Advanced Protection Technologies

ITS Surge Protection Training

2014

Performed by: Pete Ganci, BSET

Sales Engineer

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Agenda - Surge Suppression

Outline:

1. Basics

2. Applying/Installing AC SPDs

3. Applying/Installing

Comm/Data/Coax SPDs

4. Grounding & Bonding

5. Case Study

6. APT Products

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What Is a Surge/Transient? • High amplitude, short duration overvoltage

• Can be positive or negative polarity

• Can be from energized or grounded conductor

Transient Overvoltage – Can be thousands of volts

Millionths of second

Surge Protectors

„Chop Out‟ surges

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What Causes Surges/Transients?

• Lightning

• Switching:

– Load Switching – utility & customer

• Motors, Large Loads, Faults,

Fuse Operation

– Source Switching

• Smart Grid, Gensets, PV, Wind

Turbine

• Internally generated surges: ≈70%

• Externally generated surges: ≈30%

In outdoor environment,

this ratio probably reverses

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SPD Terminology • Let-through voltage, suppressed voltage, measured

limiting voltage (measured in Vpeak) clamping voltage?

• Surge current, peak-amp current, maximum current,

(measured in Apeak)

• MCOV - Maximum Continuous Operating Voltage of the

electrical system (measured in Vrms)

Load

Surge Current

(thru SPD)

MOV/SPD

Let-Through

Voltage

MCOV

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MOV - Metal Oxide Varistor • Varistor - variable resistor

• Semiconductor; generally zinc oxide

• Thickness determines clamping voltage

• Diameter determines current capacity

• Overvoltage diverts through MOV as current

• Voltage is “clamped” or “equalized” as energy is transferred to other side of MOV(s)

• MOV does not „absorb‟ surge, however, I2R heat is retained

• Bidirectional – Operates same for positive or negative surges

• Creates a momentary short-circuit to pass transient energy to earth; analogous to water heater pressure relief valve

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Load

Series

Basic Suppressor Layouts:

Series & Parallel

Advantages • Inductive Filter - denies the instantaneous change in

current, prohibiting the propagation of transients

• Improves SPD Let Through Voltage

Concerns • Not Bi-directional

• Potential loss of Power/Signal upon failure

• Servicing requires de-energizing system

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Basic Suppressor Layouts:

Series & Parallel

Load

Parallel MOV/SPD

Advantages • Advanced Suppression Componentry - TPMOV

• Bi-directional Operation

• Can be serviced without de-energizing entire system

Concerns • Lead Lengths effect performance

• Higher Let Through Voltages compared to Series Filters

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SPD Operation

MOV/SPD Acts as a momentary „short circuit‟

„short circuit‟ ≈ no overvoltage ≈ protected load

Load 1 Load 2

Load 3 Load 4

Load 5

(Good thing that will never happen to me… )

Can Anything Go Wrong?

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SPD/MOV Failures • MOV is a sacrificial element

• Failure caused by:

– Sustained Overvoltage – TOV (Maybe as few as 2-3 cycles)

– Sequence: MOV protects, fails, fails short, follow-on fault current causes MOV to catastrophically overheat

• MOVs are Variable Resistors

• MOVs fail toward short, but not necessarily hard short

• Failed MOV impedance can vary from 200 - 0

• No clearing curves, can‟t field-determine OCP or thermal protection

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Typical Sequence of MOV Failure

Load

MOV/SPD

System level Sustained Overvoltage – TOV Voltage exceeds MCOV – as little as 2-3 cycles

MOV attempts to protect

MOV fails towards short circuit

Follow-on/fault current causes MOV to catastrophically overheat

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Load

MOV/SPD

Current

„Lower‟ Fault

Currents (0-20A)

„Intermediate‟ Fault

Currents (20-1000A)

„Higher‟ Fault

Currents (>1000A)

Tim

e

MOV Failure Intensity Increases With The

Amount of Fault Current Drawn by the MOV

Safety, UL 1449-3 & NEC

SPD

TVSS Surge

Arresters

SPDs/TVSS arguably the most regulated electrical

product category in the 2000‟s • UL 1449-2 (Aug 1998)

