEEE Std. 1584-2002, IEEE Guide for Performing Arc

Flash Hazard Calculations,NewYork,NY,2002.

Lee,R,“TheOtherElectricalHazard:ElectricArcBlastBurns,” IEEE Transactions on Industry Applications, Vol. 1A-18, No. 3,May/June1982.

Lee,R.,“PressuresDevelopedbyArcs,”IEEE Transactions on Industry Applications, Vol. 1A-23, No. 4, July/August 1987.

National Electrical Code, Article 110.16, 2002, National FireProtectionAssociation,Quincy,MA,2002.

NFPA 70E Standard for Electrical Safety Requirements for Employee Workplaces, National Fire Protection Associa-tion,Quincy,MA,1995.

OSHA 29 CFR 1910.132(d)(1), Occupational Safety and HealthStandardsforGeneralIndustry,Part1910,U.S.DepartmentofLabor,OccupationalSafetyandHealthAdministration.

Copies of the NEC, NFPA 70E, and IEEE Std. 1584-2002 references can be purchased from their parent standard organization.

ConradSt.PierreisagraduateoftheUniversityofMainewithaBSin electrical engineering and a certificate in power system engineering. He receivedaMSfromUnionCollegeinSchenectady,NewYork.PriortoformingElectricPowerConsultantsin1997,hewasemployedbyGeneralElectric and Industrial Power Systems. He has been a member of IEEE and of several subcommittees and served as Chair of the Violet Book working group, dealing with short-circuit calculations. He is a member of theIEEE-1584ArcFlashworkinggroup.HewasamemberoftheUSNational Committee of the International Electrotechnical Commission TechnicalAdvisoryGroupforTC73/WG1andWG2concerningshort-

circuit currents and calculation methods. In 2001, he finished a book, A Practical Guide to Short-Circuit Calculations. Electric Power Consultants, LLC,providesanalyticalengineeringservicestohisclientsandtoclientsofGE,ABB,PTI,HansonEngineers,andANNA,Inc.


Six Steps to Arc Flash Nirvana


by Jim WhiteShermco Industries

Figure 1

Nonfatal electrical accidents involing days away from work, 1992-2001

IndustryIndustry

Finance, insurance, andreal estate

Retail trade

Construction

Mining

Agriculture

Wholesale trade

Transportation andpublic utilities

Manufacturing

Electric shockElectric burns

N = 44,363Electric shock = 27,262Electric burns = 17,101

0 2,000 4,000 6,000 8,000 10,000 12,000

169

795

2,2165,282

6,579

1,895

1,078

5,056

296

212

5,884

478

5,990

3,513

2,324

992

1,012

60

No. of accidents

Source BLS.SOIISome data not meeting BLS publication criteria may not be shown.Data may not sum to totals

In the electrical industry the phrase “arc flash” is gen-eratinga lotof interest.Manymanagersandsupervisorsareasking“Why?”Moretothepoint,manyaresaying,“Idon’tseehowthisaffectsmeormypeople.Wehaveneverhad an arc flash incident.” If this is true, then what is all the fuss about?

Statistically SpeakingAt the 11th Annual IEEE-IAS Electrical Safety Work-

shop, Cawley and Homce of the Center for Disease Control (CDC)/National Institute of Safety and Health (NIOSH) presented statistics showing that during the period from 1992 through 2001 there were 44,363 electrically-related injuries. The number of nonfatal electrical shock injuries was 27,262, and 17, 101 injuries were caused by electric arc flash burn. Figure 1 is one of the slides presented during that presentation. In statistics presented at the 3rd International Conference on Electrical Injury in 1998, the Electric Power

Research Institute estimated the direct costs of an electrical fatality at $1.3 million dollars, with total direct and indirect costs reaching between four and ten million dollars.

Serious electrical injuries can be even more devastat-ing to the people involved as well as to the bottom line. Floyd estimated the total of direct and indirect costs of a major electrical accident at $17.4 million in 2003 dollars. Usingtheaboveestimatesofcostsrelatedtoanelectricalinjuryordeath,thesumcanhaveaveryseriouseffectonacompany’s ability to function. There are also the additional costs for trained personnel to be away from the job recover-ing from an electrical accident: lost production, increases in workman’s compensation and insurance rates, possible OSHA fines, legal fees — the list goes on and on. This does nottakeintoaccountthepain,sufferingandemotionalcostswhich cannot be measured.

Another fact brought out by the CDC/NIOSH study is that electrical burn injuries cause a longer stay away from the job site. (See Figure 2.) Note that, even though burns ac-counted for only 38 percent of the total injuries, they caused a disproportionate number of days lost from work.

If we try to match the figures given in the CDC/NIOSH studywiththoseintheBureauofLaborStatistics(BLS)website,wewillfindthatwecannot.Manyofthenumbersquoted by the CDC/NIOSH study are not available to the general public, so the numbers used do not match up with numberspostedontheBLSwebsite.

TheBLSsiteissomewhatlimitedinthedatasortingitcan do, whereas CDC/NIOSH has access to the complete database. Other important facts in that study:

• In the electrical construction industry, 80 percent of electrical injury victims are electrical workers, not la-borers or helpers.

• Small companies (fewer than 10 employees) had a dis-proportionate number of electrical injuries. Figure 3 il-lustrates company size vs. percent injury.


• Mostinjuriesoccurmorethansixhoursintotheworkshift.

By spending a small amount of time to research this data ontheBLSwebsite,managementcanbegintodeterminehow their company matches up with general industry as a whole and with others in the same industry. Rates per 10,000 workers are also available on the site and may be easier to compare.

shall use.” So, Step 1 on the list is to determine if the work being done is within the FPB.

The FPB can be calculated using the equations given in 70E or by using one of many available software programs, both freeware and commercial. Cooper-Bussmann has a calculator imbedded in its website that will do the job and is free, although calculations must be performed on the website.

In many cases, especially where the available short-circuit current is 10,000 amperes or less, the FPB may only be a few inches. Some examples of low-energy FPBs (all using 9,600-ampere available short-circuit current and protected by a molded-case circuit breaker) are shown as follows:

• 480 volts — three-phase 7.1 inches• 277 volts — single-phase 4.1 inches• 208 volts — three-phase 4.7 inches• 120 volts — single-phase 2.7 inches

In these instances, correct PPE would be voltage-rated gloves and protectors, safety glasses or goggles, 12 ounces per square yard cotton or flame retardant clothing, and safety shoes. The key in these examples is that the avail-able short-circuit current is less than 10,000 amperes. If a circuitisfedbyanAWG12orlesswireandissuppliedbya general-purpose circuit breaker or fuse (10,000-ampere interrupting rating), it would match the above figures. If the short-circuit available current is higher, the FPB will increaseaswell.MorePPEwouldbe required tomatchthe hazard.

Step 2: Gather the InformationThe next step is to gather the information needed to

perform the calculations. Several pieces of information are required, including:

• Available short-circuit current at the point of fault• Nominal voltage• Maximumtotalclearingtimeoftheprotectivedevices• Working distance• Type of ground system being used• Type of protective device (including model numbers

and settings)

This is the same information that is derived from the short-circuit analysis and coordination study. It is important that this information is correct and up-to-date or subsequent steps will be pointless.

Step 3: Perform an Arc Flash StudyThis third step calculates the incident energy that would

be received by the worker at the point of contact. The IEEE Guide1584-2002canbeusedtodeterminetheFPB,theincident energy at working distance, and the PPE required. It is used as a plug-in for many of the available engineering

Figure 2

Median days away for electrical shock and burn injuries,all industries, 1992-2001

25

ShocksBurns

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

20

15

10

5

0

Year

Day

s

Source: BLS. SOII

Figure 3

Company size of electrical victims employed by electrical contractors,1992-2000

50%

N = 359

1 to 10 11 to 19 20 to 49 50 to 99 100+ Not reported

40%

30%

20%

10%

0%

Company size (no. of employees)

Perc

ent

Source: BLS. CFOI

Only cases reporting establishment size, SIC, and nature of injury are shown

39%

9%

14%10%

18%

10%

Step 1: Determine the Flash Protection Boundary and Personal Protective Equipment

Now that the need has been established, what does a company need to do? In the area of arc flash protection, the first thing is to determine if a danger exists. NFPA 70E, “Standard for Electrical Safety in the Workplace,” states in Article 130.3, “A flash hazard analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. The analysis shall determine the Flash Protec-tion Boundary (FPB) and the personal protective equipment [PPE]thatpeoplewithintheFlashProtectionBoundary


software packages on the market. The incident energy provided by the spreadsheet calcula-

tor will be given in calories per square centimeter and needs to be reviewed to determine if adequate PPE is available and must be documented.

Figure4showsascreenshotoftheSKMsoftwarepack-age used by Shermco Industries when performing arc flash studies. The FPB, working distance, and incident energy are all detailed. Also given is the NFPA Hazard Risk Category (HRC) required for the worker. If the incident energy is too great, it is flagged and highlighted on the spreadsheet.

One of the issues that arises when performing these calculations is that of the working distance. IEEE 1584 provides recommended working distance for use in its cal-culations, but in real life people are not so precise. A change ofjustafewinchescanmakeatremendousdifferenceintheincident energy received by the worker. Often, increasing the distance by six inches from the component or part to the worker reduces the incident energy 30 percent or more. This cannot be applied in many situations but can be for tasks such as racking circuit breakers in and out of their cubicle. Longerrackinghandlesorremoterackingdevicescanbeused to decrease incident energy to a tolerable level.

Step 4: Choose the Correct PPECorrect PPE selection is critical to protecting the worker.

After performing the incident energy calculations, the de-rived calories per square centimeter must be compared with the PPE being considered. Prior to the year 2000, there were no markings on flash protective equipment to show its arc rating. After that date the NFPA 70E required that PPE used as arc flash protection be marked with the arc rating in caloriespersquarecentimeteronthelabel.Unfortunately,70E did not specify that the face shield material be rated

for the same heat as the rest of the PPE, and some low-dollar providers of PPE sold substandard face shields. This was resolved in the 2004 revision of 70E which requires that the face shield provide the same arc rating as the rest of the flash protection.

According to NFPA 70E, incident energy received by the worker must be reduced to no more than 1.2 cal/cm2. As an example, holding one’s finger over a match for one second produces an incident energy of 1.0 cal/cm2, while 1.2 cal/cm2 is considered to be the amount of heat required to produce onset of a second-degree burn on unprotected skin. Even though the worker wears arc flash protective equip-ment, he can still receive burns if the heat is high enough. The heat passing through the PPE can be high enough to melt the elastic in undergarments. A good rule-of-thumb is to use PPE with an arc rating equal to or greater than the calculated incident energy.

Step 5: Mark the EquipmentThe 2002 revision of NFPA 70, commonly known as the

National Electrical Code, requires that new equipment be field-marked to warn of the hazards if the cover is removed. This is stated in Article 110.16:

“Flash Protection. Switchboards, panelboards, and motor control centers in other than dwelling occupan-cies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

Figure 4

Bus Name Protective Bus Bus Prot Dev Prot Dev Trip/ Breaker Ground Equip Gap Arc Flash Working Incident Required Protective

Device kV Bolted Bolted Arcing Delay Opening Type Boundary Distance Energy FR Clothing Class

Name Fault Fault Fault Time Time (in) (in) (cal/cm2)

(kA) (kA) (kA) (sec.) (sec.)

