stray voltage
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Elevated Neutral to Earth and Metallic Objectto Earth Voltage Assessment Update Historical EPRI Research, 2005 2009
Strategic Roadmap and Future Research
Doug Dorr EPRI Solutions Inc.
Director Project Development
ddorr@eprisolutions.com
407-968-3010
February 17th
2006
22006 Electric Power Research Institute, Inc. All rights reserved.
Presentation Summary
Brief overview of past EPRI Stray Voltage research
A few examples induced voltagesand harmonicNEV
2005-2009 EPRI Stray Voltage Strategic Roadmap
2005 Completed Work
2006 Effort
Future Stray Voltage Work
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32006 Electric Power Research Institute, Inc. All rights reserved.
Questions and Concerns Fielded by the EPRISolutions Power Quality Hotline
Personnel safety concerns related to touch potentials
Animal contact area concerns related to health and productivity impacts
Residential water and gas pipe shocking concerns
Harmonic frequency voltages imposed on industrial gas lines
Power circuit resonance conditions creating elevated NEV levels
Shocking concerns with boat docks
Insulated metallic pipe corrosion concerns
Impacts of power line carrier communications technologies and othertransient generating devices on stray voltage magnitudes
Impacts of new gas and water line installations in power line right of ways
Induced voltages onto fences and light poles
Swimming pools and outdoor water faucets
Different opinions on measurement equipment specifications, measurementprotocols and measurement durations
42006 Electric Power Research Institute, Inc. All rights reserved.
EPRI Stray Voltage Research Roadmap
The prioritized research plan identified five areas ofopportunity where supplemental or new research wasneeded:
Test and measurement protocols
Modeling and simulation guidelines
Test equipment and mitigation methods
Technology transfer Informational website
Regulatory guidance (NEV and MOEV baselines andwhat voltage levels are not a concern)
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52006 Electric Power Research Institute, Inc. All rights reserved.
EPRI Program 128 Base Research ProjectObjectives and Solutions
The EPRI project provides information services andtargeted research related to elevated neutral to earthvoltage and metallic object to earth voltage concerns
2005 Informational website, measurement protocols
2006 Develop distribution system modeling andsimulation guidelines
2007 Testing on mitigation and measurement devicesand perform survey of NEV levels on distributionsystems
2008 09 Regulatory informational support, designbest practicesand other R&D as directed by theproject sponsors
62006 Electric Power Research Institute, Inc. All rights reserved.
Some Examples of Past EPRI Research
EPRI TR 114340 Stray Voltage Sensitivity Levels for Dairy, Swineand Poultry
EPRI TR 113566 Identifying Diagnosing and Resolving ResidentialShocking Concerns
EPRI EL-3106 V1, V2, V3, V4 This report series addresses complexcommon corridor coupling problems for overhead electric powertransmission lines and buried natural gas pipelines
Modeling and simulation results on the impact of automated meterreading technologies at animal contact points
Dozens of field investigations involving dairy farms, gas pipelines,swimming pools, hot tubs and other stray voltage sources
The first of its kind distribution wide NEV assessment model
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72006 Electric Power Research Institute, Inc. All rights reserved.
Some Examples of Past EPRI Research
The first successful installationof distribution system harmonicfilters to mitigate elevated NEVcaused by harmonicresonance
Client confidential researchinto pedestrian level UrbanStray Voltage concerns
White papers and technicalbriefs on topics related to strayvoltage
Workshops and seminars
Five Wire Distribution
Demonstration Project inUpstate NY
82006 Electric Power Research Institute, Inc. All rights reserved.
Example of Coupling to a Pipeline EL-3106
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Example Trending Correlation ofTransmission Loading (yellow) to NEV (red)
0.0
100.0
200.0
300.0
400.0
500.0
600.0
8/29/02 0:00 8/30/02 0:00 8/31/02 0:00 9/1/02 0:00 9/2/02 0:00 9/3/02 0:00 9/4/02 0:00
102006 Electric Power Research Institute, Inc. All rights reserved.
Example of Harmonic NEV Concerns
An EPRI member utility and EPRI Solutions have jointlyundertaken a research effort that involves modeling andsimulation of substations
The primary objective was to better understand the means ofreducing neutral-to-remote earth voltage (NEV) levels on theprimary power distribution circuits
The main considerations were to:
Replicate measured field data
Develop a way to assess NEV at any point on a distributioncircuit
Determine what effects, if any, parametric variations on theresistances, impedances and capacitances of thesubstations and their distribution circuits might have on theNEV levels
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112006 Electric Power Research Institute, Inc. All rights reserved.