• 2002 NEC Article 285

• 2005 NEC Article 285

• UL 1449-2.5 (Feb 2007)

• 2008 NEC Article 285

• UL 1449-3 (Sept 2009)

• 2011 NEC Article 285

Safety evolved quickly as the body of knowledge grew

• UL 1449 Plays Huge Role in Surge Industry

• Much More Than a Safety Standard

• Perform Multiple Performance Tests

• UL uses for internal UL 96A Lightning Protection Master Label Eval

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Thermally Protected MOV

• Large 34 mm sq. MOV

• TPMOV optimizes thermal protection to double-function as overcurrent protection

• How a TPMOV works

– Under normal conditions TPMOV conducts surges as any other MOV would

– During a sustained overvoltage the MOV attempts to control, it fails, follow on fault current causes the MOV to heat up

– As the MOV heats up the solder will melt releasing the tension loaded latch disconnecting the failed MOV

– As a secondary measure the spring loaded arc shield extinguishes any reaming arc

Thermally Protected MOV

• TPMOV Advantages: – Robust distribution grade MOVs

– Each MOV is individually fused

– Each MOV integrally fused

– Eliminates external breaker/fusing coordination issues

– One homogenous unit creates very efficient clearing of failed MOVs

– Robotized assembly minimizes tolerances between fuses, MOVs, and thermals

– TAC switch allows for individual monitoring of each MOV

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II.) Applying/Installing AC

SPDs

• ITS/DOT Surge Environment

• Modes of Protection

• Inductance and Surges

• Installing AC SPDs

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SPD Types: Types 1, 2, 3 & 4 Based on Location within electrical distribution system

(coincides with ANSI/IEEE C62.41.2-2002 Categories C, B & A)

UL 1449-3 & NEC Art 285

Trans

Meter

Svc.

Disc.

Panel

Type 1

10m (30feet)

Type 2

Type 3 (Plug-In)

OCP built in to

SPD, more

rigorous testing

Type 4 (Component) tested to Type 1 or Type 2

Cat A (500A)

Cat B (3kA) Cat C (10kA)

UL &

NEC

Types

IEEE

Cats

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Lightning strike to earth-grounded pole

raises Ground Potential, also causing

Transient Overvoltage

Surge or

Transient

Overvoltage

Transient overvoltages are not limited to utility or power

conductors

An Instantaneous Ground Potential Change is Also a

Surge

Surges in DOT Environments

On Power

Conductor

On Ground

Conductor

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DOT is a unique situation

S.E. USA transient environment is one of the worst

ITS/DOT environment is worse than IEEE portrays because IEEE

focuses on surges entering on power lines, not coming from

ground

Pole or high-mounted makes things worse

Big Problem is that the power system references ground a long

way away from pole ground. On a direct strike, the pole goes up

thousands of volts relative to the power system.

Wind Turbine environment is similarly problematic (but they have

more expensive equipment, costlier downtime, spend more money

on surge & grounding, and still have massive problems)

Surges in DOT Environments

Amber Alert

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Trans

Meter

Svc.

Disc.

Cabinet

10m (30feet)

Cat C – 10kA

Cat A – 0.5kA

Traffic Applications Are Different Due to Multiple Threats:

Surge To Service Entrance:

1.) Surge Hits Power/Line

2.) Traditional Building?

3.) Inductance Limits Propagation

4.) IEEE C62.41 Categories C, B & A (enter for animation 1)

Cat B – 3kA

Surge Near Load:

1.) Surge Hits Ground/Grounded Equip.

2.) Elevated NON-Traditional Structure

3.) Inductance Limits Propagation

4.) IEEE C62.41 Categories C, B & A? (enter for animation 2)

??Cat C – 10kA?? Cat B – 3kA?

Takeaways:

• Multiple Threats

• Plenty of Unknowns!

• Need Additional

Modes of Protection

Pole Ground Power System Ground

How Much to

Ground?