11USS13.8kV LD 11USS HVFU 13.8 18.08 17.91 17.21 0.01 0 No SWG 153 9 36 0.30 Class 0

11USS13.8kV LN SR750 11USS 13.8 18.08 17.91 17.21 0.016 0.083 No SWG 153 92 36 2.97 Class 1

12USS13.8kV LD 12USS HVFU 13.8 22.79 21.55 17.53 0.08 0 No SWG 153 80 36 2.60 Class 1 (*3)

12USS13.8kV LN SR750 12USS 13.8 22.79 21.55 20.63 0.02 0.083 No SWG 153 122 36 3.91 Class 1

13USS 103B LD 13USS 103B 0.48 60.56 57.65 26.87 0.05 0 No SWG 32 56 24 4.20 Class 2

13USS 103C LD 13USS 103C 0.48 60.56 57.65 26.87 0.05 0 No SWG 32 56 24 4.20 Class 2

13USS 103D LD 13USS 103D 0.48 60.56 57.65 26.87 0.05 0 No SWG 32 56 24 4.20 Class 2

13USS 104B LD 13USS 104B 0.48 60.56 57.65 26.87 0.05 0 No SWG 32 56 24 4.20 Class 2

13USS 104C LD 13USS 104C 0.48 60.56 57.65 26.87 0.05 0 No SWG 32 56 24 4.20 Class 2

13USS 13.8kVLD 13USS HVFU 13.8 19.25 18.86 18.1 0.01 0 No SWG 153 9 36 0.32 Class 0

13USS 13.8kVLN SR750 13USS 13.8 19.25 18.86 18.1 0.016 0.083 No SWG 153 97 36 3.15 Class 1

13USS 480V BUS 13USS MAIN 0.48 60.56 45.99 18.22 0.652 0 No SWG 32 246 24 36.8 Class 4 (*3)

13USS MAIN LN 13USS HVFU 0.48 60.56 45.99 21.44 2 0 No SWG 32 583 24 131 Dangerous!!!


FPN No. 1: NFPA 70E-2000, Electrical Safety Requirements for Employee Workplaces, provides as-sistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

FPN No. 2: ANSI Z535.4-1998, Product Safety SignsandLabels,providesguidelinesforthedesignofsafety signs and labels for application to products.”

This applies to all equipment installed after January, 2002. Why should any company worry about labeling? OSHA has amultiemployerworksitepolicy(CPL2-0.124)thatmakesit clear that the equipment owner is just as responsible for contractor safety as the contractor is. If a company allows the contractor on its job site, that company has approved the contractor’s safety procedures and policies. Because of this, the smart move for any company is to be proactive, especially where known hazards exist. Employees as well as contracted workers can not always be counted on to know themethods and reasons of arc flash protection.Manyworkers lack the training and knowledge needed to choose therightPPEaccurately.Labelingtheequipmentensuresthat those who work on power system equipment will be aware of the shock and arc flash hazard involved and the required flash protective equipment. An example label is shown in Figure 5.

Step 6: Train the WorkersOSHA and NFPA 70E require that workers be qualified

in order to work on or near energized electrical systems. “Qualified”isdefinedin29CFR1910.399as“onewhoisfa-miliar with the construction and operation of the equipment and the hazards involved.” Further, 29CFR1910.331(a) states, “The provisions of 1910.331 through 1910.335 cover electrical safety-related work practices for both qualified persons (those who have training in avoiding the electrical hazards of working on or near exposed energized parts) and unqualified persons (those with little or no such training) working on, near, or with the following installations:” [a listoffacilitiesisthengiven].Thisstatementrequiresthatqualified workers also be trained in how to avoid the hazards. 29CFR1910.269 has similar requirements for those working on systems rated above 600 volts.

Inorderforthearcflashstudytobeeffective,workersmust be trained in what the labels mean and how to apply the information on them. One of the first things OSHA does during a site inspection or an accident investigation istoreviewthetrainingrecordsforthatcompany.Lackoftraining is often cited as a reason for large fines that come soon afterward. Who needs training? Almost everyone needs training.Unqualifiedworkersmust be trained onthehazardsofelectricityandhowtoavoidthem.Qualifiedworkers must meet the above requirements and other spe-cific requirements given in 29CFR1910.332 and -.269.

Manycompaniesprovidingon-the-job(OJT)trainingdoa poor job of documenting that training. OSHA will accept OJT, but if a company doesn’t document it, it may as well never have happened. Documentation includes date, name of attendee, and topic covered as well as initials or signature of attendee verifying he actually took the OJT.

NFPA 70ENFPA 70E has been mentioned a number of times in this

paper. It is important for companies to have a copy of this document. In 1979, OSHA asked the NFPA to develop a consensus standard they could use to write the regulations. OSHA has two nonvoting members on the 70E Com-mittee to ensure it stays consistent with the regulations. In fact, NFPA is conducting seminars for OSHA Compliance Officers on how to use 70E when writing citations. OSHA has used 70E as justification for these citations in court, and the court has upheld that practice.

One of the best features of 70E is the set of tables labeled “Table 130.7.” These tables are helpful in choosing what PPE would be required for standard tasks performed by electrical workers. Figure 6 shows a partial view of Table 130.7(C)(9)(a), “Hazard/Risk Category Classifications.” Each general type of equipment is grouped and common tasks are listed. Each task is assigned a Hazard/Risk Cat-egory number (HRC) from HRC0 to HRC4, with HRC4 being the highest. For example, “insertion or removal (racking) of CBs from cubicles, doors closed” (on 600V Switchgear) shows an HRC 2, while the same action with open doors rates an HRC3. It is critical that the notes at the

Figure 5


Figure 6

Figure 7


bottom of each table be reviewed and understood. The tables cannot be used outside of the stated limitations; otherwise, injury or death could result.

Table 130.7(C)(10) in Figure 8 shows a partial list of PPE required for the various HRCs. This would be used in conjunction with Table 130.7(C)(11), “Protective Clothing Characteristics” shown in Figure 9.

A change has been made to 70E Table 130.7(C)(9)(a), even though the standard has only been out since April of this year. Some of the notes at the bottom of the table have been revised as follows:

Note Number Changes Made (In Italics)

1 Maximum of 25-kiloampere short-circuit current avail-able, 0.03 second (two-cycle) fault clearing time.

2 Maximum of 65-kiloampere short-circuit current avail-able, 0.03 second (two-cycle) fault clearing time.

4 Maximum of 42-kiloampere (from 65-kiloampere) short-circuit current available, 0.33 second (20-cycle) fault clearing time.

5 Maximum of 35-kiloampere (from 65-kiloampere) short-circuit current available, up to 0.5 second (from 1.0 second) (30-cycle) (60-cycle) fault clearing time.

Corresponding changes were made within the table to reflect the changes in the notes.

SummaryAn electrical accident can have far-reaching and severe

negativeaftereffects.Asmuchasanythingelse,thelitiga-tion that will follow diverts needed resources and hurts morale.Mostcompaniesarealreadypressedformanpowerand time. Adding the burden of an arc flash study, coupled with the time and expertise involved in performing it, can beadauntingtask.Manycompaniesofferarcflashstudiesand will handle everything from calculations to marking equipment to training.

One last thought on this topic: electrical equipment maintenance. All ratings and calculations are performed with the expectation that protective devices will function correctly, are correctly coordinated, and are set to that co-ordination study. Our experience has been that this often is not the case. In nearly every facility in which we work, there are breakers and switches that are too slow or non-functional due to lack of maintenance. This may increase the time of exposure to an arc from four to six cycles to one to three seconds, or even longer if the next upstream deviceisrequiredtoclearthefault.Underthesecircum-stances, there is no protective equipment that could protect a worker. Adequate maintenance is as critical to safety as the selection of PPE.

References1. ANSI/NFPA 70, National Electrical Code, 2002.

2. ANSI/NFPA 70E, “Standard for Electrical Safety in the Workplace,” April, 2004.

3.BureauofLaborStatisticswebsite,www.bls.gov.

4.Cawley, James, PE and Homce, GeraldT., “Occupa-tionalElectricalInjuriesintheUnitedStatesandRec-ommendations for Safety Research,” Journal of Safety Research 34, 2003, pp. 241—248, 11th Annual IEEE Electrical Safety Workshop.

5. Electric Power Research Institute, 3rd International Conference on Electrical Injury. 1998.

6.Floyd,H.Landis,“FactsonElectricalIncidentandIn-jury Costs,” 11th Annual IEEE Electrical Safety Work-shop.

7.IEEE 1584-2002, “Guide for Performing Arc FlashCalculations.” October, 2002.

8. OSHA 29CFR1910.331 - .335, Subpart S, “Electrical Safety-Related Work Practices.”

9. OSHA 29CFR1910.269, Subpart R, “Electric Power Generation,TransmissionandDistribution.”

Jim White is currently the Training Director for Shermco Industries, a NETA Accredited Company. Jim represents NETA on the NFPA’s 70E CommitteeastheAlternateandisaLevelIVcertifiedtechnician.Jimhas spent the last twenty years directly involved in technical skills and safety training for electrical power system technicians.


Arc Flash Hazards to Be StudiedNETA World, Winter 2004-2005 Issue

by Ron Widup and Jim WhiteShermco Industries

The IEEE and NFPA have announced formation of a newArcFlashHazardWorkGroup(9/13/04).Thisworkgroup is to review existing information relating to the thermaleffectsofanarcandprovideaccurateandverifiabledata. In addition, this work group, unlike the IEEE P1584 work group, will consider other hazards created by a fault, includingpressurewave(arcblast)andacousticeffects.TheIEEE/NFPA Steering Committee established a Research and Test Planning Committee (RTPC) to develop a re-search and test plan that will provide data on the nature of electrical arcs. The objectives of the committee are:1. Develop a research and test plan to predict the various

forms of energy to which a person might be exposed during an arc.

2. Verify existing protocols or generate new protocols to measuretheeffectsofanarc.

3. Develop a scientific relationship between electrical characteristics and hazard characteristics of an arc to develop directly usable data.

4. Define the mechanisms of thermal energy transfer from an arc to the surrounding area and the relationship of each to potential injury.

5. Provide adequate and scientifically verifiable data to the IEEE and NFPA standards and code processes to enable thedevelopmentofeffective safeguards forarcflash hazards.

6. Develop a testing process to determine the intensity of ultraviolet, infrared, x-ray, and any other potentially in-jurious energy bands emitted during an arc as well as to determine the potential for injury from each.

7. Determine the impact of equipment installed within an enclosure on existing data related to an arc-in-the-box or develop new information.

As the test parameters and instrumentation (to be defined by the RTPC) are defined, the RTPC will give special consideration to the following factors:

• Locationofthearcwithintheequipment• Orientationofthearcwithintheequipment• Capacityoftheelectricalsystem• Protectivedevicesandcomponentsnormallyprovided

in a system• Electricalequipmentnormallyfoundinthefield

NETA is a contributor for this project, and Jim White (Shermco Industries) is NETA’s representative on the work group. NETA is always looking for ways to further safe working conditions for member companies and their employees and has representatives on the NFPA 70E Com-mittee as well as various NFPA, NEC, IEEE, and ANSI committees.

The hazard of pressure waves created by electrical arcs is one that has not been fully investigated. While fewer injuries and fatalities from the pressure wave are believed to occur than from the hazard of shock or arc flash, once this pressure wave hazard is studied and quantified in the samemanner as the thermal effectsof anarc,protectivemeasures for the pressure wave can be established. Either new personal protective equipment can be developed or existing personal protective equipment can be shown to be adequate for this hazard.

At a presentation given at the 11th Annual IEEE/IAS Electrical Safety Workshop, it was stated that projectiles from exploding electrical equipment can reach speeds of 700 miles per hour. The result of being hit by such an object, plus other hazards such as molten metal and arc plasma vapor, can cause serious injury or death. The study and analysis of this hazard phenomenon are crucial for the continuous improvement of a safer work place.

We will keep you updated as the information develops. Be safe.

Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). Ron is past president of NETA and currently a member of the Board of Directors and Standards Review Council. Both are employees of Shermco Industries.


Dennis K. Neitzel, C.P.E.AVO Training Institute, Inc

PowerTest 2005(NETA Annual Technical Conference)

Electrical Hazards Analysis

Pr ohibi ted Ap pr oach B oundar y

Re str icted Appr oac h B oundar y

Li mited Appr oach B oundar y

Cr itical point or I nitia tion of a rc

Flash Pr otection B oundar y

IntroductionThe subject of electrical hazards analysis has been recog-

nized by a small segment of the electrical industry for many years. The petrochemical industry and many government institutions have performed research on this subject for over twenty years. For the most part however, the electrical industry, at least at the user level, has largely ignored the subject, essentially reacting to catastrophic accidents, rather than proactively trying to predict and prevent them. Recent changes in consensus standards, along with a better general understanding of the seriousness of electrical hazards have resulted in a renewal of interest in the subject.