60Hz Currents Cancel while Triplen HarmonicCurrents Add in the Return Path(s)
0
)120sin(
)120sin(
)sin(
=++=
+=
=
=
CBAN
cC
bB
aA
IIII
tII
tII
tII
CircuitPhaseThreeBalanced
[ ][ ]
)3sin(*3
)120(3sin
)120(3sin
)3sin(
33333
33
33
33
tIIIII
tII
tII
tII
LoadPhaseSinglewithCircuitBalanced
rdardCrdBrdArdN
rdcrdC
rdbrdB
rdardA
=++=
+=
=
=
From: L. Conrad et. al., Electric Shock and Elevated EMF Levels Due to Triplen HarmonicsIEEE Transactions on Power Delivery, Volume 11, No. 2, April 1996
122006 Electric Power Research Institute, Inc. All rights reserved.
Modeling and Simulation Overall
Objective
The system model and the dynamic simulations
Allows for simulation and analysis of NEV levels and neutral currentsalong the distribution system under several types of utility, systemconditions, or grounding.
Enables a better way to understand how different electrical parametersimpact the level of NEV and currents at points of interest during differentutility load conditions (summer as well as winter)
The results of this modeling effort enable a betterunderstanding of the methods that can be used to reduceNEV levels at customer connection points
The results will allow for accurate estimates of the NEV levelsthat can be expected during both winter and summerconditions and provide a way to compare solutions form botha cost and a relative improvement perspective
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132006 Electric Power Research Institute, Inc. All rights reserved.
Modeling and Simulation What parameterswere varied or evaluated in the models?
Neutral conductors
Sizing and parallel configuration Neutral conductorimpedance is a parameter that impacts the percentage ofreturn currents that flow into the earth at N/G bondingpoints
Grounding
Resistance of the substation grid The resistance of theground grid is in parallel with every other pole ground onthe power system and in series with the current paththrough the earth back to the transformer XO bushing
Resistance of the circuit pole grounds Every N/G bondon the power system has a measurable NEV with respectto remote earth as well as an equivalent resistance inparallel with the cable, telco and customer grounds
142006 Electric Power Research Institute, Inc. All rights reserved.
Modeling and Simulation What parameters
were varied or evaluated in the models?
Capacitor Banks
Grounded versus ungrounded grounded cap banksmay increase the amount of NEV a parallel resonancecondition is present
Circuit Loading
Winter loading vs summer loading During peakloading conditions, more current will typically yieldhigher NEV levels even if the earth resistance does not
change (V = R x I)Harmonic filter configurations
Single circuit versus multi-circuit filters Harmonicfilters are a new method of dealing with NEV whentriplen harmonic currents are present
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152006 Electric Power Research Institute, Inc. All rights reserved.
Modeling and Simulation What parameterswere not varied or evaluated in the models?
Distribution circuit voltage levels
Lower voltage circuits have higher currents and NEVlevels
Load Balance Opportunities
Balanced 60Hz currents cancel on the neutral
Corroded (high impedance neutral connections)
Future connection issues may impact NEV levels
Individual residence impacts
NEV was evaluated at the pole down ground
Voltages induced onto metallic pipelines Gas and water lines can contribute to stray voltage
Infinite combinations of harmonic filters (36 factorial)