How Much to

Power Lines?

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Modes of Protection

• Different ways to configure protection within SPDs

• MOVs equalize potential

across either side of MOV

• Various ways to connect MOVs – L-N

– L-G

– N-G

– L-L

A-N

A-G

Phase A

N

Ground

Earthed

Transformer

Impedance

SPD

Different Modes of Protection: Service Scenario Assumes (Split Phase): 1.) Surge Is From Outside

2.) SPD near Service Entrance or Separately Derived System

3.) Propagation, Return Paths and Ground are Ideal

4.) SPD chops off surge and sends it to Ground

(Enter for Animation)

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Phase A

Neutral

Ground

SPD

N-G C-G

A-G

1.) Surge Is From Outside to Ground or Grounded Enclosure or Pole

2.) Surge might go towards Ground, but inductance will limit

propagation. And/Or, there will be Ground Potential Rise. This

will have the effect of „trapping‟ the surge near the load

3.) SPD will equalize potentials among Phases, Neutral and Ground

(Enter for Animation)

Assumes L-N, L-G and N-G protection

SPDs without these modes of protection will not be able to

protect as well. (Gee, I had an SPD, but still lost my equipment.)

Different Modes of Protection:

Downstream or Outdoor (Split Phase)

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SPD

C-N

A-N

Same slide as last, but with SPD having L-N protection only.

This shows what happens with insufficient modes of protection

(Enter for Animation)

Different Modes of Protection:

Downstream or Outdoor (Split Phase)

Surge Energy

Becomes Trapped

SPD‟s A-N and C-N protection are not

connected to Ground. Cannot do

anything with a surge from Ground.

Less Likely: Dielectric strength of

widget prevents arc-over

More Likely: Flashes-over and

destroys widget Phase A

Neutral

Ground

Ground

Different Modes of Protection (Split Phase) (Enter for Animation)

• Can create L-G and N-G voltage differences

• L-N, L-G and N-G protection are suggested

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The Pin represents the system‟s Neutral Bonding to Ground -

Fixed ground reference. L-N protection is the same as L-G.

Downstream, the system can „flex‟ from load imbalance, ground

faults, etc.

L-G and N-G protection are generally suggested in downstream

locations.

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Inductance & Surges

• Inductance: Electrical Property Whereby Instantaneous Current Changes Are Opposed

• Wire‟s inductance at surge frequencies is good and bad

• Inductance of wire is about 0.75μH/m (very low)

• Good because large surges cannot propagate far – Lightning generally effects very localized area, not large areas

• Bad because of effects on SPD installation – Long leads hurt SPD performance – Need Short SPD Leads

• Also bad on ground grids because the same physics apply. The inductance preventing widespread propagation also prevents dissipating that surge to ground.

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MOV/SPD Acts as a

momentary „short circuit‟

„short circuit‟ ≈ no overvoltage

≈ protected load

Load 1 Load 2

Load 3 Load 4

Load 5

SPD & Inductive Effects L (inductance)

limits

propagation of

lightning (good)

L (inductance) causes voltage

drop across conductor (bad –

need short leads)

Industry typically states: Each foot of

conductor adds 100 - 170V to clamping

voltage

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Power or low

voltage lines Creates Transient Voltage

Difference I.e., Surge – could be

1,000‟s of volts

Surge

• Anything & Everything separated by

Distance can be Affected

• One reason to install data SPDs at

both ends of conductor

Trans

Meter

Different References to Ground are Affected by

Ground Potential Rise - GPR

Outdoor, Pole, Tower or

„Backdoor‟ Surges

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• Application

• UL 497

• Common Configurations

• Installing Comm/Data SPDs

• Coax SPDs

• Coax: Cascading

• Coax: Avoiding Ground Loops

III.) Applying/Installing

Comm/Data/Coax SPDs

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Application of Comm, Data & Coax

• In low voltage applications other SPD building block technologies work better than MOVs

• MOV suppression components may degrade signal quality due to higher capacitance