As the awareness of electrical hazards increases many arepuzzledbyphraseslike;“LimitedApproachBoundary,”“Restricted Approach Boundary,” “Prohibited Approach Boundary,”and“FlashProtectionBoundary.”Understand-ing these terms is important to understanding shock and arc flash hazard protection. Below are the definitions of these termsasfoundinNFPA70E-2004,Article100:[1]

LimitedApproachBoundary- “An approach limit at a distance from an exposed live part within which a shock hazard exists.”

Restricted Approach Boundary- “An approach limit at a distance from an exposed live part within which there is an increased risk of shock, due to electric arc over combined with inadvertent movement, for personnel working in close proximity to the live part.”

Prohibited Approach Boundary- “An approach limit at a distance from an exposed live part within which work is con-sidered the same as making contact with the live parts.”

Flash Protection Boundary- “An approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur.”

Illustration of Boundaries

The NFPA 70E-2004, “Standard for Electrical Safety in the Workplace”, addresses the requirements for conduct-ing an “Electrical Hazard Analysis” with emphasis on the “Shock Hazard Analysis” and the “Flash Hazard Analysis”. NFPA 70E-2004 tells us that if circuits, operating at 50 volts or more, are not deenergized (placed in an electrically safe work condition) then other electrical safety-related work practices must be used. These work practices must protect the employee from an arc flash, as well as inadvertent contact with live parts operating at 50 volts or more. These analyses must be performed before an employee approaches exposed liveparts,withintheLimitedApproachBoundary.

This paper will provide an overview of the principle types of electrical hazards analysis, along with a discussion of the relevant standards and regulations pertaining to the subject.

Shock Hazard AnalysisEach year several hundred workers are injured or killed

due to inadvertent contact with energized conductors. Surprisingly, over half of those killed are not in tradition electrical fields (i.e. linemen, electricians, technicians, etc.), but are from related fields such as painters, laborers, and drivers. [Detailed surveillance data and investigative reports


of fatal incidents involving workers who contacted ener-gized electrical conductors or equipment are derived from the National Traumatic Occupational Fatalities (NTOF) surveillance system maintained by the National Institute forOccupationalSafetyandHealth(NIOSH)].Becauseof this, NFPA 70E-2004 established a new requirement for conducting a “Shock Hazard Analysis” in order to deter-mine the voltage that a person would be exposed to, shock protection boundaries, and personal protective equipment requirements.

Investigations into the causes of injuries and fatalities pointtoseveralcontributingfactors[2]:• Faulty insulation;• Improper grounding;• Looseconnections;• Defective parts;• Groundfaultsinequipment;• Unguardedliveparts;• Failure to deenergize electrical equipment when it is

being repaired or inspected;• Intentional use of obviously defective and unsafe tools;

or• Useoftoolsorequipmenttooclosetoenergizedparts.

These factors form the basis for a shock hazard analysis.

To appropriately assess the electrical shock hazard as-sociated with any type of maintenance or repair work, it is necessary to evaluate the procedures or work practices that will be involved. These practices should be evaluated against both regulatory and consensus standards requirements as well as recognized good practice within the industry. These principles are summarized below.

OSHA Regulatory Requirements• All equipment must be placed in a deenergized state

prior to any maintenance or repair work. (limited excep-tionsexist).[3][4]

• The deenergized state must be verified by a qualified personpriortobeginninganywork.[3]

• The deenergized state must be maintained through the consistent use of locks and tags, and in some cases, grounding.[3][4][5]

• When energized work is performed, it must be per-formedinaccordancewithwrittenprocedures.[3][6]

NFPA 70E-2004 Standard Requirements [1]• The Shock Hazard Analysis must establish the:1. LimitedApproachBoundary2. Restricted Approach Boundary3. Prohibited Approach Boundary• This applies to all exposed live parts operating at 50

volts or more

• Only qualified persons are permitted within these boundaries.

• Unqualifiedpersonmaynotentertheseboundariesun-less the conductors and equipment have been placed in an electrically safe work condition.

Industry Recognized Good Practices• Plan every job.• Anticipate unexpected results and the required action

for these results.• Useproceduresastools.• Identify the hazards. Keep unqualified workers away

from these hazards.• Assessemployee’sabilities.Remember,thereisadiffer-

ence between ten years of experience, and one year of experience repeated ten times.

In addition to the assessment of work practices, the shock hazard analysis must include an assessment of the physical condition of the electrical system. The assessment must also identify the proper PPE for shock protection, which would include, but not be limited to, rubber insulating gloves with leather protectors, rubber blankets and mats, and insulated hand tools.

Insulated Tools and Rubber Insulating Gloves

Another consideration is the continuity and low resis-tance of the equipment grounding system, which is a major concern. Of equal importance is to insure that equipment covers and guards are in place; that access to exposed con-ductors is limited to electrically qualified personnel; and overcurrent protective devices are operable and of appropri-ate interrupting rating. Even the safest procedures, when performed on poorly constructed or maintained equipment represent a risk to employees.

Flash Hazard AnalysisA large number of all serious electrical injures are related

to electrical arcs created during short circuits and switching procedures. In recognition of this, standards organizations such as the National Fire Protection Association (NFPA) have provided the industry with better techniques to evalu-ate both the magnitude of the electrical arc hazard and ap-propriate protective clothing and equipment.


Human errors and equipment malfunctions contribute to the initiation of an electrical arc. Engineering design and construction of arc resistant equipment as well as require-ments for safe work practices are continuing to target the risk of electrical arc flash hazards. An electrical arc is basi-cally an electrical current passing through ionized air. This current flow releases a tremendous amount of energy as both radiated light and convected heat. The amount of liberated energy is obviously dependent upon the system configura-tion, but the principle factors used in the determination of the hazard to personnel are as follows:1. Available short circuit current at the arc location2. Duration of the electrical arc3. Distance from the arc to personnel4. The arc gap5. Environmental conditions and surroundings at the arc

locationTo accurately assess the arc hazard, and make appropri-

ate decisions regarding personal protective clothing and equipment, it is necessary to fully understand the operation of the system under fault conditions. This requires both a short circuit analysis, in all likelihood down to the panel board level, and a protective devices coordination study. It isacommonmisconceptionthatarchazardsareaneffectof only high voltage. The actual arc hazard is based on avail-able energy, not available voltage. In certain conditions, a low voltage arc’s duration is longer than a high voltage arc. With this information available, the magnitude of the arc hazard at each work location can be assessed using several techniques. These techniques include:• NFPA 70E, Standard for Electrical Safety in the Work-

place, 2004 Edition• IEEE Std. 1584-2002, IEEE Standard for Performing

Arc Flash Hazard Calculations

Each of these techniques requires an understanding of anticipated fault conditions, and the limitation of the calculation method, both of which are beyond the scope of this paper.

The results of the arc flash hazard analysis are most use-ful when they are expressed in terms of the incident energy received by exposed personnel. Incident energy is commonly expressed in terms of calories per cm2 (cal/ cm2). Arc flash protective clothing is rated in terms of its Average Thermal Performance Value (ATPV), also expressed in terms of cal/cm2.

In addition to flame-resistant (FR) clothing and PPE, there are some safe work practices that can be adopted to minimize or eliminate the hazards. These practices include lockout/tagout along with temporary grounding, body posi-tioning, clothing, insulated tools, and other factors that must be carefully scrutinized to insure that the risk to employees is minimized. The first choice should be to minimize or eliminate the hazard; however, when this is not possible FR rated clothing and PPE must be utilized.

Worker wearing an FR Rated Flash Suit

National Electrical Code 2005 Flash Protection Requirements

The 2005 NEC Section 110.16 states, “Switchboards, panel-boards, industrial control panels, and motor control centers that are in other than dwelling occupancies and are likely to require examination, adjustment, servicing, or maintenance while energized shall be field-marked to warn qualified persons of potential electrical arc flash hazards. The marking shall be clearly visible to qualified persons before examination, adjustment, servicing or maintenance of the equipment.”

Recommended Warning Label

As with the electrical shock hazard, the easiest and most effectivewaytomitigatethearchazardistocompletelyde-energize the system for any type of maintenance activity.

Blast Hazard AnalysisAn electrical blast, or explosion, as it is often termed,

istheresultoftheheatingeffectsofelectricalcurrentandthe ensuing arc. This phenomenon occurs in nature as the thunder that accompanies lightning, a natural form of an electrical arc.


During an electrical arc, both the conducting material and the surrounding air are heated to extremely high tem-peratures. The resulting expansion of the air and vaporized conductive material creates a concussive wave surrounding the arc. The pressures in this wave may reach several hun-dred lbs./ft2, destroying equipment enclosures and throwing debris great distances. The pressure created during an electri-cal explosion is directly proportional to the available short circuit at the arc location. With a current short circuit study available, the anticipated blast pressure can be estimated fromtablesorcharts.[7]

Unfortunately, little canbedone tomitigate theblasthazard, at least in terms of personal protective clothing or equipment. Blast pressure calculations can be used to deter-mine whether enclosures will withstand an internal fault if sufficient manufacturer’s data is available. Again, it may be more important to merely recognize the magnitude of the hazard so that appropriate safety practices, such as correct body positioning, can be incorporated into work procedures. If the blast hazard is high, or if it is in a limited space, the blast can severely injure or kill a person. If these conditions are present, serious consideration should be given to not allowing personnel in the area during specific equipment operations.

Selection of Electrical Protective Equipment

Mostemployers,operators,andelectriciansareknowl-edgeable in the selection and inspection requirements for electrical PPE used for the prevention of electrical shock hazards, as well as head, eye, hand, and foot protective equipment. All of these requirements are readily found in OSHA 1910, Subpart I, Personal Protective Equipment. OSHA 1910.137, Electrical Protective Equipment, provides the requirements for the in-service care and use of electri-calprotectiveequipment.Unfortunately,mosthavelimitedknowledge or experience with regard to arc and blast hazards that may be associated with the maintenance and operation of energized electrical equipment and the necessary protec-tive clothing and PPE that is required.

The OSHA requirements for the hazard analysis and selection of protective clothing must first be defined.

OSHA1910.132,GeneralRequirements forPersonalProtective Equipment, paragraph (d) states “The employer shall assess the workplace to determine if hazards are pres-ent, or are likely to be present, which necessitates the use of Personal Protective Equipment (PPE). If such hazards are present, or likely to be present, the employer shall:

“Select, and have each employee use, the type of PPE thatwillprotect theaffectedemployee fromthehazardsidentified in the hazard assessment.”

OSHA 1910.132 (f ) – Training (1) states: The employer shall provide training to each employee who is required by this section to use PPE. Each such employee shall be trained to know at least the following:

• When PPE is necessary;• What PPE is necessary;• Howtoproperlydon,doff,adjust,andwearPPE;• The limitations of the PPE; and• The proper care, maintenance, useful life, and disposal

of PPE.”

Included in this hazard assessment should be the three electrical hazards; shock, arc, and blast. OSHA 1910.137 identifies the selection, inspection, and use requirements for electrical PPE. OSHA does not identify specific clothing that should be worn to protect the employee from the arc flash hazards but OSHA does specify what type of clothing is prohibited.

1910.269(l)(6)(ii) requires that “The employer shall train each employee who is exposed to the hazards of flames or electric arcs in the hazards involved.” Additionally, 1910.269(l)(6)(iii) states “The employer shall ensure that each employee who is exposed to the hazards of flames or electric arcs does not wear clothing that, when exposed to flames or electric arcs, could increase the extent of injury that would be sustained by the employee.”

“Note: Clothing made from the following types of fab-rics, either alone or in blends, is prohibited by this paragraph, unless the employer can demonstrate that the fabric has been treated to withstand the conditions that may be encountered or that the clothing is worn in such a manner as to eliminate the hazard involved: acetate, nylon, polyester, rayon.”

OSHA does, however, require protection from the hazards of electricity in 1910.335(a)(2)(ii) which states: “Protective shields, protective barriers, or insulating materi-als shall be used to protect each employee from shock, burns, or other electrically related injuries while that employee is working near exposed energized parts which might be ac-cidentally contacted or where dangerous electric heating or arcing might occur.”

If, during the operation, insertion, or removal of a circuit breaker, a fault occurs, the worker may be exposed to an electric arc with temperatures up to 35,000ºF as well as highlevelsofincidentenergy.Unprotectedworkersexposedto an increase in skin temperature of 203ºF for 0.1 second or 1.2 cal/cm2ofenergymaysuffersecondorthirddegreeburns and ignition of clothing. Protective clothing, includ-ing a complete multi-layered flash suit with hood and face shield, may be required for these activities.

The consensus standard for determining the necessary clothing and training is NFPA 70E-2004, “Standard for Electrical Safety in the Workplace.” In order to properly select rated clothing and PPE to provide this protection, the employer has but two options. The employer must calculate the incident energy (in cal/cm2) available at the work site, and the protective clothing required for the specific task, or as an alternative, use NFPA 70E Table 130.7(C)(9)(a) “Hazard/Risk Category Classifications” to identify the clothing required for the hazards associated with the specific task the employee is to accomplish. Caution must be used


if applying Table 130.7(C)(9)(a) because the short circuit current and protective device clearing time must be known per the notes at the end of the table.

Note: The employer must also determine a “Flash Pro-tection Boundary” in accordance with paragraph 130.3(A) for all energized work. At this boundary, exposed flesh must not receive a second-degree burn or worse.

Once it has been determined that protective clothing is necessary to perform the specific task, the necessary protec-tive clothing must be purchased and the employees trained to wear it properly.

SummaryIn resolving the issues of analyzing electrical hazards in

an industry, we must follow a path that will lead to a com-prehensive analysis of the problems that exist and provide a quantified value to ensure the selection of appropriate personal protection. An analysis of all three hazards, shock, arc, and blast must be completed and steps taken to pre-vent injuries. The following steps could be taken to ensure adequacy of the electrical safe work practices program and training of “qualified” electrical personnel:

1. Conduct a comprehensive Job Task Analysis.2. Complete a Task Hazard Assessment including:

a. Shock hazard.b. Arc flash hazard (using current Short Circuit and

Coordination Studies).c. Blast hazard.d. Other hazards (Slip, fall, struck-by, environmental,

etc.).3. Analyze task for the Personal Protective Equipment

needed.4.ConductTrainingNeedsAssessmentforQualifiedand

non-qualified electrical workers.5. Revise, update or publish a complete “Electrical Safe

Work Practices Program.”

Regulatory agencies and standards organizations have long recognized the need to analyze the hazards of elec-trical work and plan accordingly to mitigate the hazards. Unfortunately,manyintheelectricalindustryhavechosento “take their chances”, largely because nothing bad has yet to happen. As more information becomes available on the economic and human costs of electrical accidents, it is hoped that more in the industry will recognize the need for a sys-tematic hazard analysis, and an electrical safe work program that emphasizes hazard identification and abatement.

References[1] NFPA70E-2004,Standard forElectricalSafety in

the Workplace[2] OSHA29CFR1910,ElectricalStandards,Federal

Register Vol. 46, No. 11, Friday, January 16, 1981, Sup-plementary Information, I. Background, (3) Nature of Electrical Accidents, (a) Basic Contributory Factors.

[3] OSHA 29 CFR 1910.331-.335, Electrical Safety-Related Work Practices, August 6, 1990

[4] OSHA 29 CFR 1910.147, Control of HazardousEnergySource(Lockout/Tagout),September1,1989

[5] OSHA29CFR1910.269,ElectricPowerGenera-tion, Transmission, and Distribution, January 31, 1994

[6] OSHA Instruction STD 1-16.7, Directorate ofCompliance Programs, July 1, 1991

[7] RalphH.Lee,“PressuresDevelopedbyArcs”,IEEETransactions on Industry Applications, Vol. IA-23, No. 4, p. 760, July/Aug. 1987.

DennisK.Neitzel,C.P.E.,DirectorofAVOTrainingInstitute,Inc.,Dallas,Texas,hasover37yearsexperienceinElectricalUtilityandIndus-trial facilities electrical systems. He is an active member of IEEE, ASSE, NFPA, AFE, and IAEI. He is a Certified Plant Engineer (C.P.E.) and a CertifiedElectricalInspector-General.Mr.NeitzelearnedhisBachelor’sdegreeinElectricalEngineeringManagementandhisMaster’sdegreein Electrical Engineering Applied Sciences. He is also a Principal Com-mitteeMemberfortheNFPA70E,StandardforElectricalSafetyintheWorkplace;servesastheWorkingGroupChairmanforrevisingIEEEStd.902(TheYellowBook),IEEEGuideforMaintenance,Operation,and Safety of Industrial and Commercial Power Systems; is co-author of theElectricalSafetyHandbook,2ndEdition,McGraw-HillPublisher;and serves as the ASSE Engineering Practice Specialty’s ByDesign NewsletterEditor.Mr.NeitzelreceivedtheEngineeringPracticeSpe-cialty“SafetyProfessionaloftheYear”awardfor2003-2004fromtheAmerican Society of Safety Engineers.


Electrical PPE TrendsNETA World, Fall 2005 Issue

by Bill RiethSalisbury

NFPA 70E is raising the level of awareness for electrical safety in the workplace. PPE (personal protective equip-ment)isanimportantelementtoworkingsafely.Moreandmore companies are developing electrical safety programs and providing better training for employees who work on or near exposed energized electrical equipment.

Virtually unused as little as 5 or 6 years ago, lockout/ta-gout(LOTO)programsarenowcommonintheworkplace.Likemanysafetyproceduresthatareimplemented,LOTOprograms were not met with open arms when they were first introduced. Concerns included time delays, cost of equip-ment, and cost of additional training. However, it quickly became evident that the cost saving benefits of reducing injury far outweighed any other perceived costs that may have existed. As a result, today’s electrician or maintenance person would not think of working on a piece of equipment that was not locked-out or tagged-out.

Along with the advancements of electrical safety aware-ness, there have been advancements of electrical PPE. One of the most difficult aspects of implementing a successful electrical safety program is to ensure the worker is actually using the PPE in the field. One of the best ways to ac-complish this is to make the necessary PPE as unintrusive as possible. The less the required PPE hinders a worker, the more likely the worker is to wear it. With this in mind, manymanufacturershavemadeanefforttoprovidelighterweight clothing, lighter tinted face shields, and thinner voltage rated rubber goods to allow for easier use of these products by the worker.

Arc-flash clothing has become much more comfort-able to wear in the last few years. Flame resistant fabrics that are rich in cotton content are better moisture move-ment vehicles than synthetic FR fabric alternatives. FR cotton blends allow a person’s body to radiate itself cor-rectly by allowing the passage of air through the fabric. The human body cools itself by perspiring, but it is not the perspiration on the skin that does the cooling. It is the evaporation of perspiration that cools the body down.

Arc flash face shields have undergone dramatic changes. ASTMF2178-02isthestandardusedtotestarcflashfaceshields and includes very specific requirements. The shield must not only dissipate heat, it must also protect the eyes

This evaporation occurs when air is introduced to the skin. One more advancement in FR fabrics is the performance of physically lighter FR cotton and cotton blends in higher cal/cm² exposures. For instance, a 7 oz FR cotton blend fabric has an 8.2 cal/cm² rating yet feels much like a nor-mal work shirt or pant. These garments are put through a rigorous laundering test to ensure that they maintain their FR properties through repeated washings. Regular proper laundering of the garment ensures that there are no contaminants which may add to the flammability of the garment and also improves the probability that it will be worn by the worker.


from the bright light emitted during an arc flash. Just 18 months ago the highest rated hard hat mounted face shield had a rating of 10cal/cm². The tinting of the shield at that time was dark and made identifying certain wire colors diffi-cult.Todaysomemanufacturersprovidefaceshieldsoffering15 cal/cm² protection level while providing a much clearer lens.Lighttransmissionisthekeytermwhendiscussingclarity of a face shield. The higher percentage of the light transmission rating will improve color recognition of wires. Normal safety sunglasses have a light transmission rating of less than 20 percent while a clear shield typically has a light transmission rating of 85 percent.

Proper cover-up for equipment is also an area of con-cern for companies today. It is common to be working on a properly de-energized and locked-out tagged-out piece of electrical equipment but still be positioned in close proximityofenergizedequipment.Mostincidentsinvolv-ing electrical contact are due to accidental or incidental contact or what is more commonly called brush contact. There are rubber insulating materials in the market spe-cifically designed to ensure that this type of contact does not occur. One variation of this material, known as roll blanketmaterial,comesintwodifferenttypesandisavail-able in three levels of voltage protection, Class 00 (max 500 V), Class 0 (max 1000 V), and Class 1 (max 7,500 V).

These low voltage gloves are perfect for today’s commer-cial and industrial applications. Due to the thinness of these classes of gloves, they are much easier to work in. Theyoffergreatfeelanddexterityallowingtheworkerstoperform tasks with little difficulty while allowing them to work safely.These gloves complywithASTMStandardD120. The gloves should be dielectrically retested every six monthsfromthedateofissueforservice.Glovesnotissuedfor service shall not be placed into service unless they have been electrically tested within the previous twelve months perASTMF496 andOSHACFR291910.269.Thereare independent glove testing laboratories throughout the country that can perform this service.

Another option that is catching on in the industry is what is being called an alternating color program. In this program thedecisionismadetousetwodifferentcolorsofgloves.Class0and00TYPEInonozoneresistantnaturalrubbergloves come in various colors . Class 0 and 00 gloves are also availableinEPDM(TYPEII)rubberinbluecolor.Asanexample, a company could decide to use red gloves for six months. At the end of six months the red gloves would be taken out of service or sent out for retesting. The workers would then be issued black gloves for the next six months. This program ensures not only that the electrically tested gloves are up to standard, but it also allows easy visual veri-fication that the worker is using electrically-tested gloves.

TheuseofleatherprotectorsthatcomplywithASTMF696 should be used with all rubber insulating gloves.

It is extremely important to remember that voltage rated gloves are the only electrical safety items designed for intentional contact with an energized piece of equipment; therefore, it is extremely important to both air test and visually inspect rubber gloves prior to each use.

Everyday tools used for maintenance have been made into PPE items. Insulated tools that are manufactured to theASTMF1505standardandratedformaximumvoltageof 1000 Vac will provide workers with additional protection. The 2004 edition of NFPA hazard risk category table 130.7 (C)(9)(a) requires insulated tools for certain tasks.

The electrical hazard and the level of the hazard must be identified prior to selecting your PPE. The 2004 edition of NFPA 70E standard makes it easier than ever to develop and implement an electrical safety program. By following the requirements for electrical PPE outlined in NFPA 70E, along with the advancements in today’s electrical PPE, companies can ensure workers are performing daily tasks safely.

BillRieth,RegionalManager/TrainerforSalisbury.Billisaleadingindustry trainer of arc flash safety. He was instrumental in developing Salisbury’s PPE program for the electrical industry on arc flash protec-tion. He is a member of NFPA, IEEE, and participates in training for NJATC. He has extensive knowledge of NFPA 70E and OSHA in regard to electrical safety including the issue of arc flash safety and the proper selection of PPE.

The second type is a clear PVC material with a Class 1 rat-ing. Both of these materials are designed to be cut to size for the application and are extremely flexible and easy to install. The use of insulating material will reduce the opportunity of an arc flash incident and reduce shock potential.