• SPDs at both ends of the signal make sense

• In coax applications, the pin is protected by the shield – Emphasis protection on the pin is

misguided

• IEEE research shows 4x more surge current propagates on the shield than the pin (more to come)

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UL 497 Series - Comm, Data & Coax SPDs

UL 497: Primary Protectors for Communications Circuits (CCN: QVGV) “These protectors are intended to suppress abnormal voltage conditions that may exist on the circuit due

to accidental contact with electric light or power conductors operating at or over 300 V to ground as defined in the NEC. These devices may also be used to protect against electrical transients from an electromagnetic disturbance or higher than normal voltages induced on the communication circuits due to close proximity of the protected circuit to electric light or power conductors.”

UL 497A: Secondary Protectors for Communications Circuits (CCN: QVRG) “These protectors are intended to suppress abnormal voltage and/or current conditions that bypass the

primary protector. These devices limit currents to less than the current-carrying capacity of Listed communication wire employed in the communication loop of the protected premise. Any overvoltage protection and/or grounding connection is intended to be electrically located on the equipment side of the protector's current-limiting means.” “Secondary protectors are intended to be used in the protected side of telecommunications networks that have an operating rms voltage to ground less than 150 volts.”

UL 497B: Isolated Loop Circuit Protectors - Protectors for Data Communications and Fire-Alarm Circuits (CCN: QVGQ)

“These protectors are intended as suppression devices for abnormal voltage conditions that may exist on the circuit due to electrical transients from an electromagnetic disturbance. These protectors are not intended for use on circuits exposed to accidental contact with electric light or power conductors operating at over 300 V to ground.”

UL 497C: Primary Protectors for Coaxial Communications Circuits (CCN: QVKC) “The primary coaxial protectors are intended to suppress abnormal voltage conditions that may exist on

the circuit due to accidental contact with electric light or power conductors operating at over 300 V to ground as defined in Articles 800 and 830 of the NEC. These protectors may also be used to protect against electrical transients produced from electromagnetic disturbance on the communication circuits.”

Read the Scopes: Primary & Secondary Protectors

offer Very Different Protection

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Coax SPDs: Concept of

Cascade Protection

• UL 497 Listing Categories are often misunderstood – Primary Protectors: intended more for life safety

protection from power line crosses & lightning, may not clamp low enough to protect sensitive electronics

– Secondary Protectors: offers better clamping for sensitive electronics

• Single SPDs having both properties exist

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Load

Load

Series

Parallel

MOV

Comm, Data & Coax SPDs Componentry Operation & Configurations:

Common (Ground)

Common (Ground)

Series Connected:

Element Hiccup/Shortcoming

Inductor Traps on either side

Limits current, not voltage

Resistor Barely effective

Coaxial GDT GDT overshoot

Parallel Connected: Element Hiccup/Shortcoming

GDT Voltage overshoot

MOV Capacitance tends to swamp signal

SAD Small Capacity

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Comm, Data & Coax SPDs Typical ‘Better’ Three-Stage SPD Configuration:

L

GDT SAD Unprotected

Side Protected

Side

Normal Operation:

Common (Ground)

Load

L

GDT SAD Unprotected

Side

Protected

Side

Surge Operation:

High Frequency

Impedance such as

Inductance

Common (Ground)

Load

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Installing Comm/Data SPDs

• As a generalization if the distance between signal ends is greater than 15 feet an SPD should be installed at both ends of the signal – Prevents surges induced into the middle of the

conductor from damaging equipment at either end

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Coax SPDs: Avoiding Ground

Loops

• Coax shields are grounded at their „head-end‟, the shield is not supposed to be grounded downstream – Reason: grounded at multiple locations equals different

ground potentials and currents will loop through the shield as ground potentials attempt to equalize

• SPDs with ground isolation is required with separate pin-shield and shield-ground protection

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V.) Case Study

• Courtney Campbell Causeway in Tampa

• SPDee units installed for almost a year

• No failures of SPDs or ITS equipment

• Recently started adding the Data suppressors

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Project Overview

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Photos: AC Power

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Photos: Data