Manypeople in the industry still view voltage glovesas cumbersome and difficult to use. These people envision the typical lineman’s glove, such as a Class 2 glove which is rated for up to 17 kV work, as the glove they would need to use in lower voltage tasks. Because of this perception, many people decide not to use voltage gloves at all. Not only are these people exposed to unnecessary risk of injury, they are not complying with the law which requires voltage gloves to be used when working on or near 50 volts or more. Voltage gloves are now available in Classes 00 and Class 0.


Proper PPE — A Journey with No End:One Company’s Experiences


by Tony DemariaTony Demaria Electric, Inc.

Forty-two years ago, when starting my apprenticeship in anIBEWshopintheLosAngelesarea,therewasnoPPEat the shop. One exception was a very old, heavily scratched face shield. It was sometimes found in the vicinity of the grinding wheel. When the grinding produced a large enough quantity of sparks to prevent work from being done, the shield was used. For small delicate work, the face shield was left where it lay, as it could not be seen through.

In four years of working in that shop, there were no safety meetings and no formal safety training. As I recall, nosafetytrainingwasofferedatLosAngelesTradeTech-nical College where the apprenticeship classes were held. Safety was taught “on the job,“ where one of the senior journeymanexplainedhowtotellthedifferencebetween120 and 480 volts. This was performed using two fingers of one hand only. We were reminded of the importance of not usingfingersofdifferenthandsasthiscouldleadtoabadconsequence,suchasdeath.Thedifferenceinvoltagescouldbe distinguished by the tingling in your hand. The more tingling you felt, the higher the voltage. For those readers not up to date on recent advances in safety, this method is no longer acceptable.

GoingtoworkfortheLosAnglesDepartmentofWaterand Power produced structured safety training. There were monthly safety meetings.

The majority of the work was medium and high voltage with the associated higher risks. One training topic was resuscitation. It was not called CPR at the time. This proved valuable as within a short time I was provided an opportu-nity to assist a child using the rescue breathing technique recently taught.

The results of both job experiences, however, appeared to be approximately the same at work. There was an endless stream of cuts, bruises, and strains. Broken bones and fatali-ties were part of the mix. One hydroelectric construction

project I worked on had one fatality a year for three years with no change in safety practices or management concerns. This was all accepted without question as part of working in a dangerous environment.

In the 70’s we began to hear this dreaded word — OSHA. These guys were going to screw up everything. How could one possibly perform a job with a lot of rules to confuse everybody?Evenworse,wearingabunchofstufflikesafetybelts and gloves for easy tasks would only slow down the work.

Two incidents that occurred very close to me changed my attitude. One involved a coworker falling from ap-proximately 20 feet onto some protruding steel. He almost bled to death in my arms. Only luck and a close hospital saved his life. In the other incident, the electrician was not as fortunate and it ended in a fatality.

When starting an electrical contracting business 30 years ago,safetywasnotthefirstthingonmymind.Gettingthejob done and making money were the priorities. This soon changed as the enormity of the situation became apparent. I faced a huge responsibility for the safety of the electricians performing the work.

What could I do to ensure that all personnel went home every night with all body parts working correctly, and, most importantly, alive! Working safe involves several elements — PPE is only one. The first step is always to insure the safest working environment possible. If the equipment being workedonisenergized,thefirstchoiceistoturnitoff.Ifthefloor is slippery with oil, the number one thought should be to clean the floor, not “be careful of your surroundings.”

This short article is not an overview of safety. The focus is PPE and how far we have come in a few short years. Mostimportantly,whatcanwedonow?ThetwoincidentsI referred to above would never have happened had bet-ter safe practices been in place. However, had PPE been


utilized (a safety harness and voltage-rated gloves) when bad things happened and mistakes made, no one would have been hurt.

Here lies one danger of PPE. It has been and can be used as the first line of safety. Do not fall into this trap. Another danger of PPE is once it is put on, the electrician may get a feeling of invulnerability. Wearing all this gear, you can feellikeSuperman.Youarenot stronger and may even have reduced awareness such as limited vision with a flash hood on.Thisisacomplexsubjectandsometimesoffersconfusingoptions as to what is the best choice.

Meeting the Challenge of PPE Safety1. How can employers and employees understand and

conform to the frequently changing laws, standards, regulations and customer rules on PPE?• Attend conferences, especially the IEEE PCIC/IAS

Electrical Safety Workshop that has many sessions specifically on PPE.

• Read a book! There are currently several excellent new safety books listing appropriate PPE. Check the NFPA and IEEE on-line bookstores.

• Go to special safety training schools. Offers fre-quently come in the mail and can be found on-line. Schools vary from one day to two weeks.

• Hire a consultant who is knowledgeable on PPE. An expert fromoutsidethecompanymayofferuniqueexpertise and insights.

2. Exactly what PPE should be purchased with a limited budget to get the best product available at that time?• Talk with the manufacturers of PPE and invite them

to your shop to demonstrate their equipment. This is free and carries no obligation.

• Purchaseseveraldifferenttypesanddistributethemto employees to test, evaluate, and report back their findings.

• Call other companies using similar PPE and ask their opinion. A network of like-minded organiza-tions can provide valuable information.

3. How does a company involve all field personnel in the creation and implementation of the policies on PPE?• At your weekly safety meeting, allow specific time to

review what PPE is being used and feedback as to what worked best or what problems were encoun-tered.

• Form a specific safety committee to examine one product item, such as arc flash protection, and allow them time for a thorough evaluation.

• Rotate committees frequently to make sure all field personnel have the opportunity to participate.

The responsibility of every company is to insure that the best PPE currently manufactured is available to its field personnel. However, it does not end here. The problem is making sure the PPE is used! Involving all employees in the process is the best way to succeed in meeting this challenge.

The experiences at our company have not always been positive. There have been hurt feelings, angry words, and wasted money on bad equipment. Management getsfrustrated when PPE is underutilized, and everyone gets overwhelmed by all the unending changes. But here is the good news. The workers compensation modification rate earned by our company is the lowest possible, saving tens of thousands of dollars per year. Why? Because we work much safer than in earlier years. Accidents have decreased radically.

The best news is deeper. We do not wear PPE to save money on insurance or because some rule says we must. PPE is bought, cared for, and worn because it is the right thing to do. We really care and look out for each other. A new culture is building that tells us safety is a moral decision. It’s a good way to go to work.

All this is a never-ending, on-going process to be repeated over and over. Remember, having and using the proper PPE is a journey, not a destination!

Tony Demaria served an IBEW Apprenticeship starting in 1963 andthenworkedforLosAngelesDepartmentofWaterandPowerinsubstation maintenance for eight years. He has owned and operated Tony Demaria Electric for over 25 years, specializing in maintenance and testing switchgear and large motors for industrial facilities. Tony Demaria Electric is a NETA Accredited Company, and Tony serves on the NETA Safety Committee.


Empowering Safety


by Charlie SimpsonBurlington Electrical Testing Co.

Part I — From Gloves to Arc Flash Suits Employers Must Provide, Maintain and Ensure the Proper Use of their Employees’ PPE

The Occupational Safety and Health Administration (OSHA) (www.osha.gov) states that employees who per-form work involving electric power generation or distribu-tion are exposed to “a variety of significant hazards, such as fall, electric shock, and burn hazards, that can and do cause serious injury and death.” In fact, OSHA calculates that an average of 444 serious injuries and 74 fatalities occur annually among these workers.

In just about every type of industrial work setting, more and more workers are using personal protective equipment (PPE) to help protect them from injury and even death. If any industry exemplifies the need for continued safety practices, it is the electric power generation, transmission, and distribution industry.

From performing infrared scans to complete shutdown repair, employee safety is more critical than ever. Federal and stateagenciesarelettingoffendersknowthisfactthroughsteep fines levied against employers.

Responsibility: Where to StartIdeally speaking we are all responsible for safe work

habits and environments. Realistically, with tight deadlines and budgets, employees may not always opt for the safest versus the more efficient method of performing an opera-tion. OSHA, however, makes it clear that employers are ultimately responsible for the safety of their employees, including providing the proper PPE. Of course this does not mean employees are not culpable for their actions or inactions, but all infractions should be acted on and docu-mented by the employer.

For live electrical work, there are no gray areas. OSHA requires nothing less than compliance when it comes to employee safety. Where a specific article may not apply, OSHA’s general duty clause covers it all. The general duty

clause is defined in the Occupational and Safety Health Act of 1970 – Section 5 (a) and states “Each employer (1) shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees; (2) shall comply with occupational safety and health standards promulgated under this Act.”

A good place for employers to start protecting their em-ployees is with an in-house safety guide or policy manual. Written by your company safety officer, the manual may be reviewed by both employees and management to determine areas for improvement and then reviewed annually or as needed to incorporate regulatory changes or technology advancements. A safety manual should define the safety director’s responsibilities, the supervisor’s responsibilities, the employees’ responsibilities, as well as any subcontractor’s responsibilities to ensure safe work practices.

Other areas that one may want to consider when out-lining a safety guide are forming and maintaining a safety committee, scheduling safety training, equipment and facil-ity inspection checklists, accident reporting procedures and investigation forms, emergency response guidelines, and best practices for using and maintaining PPE.

Per OSHA 1910.335(a)(1)(i) Safeguards for Personnel Protection. An employer is responsible for providing em-ployees with all appropriate work-related PPE. Employers must insure that employees are correctly trained in the use and maintenance of the PPE and that employees are actu-ally wearing the PPE on the job sites.

Training can be provided by local universities or colleges; by county, state, and federal government agencies such as OSHA; by union academies; and by various independent training companies and PPE providers, either on your site or atatrainer’sfacilities.Keepingrecordsofalltraininglevels,

(See page 58 for Part Two)


courses taken, and certifications achieved by all employees in a single location will ease reference. Additional educa-tion should include training in first aid and CPR through a certified organization such as the American Red Cross.

New Laws Coming?On June 15, 2005, OSHA listed several proposed rule

changes to its PPE guidelines, due to the fact that the exist-ing standard for the construction of electric power trans-mission and distribution equipment (contained in Subpart V of OSHA’s construction standards (29 CFR part 1926) was promulgated in 1972, over 30 years ago.

According to OSHA Federal Register Docket No. S-215, “Employees maintaining or constructing electric power transmission or distribution installations are not adequately protected by current OSHA standards, though these employees face far greater electrical hazards than those faced by other workers. The voltages involved are generally much higher than voltages encountered in other types of work, and a large part of electric power transmission and distribution work exposes employees to energized parts of the power system.”

The document further states that “Some of the technol-ogy involved in electric power transmission and distribu-tion work has changed since then, and the current standard does not reflect those changes.” For example, the method of determining minimum approach distances has become more exact since 1972, and the minimum approach distances given in existing Sec. 1926.950(c)(1) are not based on the latest methodology.

Also according to the proposed changes, “Interpreting existing Sec. 1910.136(a) so as to recognize electrical hazard footwear as a primary form of electrical protection could ex-pose employees to electric shock hazards if they believe that the real primary form of electrical protection (for example, rubber insulating gloves or blankets) is no longer neces-sary. This is true for several reasons. First, electrical hazard footwear only insulates an employee’s feet from ground. The employee can still be grounded through other parts of his or her body. Second, the insulation provided by electrical hazard footwear is good only under dry conditions. This footwear provides little if any protection once it becomes wetordamp.Lastly,thevoltageratingonelectricalhazardfootwear is only 600 volts.”

The proposal maintains that because of these limitations, electrical hazard footwear “should not be addressed by Sec. 1910.136, which is designed to provide protection to employees’ feet. The need for conductive footwear, whether or not it provides protection for the foot, is adequately ad-dressed by the general requirement in Sec. 1910.132(a) to provide personal protection equipment. Therefore it is pro-posed to delete language relating to electrical hazards from Sec. 1910.136(a).” Hearings on these changes are scheduled to be held December 2005 in Washington, DC.

Protecting Against Arc Flash The electric power distribution industry has been address-

ing safety, including shock, burns and blast, in stages for more than 30 years. The area of rising concern is for arc flash protection. From insulated gloves and safety goggles, to fire resistant clothing and arc flash suits, PPE is helping reduce injuriesandfatalities.However,PPEisonlyeffectivewhenused, and used properly. Not surprisingly, the major driving force behind this safety initiative is NFPA 70E 2004.

Published by the National Fire Protection Association (www.nfpa.org), NFPA 70E 2004 Edition is a voluntary standard for electrical safety in the workplace. Per the fore-word, NFPA 70E was created because “… a need existed for a new standard tailored to fit OSHA’s responsibilities, that would be fully consistent with the National Electrical Code (NEC).” This standard creates thresholds for worker protective apparel based on exposure to arc hazard risk and is designed to protect workers that install, maintain, or repair electrical systems.

Although NFPA 70E is not a law, companies are expected to maintain a safe place of employment for their workers, including appropriate protection from electric arc flash. OSHA 1910.335(a)(1)(i) states, “Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment

NIOSH ConclusionsConclusions, seemingly obvious, found in NIOSH reports have stated that employers need to:

• Haveastandardoperatingprocedure(SOP)thatstates that all high voltage work is performed by qualified persons.

• Haveapropergroundinplaceforallelectricaltransformers and equipment.

• HaveanSOPthataddressestheproceduresfora lockout/tagout system.

• Haveallpowerpanelsandtransformerslabeledso that it is evident where electricity is provided and from which panels.

• Train employees in theproperuseofpersonalprotective equipment (PPE).

• Have an SOP that addresses environmentalconditions (rain, snow, lightning, etc.) during certain types of work activities, such as high voltage electrical work.

• HaveanSOPstatingthatthereisanemployeelocated within a short distance of any employee working with high voltage equipment in case of an emergency.


that is appropriate for the specific parts of the body to be protected and for the work to be performed.” But before one can determine the proper arc flash protection, an arc flash and shock hazard analysis must be performed.

An arc flash hazard analysis is the first step toward deter-mining the proper PPE, along with the arc flash boundaries. This analysis can then be an integral part of an employer’s overall electrical safety program.

An arc flash hazard analysis will allow calculation of the incident energy, which is the energy from an arc flash per unit area on a surface located at some distance away from the flash location. The working distance is the distance from where the worker stands to the flash location. IEEE Std 1584 uses 18 inches for everything except low-voltage power circuit breakers, which have a cabinet depth of about 24 inches. IEEE Std1584 also uses 36 inches for voltages above 600 V to its 15 kV limit. It is the incident energy generated during an arc flash that causes burns to the skin. The typical unit of incident energy is the cal/cm2.

Although there are various methods of calculating values of available heat energy from an electric circuit, OSHA “will not endorse any of these specific methods.” Each method requires parameters, such as fault current, the expected length of the electric arc, the distance from the arc to the employee, and the clearing time for the fault – that is, the time the circuit protective devices take to open the circuit and clear the fault.

It should be noted that both the NFPA 70E and IEEE Std 1584 use the assumption that an arc flash generating 1.2 calorie/cm2 (1.2 calorie/cm2 = 5.02 joules/cm2 = 5.02 watt-sec/cm2) for 0.1 second will result in the onset of a second-degree burn. It is assumed that a second-degree burn will be curable and will not result in death. A first degree burn is the equivalent of a sun burn; second degree burns will blister, but the skin will heal; third degree burns result in permanent damage and scarring of the skin and internal tissue.

Figure 1 — Rubber gloves, one of the most prevalent pieces of PPE are manufactured to at least twice the mandated thickness providing the first line of defense for electrical power distribution workers

PPE TechnologiesThe technology that comprises PPE continues to evolve

in the electrical industry. Today the range of PPE can in-clude primary and secondary insulation products, as well as additional equipment such as:

1. RubberGloves(withLeatherProtectors) 2. Rubber Sleeves 3. Fire Resistant Everyday Work Wear 4. Hot Sticks 5. Insulated Hand Tools 6. Blast Blankets 7. PortableGrounds 8. RubberMatting 9. Arc Flash Suits 10. Lockout/TagoutSystems

Primary insulation, such as rubber gloves and rubber blankets normally insulate an employee directly from an energized part. Secondary insulation such as footwear and matting normally insulates an employee’s feet from a grounded surface (See New Laws Coming for changes in footwear classifications).

Each employee should inspect his or her own PPE at the beginning of each work period and again before each use, while the company safety officer should establish a periodic review of all PPE.

Part 2 of Empowering Safety in the Winter issue of NETA World provides PPE purchasing tips including glove and fire resistant clothing ratings as well as suggestions on how to help ensure employees wear the appropriate PPE.

Charlie Simpson is the Technical Writer for Burlington Electrical Testing Co. (BET, www.betest.com, Croydon, PA). BET, a NETA Ac-credited Company, is an independent electrical testing and maintenance company servicing the industrial, commercial, construction, medical and utility industries for all manufacturers of power generation and distribu-tion equipment in the low to EH voltages.

AcknowledgementsBET appreciates the contributions of Peter Senin, presi-

dentofBurlingtonSafetyLabsandKevinMcLaughlinofTyndale who contributed their expertise to this article, and thanks Jim White of Shermco for reviewing the accuracy of this article.

PhotocourtesyofBurlingtonSafetyLaboratory,Inc.


Do I Have to Comply with NFPA 70E?


by Lynn HamrickESCO Energy Services Company

Muchinformationandguidanceisbeingprovided,froma variety of sources, with respect to NFPA 70E compliance. This narrative provides background information on the evolution of NFPA 70E and the current regulatory activities associated with this standard. Additionally, it simplifies and condenses the available information into viable recommen-dations for implementing applicable requirements.

Does OSHA Require compliance to NFPA 70E-2004?

When discussing NFPA 70E with personnel at indus-trial facilities, one of the first questions they ask is, “Does OSHA require compliance to this standard?” In answering this question, one must first consider some background information associated with existing OSHA standards and this particular standard.

Following the Occupational Health and Safety Act of 1970, OSHA adopted the 1968, and then the 1971, edition of NFPA 70, National Electric Code, under Section 6(a) of the Act. Subsequent changes or additions to the OSHA requirements would require performing the process out-lined in Section 6(b) of the Act, which requires a public notice or an opportunity for public comment and public hearings. This is an expensive and lengthy process at best. Unfortunately,OSHAfoundthattheNEC was lacking in many aspects of electrical safety. The NEC primarily deals with the design and construction of electrical installations. However, OSHA’s responsibilities include the employers and employees in the workplace, and the NEC does not address the requirements for electrical safety-related work practices associated with the operation and maintenance ofelectricalsystems.Realizingthisdifference,theNationalFireProtectionAssociation(NFPA)offereditsassistanceinpreparing a document “to assist OSHA in preparing electri-cal safety standards that would serve OSHA’s needs and that could be expeditiously promulgated through the provisions

of Section 6(b) of the Occupational Safety and Health Act.” The resulting Standard for Electrical Safety Requirements for Employee Workplaces, NFPA 70E, was first issued in 1979 with the specific purpose of being a companion document to the NEC.

Subsequent to the initial versions of NFPA 70E, OSHA standard 29CFR1910.331-335, commonly referred to as Subpart S — Electrical Standards, was issued in 1990. This standard deals with requirements associated with electrical safety-related work practices for industrial facilities. In general, this OSHA standard only addresses the electrical shock hazard and does not specifically address electrical arc flash or arc blast hazards. It includes a description of the application of the standard (Section 1910.331), employee training requirements (Section 1910.332), safety-related work practices (Section 1910.333), limitations in the use of equipment (Section 1910.334), and required personnel protection safeguards (Section 1910.335). This standard delineates requirements for qualified persons which include being familiar with the standard as well as being trained and familiar with the work being performed. It also requires appropriate safety signage to warn employees of electrical hazards and states that “employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appro-priate for the specific parts of the body to be protected and fortheworktobeperformed.”Unfortunately,itdoesnotspecifically define what the appropriate electrical protective equipment is for the potential electrical hazard. However, this requirement does imply that the magnitude of the electrical hazard should be known and that the protective equipment should be selected accordingly.

Inanefforttofurtherdefinetherequirementsforelec-trical safety, the fifth edition of NFPA 70E was published in 1995. This standard introduced the concept of limits of approach, and the establishment of a flash protection bound-ary was introduced. In the sixth edition, published in 2000,


further focus on flash protection and the use of personal protective equipment (PPE) was expanded with charts be-ing added to assist the user in applying PPE for common tasks. With the most recent seventh edition, published in 2004, the standard was rearranged to be consistent with the NEC and was renamed Standard for Electrical Safety in the Workplace.

Another OSHA requirement, NFPA 70, the National Electric Code, further amplifies these requirements in its 2002 edition. It defines a qualified person as, “One who has skills and knowledge related to the construction and operations of the electrical equipment and installations and has received safety training on the hazards involved.” NEC - 2002 also provides specific language associated with arc flash hazards:

“Section 110.16 Flash Protection. Switchboards, panelboards, industrial control panels, and motor control centers in other than dwelling occupancies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.FPN No. 1: NFPA 70E-2000, Electrical Safety Re-quirements for Employee Workplaces, provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.”[4]

With the 2002 edition of the NEC, arc flash protection has been introduced into the requirements. Further, NFPA 70E-2004 has been provided as a source document for de-termining the magnitude of the hazard and the appropriate protective measures to be taken to safeguard employees.

What should be derived from the above discussion is that NFPA 70E is considered an industrial consensus standard and is intended for use by employers, employees, and OSHA. OSHA has not adopted NFPA 70E as it did earlier ver-sions of the NEC simply because adoption would require the lengthy and expensive process outlined in Section 6(b) of the Act. OSHA has instead referenced compliance to NFPA 70E in a recent citation using Section 5(a)(1) of the Occupational Safety and Health Act of 1970, commonly referred to as the “general duty clause,” as their basis for this citation. The general duty clause states that employers “shall furnish to each of its employees employment and a place of employment which are free from recognized hazards that are causing or likely to cause death or serious physical harm to his employees.”

This methodology for implementing potentially new requirements through the use of industrial consensus stan-dards, like NFPA 70E, is common practice by OSHA. In a recent standard interpretation letter dated 7/25/03, OSHA’s Russell Swanson stated, “Industry consensus standards, such as NFPA 70E, can be used by employers as guides to

making the assessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions, they can be used as evidence of whether the employer acted reasonably.” Further indications from OSHA’s website state that proposed changes to OSHA’s general industry electri-cal installation standard (1910 Subpart S) focus on safety in the design and installation of electric equipment in the workplace. The changes draw heavily from the 2000 edi-tion of the National Fire Protection Association’s (NFPA) Electrical Safety Requirements for Employee Workplaces (NFPA 70E), and the 2002 edition of the National Electri-cal Code (NEC).”

It is clear from the above evidence that OSHA is using NFPA 70E as an industrial consensus standard. Further, OSHA expects employers and employees to comply with the provisions of NFPA 70E regardless of whether or not it has been adopted as an OSHA requirement.

What Does NFPA 70E-2000 Compliance Mean for My Facility?

The next question one has to ask is, “How will NFPA 70E complianceaffectme?”NFPA70E–2004andtheNEC - 2002 require and/or recommend that facilities provide:

• Asafetyprogramwithdefinedresponsibilities• Electricalhazardsanalyses• Personalprotectiveequipment(PPE)forworkers• Trainingforworkers• Toolsforsafework• Warninglabelsonequipment

NFPA 70E further requires that safety-related work prac-tices shall be used to safeguard employees from injury while they are working on or near exposed electric conductors or circuit parts that are or can become energized. The specific safety-related work practice shall be consistent with the nature and extent of the associated electric hazards. These work practices shall include wearing protective clothing and other personal protective equipment (PPE) when working with the flash protection boundary.

With regard to arc flash hazards, a “flash hazard analysis shall be done in order to protect personnel from the pos-sibility of being injured by an arc flash. The flash hazard analysis shall determine the Flash Protection Boundary and the personal protective equipment that people within the Flash Protection Boundary shall use.”

This standard also provides some descriptions associated with working distances, or boundaries, with respect to be-ing a qualified versus unqualified person. These boundaries are as follows:

• Flash Protection Boundary — The distance at which the incident energy from the live part is equal to 1.2 cal/cm2, the limit for a second-degree burn on bare skin. Persons must not cross this boundary unless they are


wearing appropriate personal protective clothing and are under close supervision of a qualified person.

• Limited Approach — The distance at which barriers should be placed to protect unqualified personnel from an electrical hazard. Only qualified persons and escort-ed unqualified persons are allowed to enter a limited space.

• Restricted Approach — The distance at which only qualified personnel are allowed with appropriate pro-tective clothing and personal protective equipment for the associated hazard. No unauthorized conductive ma-terial and no unqualified persons are permitted to cross a restricted boundary. Further, a documented and man-agement-approved plan is required to enter a restricted space.

• Prohibited Approach — The distance at which quali-fied personnel should not introduce grounded equip-ment or material not insulated for the voltage rating due to the possibility of flashover. A documented and man-agement-approved risk analysis and plan are required to enter a prohibited space.

A pictorial representation of these boundaries is provided in figure C.1.2.4 from NFPA 70E, reproduced below.

IEEE 1584-2002 guidelines have been derived as a result of extensive testing and, therefore, are typically considered tobemoreaccurate.Useofeithermethodologyshouldbeconsidered acceptable.

With regard to determining appropriate work practices and PPE, the magnitude of the potential arc flash hazard is first determined based on work being performed, the exposure to the employee, and the potential incident energy of an arc flash. The appropriate PPE is then selected with guidanceprovidedinthePPEMatrix,NFPA70ETable130.7(C)(10). Further guidance on protective clothing char-acteristics is provided in NFPA 70E Table 130.7(C)(11).

With regard to what an employer should already be doing to minimize the exposure of employees to energized circuits, the NEC has provided guidance:“110.27 Guarding of Live Parts. (A) Live Parts Guarded Against Accidental Contact.

Except as elsewhere required or permitted by this Code, live parts of electrical equipment operating at 50 volts or more shall be guarded against accidental contact by approved enclosures or by any of the fol-lowing means:1. By location in a room, vault, or similar enclosure

that is accessible only to qualified persons.2. By suitable permanent, substantial partitions or

screens arranged so that only qualified persons have access to the space within reach of the live parts. Any openings in such partitions or screens shall be sized and located so that persons are not likely to come into accidental contact with the live parts or bring conducting objects into con-tact with them.

3. By location on a suitable balcony, gallery, or plat-form elevated and arranged so as to exclude un-qualified persons.

4. By elevation of 2.5 m (8 ft) or more above the floor or other working service.

(B) Prevent Physical Damage. In locations where elec-tric equipment is likely to be exposed to physical damage, enclosures or guards shall be so arranged and of such strength as to prevent such damage.

(C) Warning Signs. Entrances to rooms and other guarded locations that contain exposed live parts shall be marked with conspicuous warning signs for-bidding unqualified persons to enter.”

For the employer, this requires that guards be provided for all exposed circuitry, even within commonly opened switchboards, panelboards and industrial control panels, to ensure that the risk to employees is minimized. A logical inference from the NEC requirements stated above is that the provided guards should also accommodate and safeguard employee’s exposure to an associated arc flash hazard.

Flash protection boundary

Limited approach boundary

Limited boundary/space

Restricted approach boundary

Any point on an exposed, energized electrical conductor or circuit part

Restricted apace

Prohibited approach boundary

Prohibited space

To accommodate the work practices stated above for many common tasks, NFPA 70E Table 130.7(C)(9)(a) has been provided for use. However, specific fault currents and fault clearing times were assumed in the preparation of those tables. The assumed short circuit current capacities and fault clearing times are listed in the notes of the table. If the faultcurrentsorfaultclearingtimearedifferentthanthoseused in generating the recommendations in the table, the incidentenergycanbeverydifferent.Thesetablesaresuit-able for their intended use, providing an immediate answer, but are not a substitute for performing a more detailed arc flash hazard analysis specific to the facility. Analyses that take into consideration the true operating conditions of a specific facility can be performed using the methods outlined in either NFPA 70E or IEEE Standard 1584-2002. The


In summary, OSHA expects employers and employees to comply with the provisions of NFPA 70E regard-less of whether or not it has been adopted as an OSHA requirement.

NFPA 70E compliance for a facility involves putting an electrical safety program in place, which will identify and analyze electrical hazards in the workplace, educate the workforce on those hazards, require the use of appropriate PPE, and implement warning labels and guards to protect the workers.

References[1] NFPA70E,Standard for Electrical Safety in the Work-

place – 2004 Edition, Forward to NFPA 70E.[2] OSHAStandard29CFR1910,Section.335(a)(1)(i).[3] NFPA70,National Electric Code – 2002 Edition, Sec-

tion 100, Definitions.[4] NFPA70,National Electric Code – 2002 Edition, Sec-

tion 110.16, Flash Protection.[5] Occupational Safety Health Act of 1970, Section

5(a)(1).[6] OSHAStandardInterpretationsdatedJuly25,2003,

“General Duty Clause (5(a)(1)) citations on multi-employer worksites; NFPA 70E electrical safety re-quirements and personal protective equipment.”

[7] OSHATradeReleasedatedApril2,2004,“OSHAProposes Revisions to Electrical Installation Stan-dard.”

[8] NFPA70E,Standard for Electrical Safety in the Work-place – 2004 Edition, Section 110.8(A).

[9] NFPA70E,Standard for Electrical Safety in the Work-place – 2004 Edition, Section 130.3.

[10]NFPA70E,Standard for Electrical Safety in the Work-place – 2004 Edition, Section 130.7(C)(9)(a).

AsOperationsManagerofESCOEnergyServicesCompany,Lynnbrings over 25 years of working knowledge in design, permitting, con-struction, and startup of mechanical, electrical, and instrumentation and controls projects as well as experience in the operation and maintenance of facilities.

LynnisaProfessionalEngineer,CertifiedEnergyManagerandhasaBSinNuclearEngineeringfromtheUniversityofTennessee.


Empowering Safety

NETA World, Winter 2005-2006 Issue

by Charlie SimpsonBurlington Electrical Testing Co.

Part 2 — From Gloves to Arc Flash Suits Employers Must Provide, Maintain and Ensure the Proper Use of their Employees’ PPE

According to theLibertyMutualResearch Institutefor Safety (www.libertymutual.com/research-institute-report2004),nearly3.5millionworkerssuffereddisablinginjuries in the workplace in 2003, costing businesses more than $190 billion in direct and indirect costs.

Employee safety is getting more attention than ever in the power distribution installation and maintenance industry. Personal Protective Equipment (PPE) helps provide the level of safety mandated by organizations such as OSHA and NFPA. Today the range of PPE can include primary and secondary insulation products, as well as equipment such as hot sticks, insulated hand tools, portable grounding cables and lockout/tagout systems.

Primary insulation, such as rubber gloves and rubber blankets normally insulate an employee directly from an energized part. Secondary insulation such as footwear and matting normally insulates an employee’s feet from a grounded surface (See New Laws Coming in Part 1 of the Fall issue of NETA World.)

Each employee should inspect his or her own PPE at the beginning of each work period and again before each use, while the company safety officer should establish a periodic review of all PPE.

One of the oldest, most reliable forms of PPE, and prob-ablymosttakenforgranted,istherubberglove.Glovesaremost susceptible to daily wear and tear damage; therefore, it is mandatory that employers collect and test gloves, as well as inspect leather gloves, carrying bags, etc.

Rubber gloves must be tested every six months. They may be tested and results documented in-house or sent out to be tested by an independent laboratory. OSHA also says rubber blankets and sleeves shall be tested every 12 months. Although there are currently no official standards for testing laboratories, employers can look for laboratory certification from an organization such as the Association

ofNorthAmericanIndependentLaboratories(NAIL)forprotective equipment testing, which conducts independent inspections and accreditation of testing laboratories.

Even if gloves are sent out for testing, employers can still maintain a glove log using an identification system for individual gloves which includes when they are tested and towhomtheywereissued.Glovesshouldbestoredoutofsunlight in the approved bag, and kept clean, which includes keeping bug repellents and lotions from coming in contact with the interior or exterior of the glove. Such products can break down the integrity of the rubber.

GlovetestingguidesandspecificationscanbefoundinOSHA1910.137.Glovesareratedinsixclassesaccordingfor use at a maximum voltage. Colored labels located near theglovecuffindicatethevoltageapplicationratingsuchas in Table 1.

Range Color Voltage 00 Beige 500 V 0 Red 1,000 V 1 White 7,500 V 2 Yellow 17,000V 3 Green 26,500V 4 Orange 36,000 V

Table 1 — Glove rating range and colors.

Even though there exists standards that allow for glove patching, most testing and certification experts will not repair gloves that fail his testing, insisting that replacement is the only action for ultimate safety. Hot sticks, on the other hand, may be refurbished to like-new condition, and can be tested and returned to service.


Figure 2 — Hot sticks may be refurbished to like new condition and must be tested annually

OSHA 1910.335(a)(1)(i) states that employers are re-sponsible for providing all appropriate equipment needed by the company and for the employees to do their jobs safely and in compliance with OSHA standards. Some choices seem simple: arc flash protection requires an arc flash suit. But what about everyday wear? Will a technician consistently wear the highest level of protection every time? Maybenot.Toaddressthisissue,fireresistant(FR)apparelmakers are designing lighter, more comfortable and flexible clothing,aswellasofferingmorevariety–fromHenleystyleshirts and hooded sweats to FR rainwear.

Today’s FR clothing is assigned a Hazard Risk Cat-egory (see Table 2), which corresponds to the arc thermal performance value (ATPV) and helps ease the employer’s evaluationofproperprotection.ATPVisdefinedinASTMF 1959-99 as one where there is a 50 percent chance of second degree burn with no under layers or for a breakopen. The idea behind the NFPA 70E Table is to use hazard/risk categories to help an employer choose the proper PPE for the corresponding application. Five categories defined in ASTMF1506-02ae1(Standard Performance Specification for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards) that range from 0 to 4 are used byASTMtoassignprotectivecategoriesforFRclothingbased on incident energy. This number should be clearly indicated on a garment.

OSHA 1910.269 for electrical worker’s apparel com-pliance means a worker’s clothing will not melt, ignite or continue to burn during an arc flash or fire exposure – a fire resistant garment can help satisfy this requirement. In 29CFR 1910.335 OSHA states that employees exposed to the hazard of arc flash shall wear PPE that is appropriate for the specific parts of the body to be

protected and for the work to be performed. The key word being appropriate, not too little, not too much.

FR garment providers suggest wearing enough clothing to ensure that the clothing absorbs as much of the arc’s en-ergy as possible – this is known as the garment’s Arc Rating. The heavier the fabric the higher the Arc Rating.

Hazard/Risk Category Clothing Description

Minimum Arc Rating of PPE cal/cm2 – ( J/cm2)

0 Nonmelting flammable materials – such as untreated cotton, rayon, silk, wool, or blend – of fabric weight at least 4.5 oz. (1 layer)

N/A

1 FR shirt and FR pant or FR cov-erall (1 layer)

4 (16.74)

2 Cotton underwear plus FR shirt and FR pant or FR coverall (1or 2 layers)

8 (33.47)

3 Cotton underwear plus FR shirt and FR pant or FR coverall; or cotton underwear plus 2 FR cover-alls (2 or 3 layers)

25 (104.6)

4 Cotton underwear plus FR shirt and FR pant plus multilayer flash suit (3 or more layers)

40 (167.40)

Table 2 — PPE Clothing Characteristics

The task of getting employees to wear bulky and inflexible garments while working in cramped or hot environments has never been easy A 65 cal/cm2 jacketmay offer thebest protection, but will be useless if it sits in the back of a technician’s truck on a 96-degree August day. So in addition to the required flash protection suits technicians must wear, you may decide another approach for everyday wear that offerstheprotectionand that you know an employee will consistently wear, and not unbutton or roll up the sleeves.

One method to increase FR protection, while maintain-ing flexibility, is through layering; for example, wearing a sweatshirt over a Henley. The air between the two shirts has been shown to provide an additional layer of protection, about 50 percent more protection than the sum of the two garments separately.

Cost, always a consideration must be gauged against the consequences.Maybeanemployerisnotinapositiontofully outfit every technician today. There are minimal levels to acquire – what those levels are will be up to an individual company’s analysis. But once you an employee is outfitted, say for $1,000.00, maintaining that level of protection could drop to $200.00 a year. Considering that a litigation settle-ment from one unprotected employee could equal the price of outfitting hundreds of employees for a lifetime, you may want to reprioritize the PPE budget.

Additionally, the employer is responsible to ensure clothing retains its flame retardant properties through conditions of use and laundering; therefore, it is important that employees understand about the care of FR clothing.


PPE AdvancementsEmployers should keep an eye out for advancements in

PPE to help ensure that employees will wear the appropriate apparel. For example:

1. Rubber gloves that are not rubber. Although not as flex-ibleasnaturalrubber,Dupont’sEPDMisasyntheticmaterial that is oil resistant, ozone resistant, and resists sun-checking.

2. Arc resistant and fire resistant rainwear is now avail-able.

3. Arc flash suits with small fans on the back are available. This increases comfort and reduces mask fogging.

Manufacturingadvancementsintheworksincludein-jected molded gloves that promise to provide more dexterity and comfort. Developers are also working with carbon-based fiberstoincreasethedurabilityofandprotectionofferedby garments.

Fortunately,accordingtotheBureauofLaborStatistics’data, overall worker safety, in general, has increased over the past ten years, including the electrical industry – from 548 electrical-related fatalities (out of a total 6,588 deaths) in 1994 to 353 electrical (out of a total 5,559) work-related fatalities in 2003. However, independent analysts estimate that there are more than 2,000 arc flash related burn injuries a year where there is greater than 50 percent second degree burns to the body. This number is far too many. The good news is that employers can reduce these numbers through the procurement and maintenance of employees’ PPE and instruction in its use.

Charlie Simpson is the Technical Writer for Burlington Electri-cal Testing Co. (BET, www.betest.com, Croydon, PA). BET, a NETA Accredited Company, is an independent electrical testing and main-tenance company servicing the industrial, commercial, construction, medical and utility industries for all manufacturers of power generation and distribution equipment in the low to EH voltages.

AcknowledgementsBET appreciates the contributions of Peter Senin, presi-

dentofBurlingtonSafetyLabsandKevinMcLaughlinofTyndale who contributed their expertise to this article, and thanks Jim White of Shermco for reviewing the accuracy of this article.

PhotocourtesyofBurlingtonSafetyLaboratory,Inc.

References1. The Maintenance & Testing of Rubber Goods, Burlington

SafetyLaboratory,Inc.2. NFPA 70E, Table 130.7(C)(11), Protective Clothing

Characteristics.

Some items are dry cleanable, but most are wash in cold or warm water and tumble dry; however, do not use fabric softeners or detergents with softeners as they can leave a residueonthegarment.Quitesimply,readthelabelsthatcome with the apparel.

After having conducted an arc flash analysis, determined the level of PPE and selected a style of PPE, it is just a matterofordering30XLs,15LsandoneortwoXXLsfor good measure. For some PPE that’s fine; however, the bestmethodistohavestaffmeasuredandfittested,fromgloves to arc flash suits. This will help ensure comfort and optimal performance, and that the PPE will be consistently worn by employees.

Before placing the order confirm PPE requirements with individual industries and their sites before purchasing PPE. For example, you may buy 30 Indura® FR shirts only to discover that the petrochemical industry insists on Nomex®. Youmayevenbesurprisedtodiscoverthatthemanagementof individual plants require only a specific color of material be worn on their site.

In addition to OSHA, the Occupational Safety and Health Act of 1970 created the National Institute for Oc-cupational Safety and Health (NIOSH). NIOSH, which dedicates its own laboratory, the National Personal Protec-tiveTechnologyLaboratory(NPPTL),toadvancingfederalresearch on PPE technologies, has investigated dozens of work-related electrocutions over the past decade (www.cdc.gov/niosh/injury/traumaelface.html).Manyofthemcitelack of or incorrect use of PPE, from no arc warning labels to wet gloves.

Their conclusions often recommend the lockout/tagout procedure for working with live or potentially live electrical systems. Employers must develop energy control procedures for shutting down, isolating, blocking and securing machines or equipment to control hazardous energy. The fundamental reason for having a lockout / tagout procedure is that there is a lock with one key for every person involved in any electrical systems operation.

Unlikealockout,atagoutprocedurealonemaynotin-clude physically locking out the switchgear. This could allow the switchgear to be placed in the remote position, thereby making it possible to operate and energize systems from outside the equipment room where technicians are working. While lockout procedures are not fail-safe, physically isolat-ing electrical components with locks, with keys controlled by the workers performing the work in the compartment, provides an additional level of protection, and, in most cases, is required by OSHA.

Finally, arc flash hazard warning labels can be considered asimple,yeteffective,formofPPE,indicatingthelevelofPPE needed and the arc flash and shock protection bound-aries. If the employee knows and understands the hazards and what is expected, the battle is half over when it comes to safe work practices.

NETA Accredited Companies

A&F Electrical Testing, Inc. ....................................................................Kevin ChiltonAdvanced Testing Systems ..................................................... D. Patrick MacCarthyAmerican Electrical Testing Co. ....................................................... Scott A. BlizardApparatus Testing and Engineering .................................................... James LawlerApplied Engineering Concepts ................................................ Michel CastonguayBurlington Electrical Testing Company, Inc. ......................................Walter ClearyC.E. Testing, Inc. ...............................................................................Mark ChapmanDYMAX Holdings, Inc. ..........................................................................Gene PhilippEastern High Voltage ......................................................................... Joseph WilsonElectric Power Systems, Inc. .....................................................................Steve ReedElectrical and Electronic Controls ..................................................Michael HughesElectrical Energy Experts, Inc. .............................................................William StyerElectrical Engineering Consulting & Testing, P.C. ........................ Barry W. TyndallElectrical Equipment Upgrading, Inc. ....................................................Kevin MillerElectrical Reliability Services .................................................................. Lee BighamElectrical Testing Services ..................................................................... Frank PlonkaElectrical Testing, Inc. ..............................................................................Steve DoddElemco Testing Co. Inc. .....................................................................Robert J. WhiteESCO Energy Services ........................................................................ Lynn HamrickHampton Tedder Technical Services ....................................................Matt TedderHarford Electrical Testing Co., Inc. ............................................... Vincent BiondinoHigh Energy Electrical Testing, Inc. .................................................James P. RatshinHigh Voltage Maintenance Corp. .........................................................Tom NationHMT, Inc. ................................................................................................ John PertgenIndustrial Electric Testing, Inc. ......................................................Gary BenzenbergIndustrial Electronics Group .................................................................. Butch E. TealInfra-Red Building and Power Service ...................................... Thomas McDonaldM&L Power Systems Maintenance, Inc. ...........................................Darshan Arora

To ensure quality — look for the NETA logo

The following is a listing of all NETA Accredited Companies as of June 4, 2009. Please visit the NETA website at www.netaworld.org for the most current list.


Magna Electric Corporation ................................................................... Kerry HeidMagna IV Engineering – Edmonton ..............................................Jereme WentzellMagna IV Engineering, Ltd. – BC ......................................................Cameron HiteMET Electrical Testing Co., Inc. .................................................. William McKenzieNationwide Electrical Testing, Inc. ........................................... Shashikant B. BagleNorth Central Electric, Inc. .............................................................. Robert MessinaNorthern Electrical Testing, Inc. ........................................................Lyle DettermanOrbis Engineering Field Services, Ltd. ................................................... Lorne GaraPhasor Engineering ..............................................................................Rafael CastroPotomac Testing, Inc. ................................................................................Ken BassettPower & Generation Testing, Inc. ........................................................Mose RamiehPower Engineering Services, Inc. ...................................................Miles R. EngelkePower Plus Engineering, Inc. ......................................................Salvatore MancusoPower Products & Solutions, Inc. ......................................................Ralph PattersonPower Services, Inc. ..........................................................................Gerald BydashPower Systems Testing Co. ............................................................... David HuffmanPower Test, Inc. ................................................................................. Richard WalkerPower Testing and Energization, Inc. ...............................................Chris ZavadlovPowertech Services, Inc. .................................................................... Jean A. BrownPRIT Service, Inc. ..........................................................................Roderic HagemanReuter & Hanney, Inc. ....................................................................... Michael ReuterREV Engineering, Ltd. .....................................................................Roland DavidsonScott Testing, Inc. .................................................................................. Russ SorbelloShermco Industries, Inc. ...........................................................................Ron WidupSigma Six Solutions, Inc. ..........................................................................John WhiteSouthwest Energy Systems LLC ......................................................Robert SheppardTaurus Power and Controls, Inc. ............................................................Rob BulfinchThree-C Electrical Company, Inc. ......................................................James CialdeaTony Demaria Electric, Inc. ...........................................................Anthony DemariaTrace Electrical Services & Testing LLC ................................................Joseph VastaUtilities Instrumentation Service, Inc. ......................................................Gary WallsUtility Service Corporation ..................................................................Alan Peterson

About the InterNational Electrical Testing Association

The InterNational Electrical Testing Association (NETA) is an accredited standards developer for the American National Standards Institute (ANSI) and defines the standards by which electrical equipment is deemed safe and reliable. NETA Certified Technicians conduct the tests that ensure this equipment meets the Association’s stringent specifica-tions. NETA is the leading source of specifications, procedures, testing, and requirements, not only for commissioning new equipment but for testing the reliability and performance of existing equipment.

CERTIFICATIONCertification of competency is particularly important in the electrical testing industry.

Inherent in the determination of the equipment’s serviceability is the prerequisite that individuals performing the tests be capable of conducting the tests in a safe manner and with complete knowledge of the hazards involved. They must also evaluate the test data and make an informed judgment on the continued serviceability, deterioration, or nonserviceability of the specific equipment. NETA, a nationally-recognized certification agency, provides recognition of four levels of competency within the electrical testing industry in accordance with ANSI/NETA ETT-2000 Standard for Certification of Electri-cal Testing Technicians.

QUALIFICATIONS OF THE TESTING ORGANIZATIONAn independent overview is the only method of determining the long-term usage

of electrical apparatus and its suitability for the intended purpose. NETA Accredited Companies best support the interest of the owner, as the objectivity and competency of the testing firm is as important as the competency of the individual technician. NETA Accredited Companies are part of an independent, third-party electrical testing associa-tion dedicated to setting world standards in electrical maintenance and acceptance testing. Hiring a NETA Accredited Company assures the customer that:

• TheNETATechnicianhasbroad-basedknowledge—thispersonistrainedtoinspect, test, maintain, and calibrate all types of electrical equipment in all types of industries.

• NETA Technicians meet stringent educational and experience requirements in accordance with ANSI/NETA ETT-2000 Standard for Certification of Electrical Testing Technicians.

• ARegisteredProfessionalEngineerwillreviewallengineeringreports.

• Alltestswillbeperformedobjectively,accordingtoNETAspecifications,usingcali-brated instruments traceable to the National Institute of Science and Technology (NIST).

• Thefirmisawell-established,full-serviceelectricaltestingbusiness.


neta handbook series i, arc-flash vol 1-pdf

Documents

custom vacuum interrupters

obsolete breakers

electrical equipment

shop replacement

facility local replacement

facility field replacement

medium voltage draw

arc flash protection