162006 Electric Power Research Institute, Inc. All rights reserved.
Substation Ground Grid Variation Example
Base Case Versus Substation Grid Variation Circuit 82 Branch 2(Summer and Winter)
6.4
1.8
1.3
0.5 0.5 0.7
9.8
2.7
2.0
0.8 0.81.1
6.0
1.7
9.1
2.6
1.9
0
2
4
6
8
10
12
160 ft (Subs tation
Riser)
1135 ft (Spiral and
Driscoll)
1405 ft (Spiral and
Azalea)
3340 ft (16th and
Burnt Tavern)
4500 ft (16th and
South Lake J C7)
5500 ft (20th and
South Lake BT5910)
Location
NEV(RMSVolts)
Winter Base Condition
Summer Base Condition
Winter Sub Grid Variation
Summer Sub Grid Variation
1 mile from sub
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25% Reduction in Pole Ground Resistance
Base Case Versus Ground Rods Variation Circuit 82 Branch 2(Summer and Winter)
6.4
1.8
1.3
0.5 0.5 0.7
9.8
2.7
2.0
0.8 0.81.1
5.8
1.4
8.8
2.1
1.4
0
2
4
6
8
10
12
160 ft(Substation
Riser)
1135 ft (Spiral and
Driscoll)
1405 ft (Spiral and
Azalea)
3340 ft (16th and
Burnt Tavern)
4500 ft (16th and
South Lake J C7)
5500 ft (20th and
South Lake BT5910)
Location
NEV(RMSVolts)
Winter Base Condition
Summer Base Condition
Winter Ground Rods Var
Summer Ground Rods Var
1 mile from sub
182006 Electric Power Research Institute, Inc. All rights reserved.
Design consists of 3 capacitors connected in wye with aneutral reactor tuned to, or near, the 3rd harmonic
Filter Schematic and Physical Photograph
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192006 Electric Power Research Institute, Inc. All rights reserved.
Summer Variation
Circuit 82: Circuit Going toward 16th and Burnt Tavern (Branch 2)
9.82
2.75
1.99
0.82 0.84 1.07
20.38
4.06
1.96
1.340.84 1.02
10.49
2.99
2.23
0.99 0.82 1.06
4.07
1.721.27
0.94 0.821.06
0
3
6
9
12
15
18
21
24
160ft(SubstationRiser)
1135ft(SpiralandDriscoll)
1405ft(SpiralandAzalea)
3340ft(16thandBurnt
Tavern)
4500ft(16thandSouthLake
JC7)
5500ft(20thandSouthLake
BT5910)
NEV
Base Case
Gnd. Cap Variations
UnGnd. Cap Variations
UNGnd. Cap & filteratJ C2248BK (83) & at J C228BKR44 (81) & atJ C195BKT146(82) & JC3211BK (80)
1 mile from sub
Parametric Variations on One Circuit
202006 Electric Power Research Institute, Inc. All rights reserved.
Modeling Issues Identif ied and Resolved
Individual CircuitModeling Versus Combined CircuitModeling
Neutral Interconnects
Capacitor variations
Filter variations
Neutral variations
Substation ground variations
Representing Ground Rods (Utility Ground, Aggregate grounds to reflectCATV, Telephone, and Residential Dwelling grounds) along the DistributionCircuits
Representing Substation Ground Resistance
Linear and Non-Linear Load Representation Capturing distributed effects of capacitors, filters, etc. usinga reduced
distribution modelversus a combined distribution model
Matching Phase and Neutral currents to Measured Values at different pointson the main line
Difference between measurement times at lateral connections
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Generic NEV (and MOEV) EvaluationPriorities
Adequate call handling and response procedures
Safe and accurate measurement protocols
Adequate instrumentation and personnel training
Consistent documentation for reporting and analysis
Understanding of all the possible causes
A procedure for peeling the onionstart with allpossibilities and systematically narrowing down the list
Preventive maintenance and spot monitoring
Design guidelines
222006 Electric Power Research Institute, Inc. All rights reserved.
NEV Mitigation Priorit ies
Individual Customer Bonding/Grounding/Isolation
Load Balancing (10 percent? 5 percent?)
Neutral Impedance Assessment
Harmonic Resonance Assessment
Ungrounded Capacitors
Tuned Harmonic Filters
Neutral Impedance Reduction
Grounding Assessment
Earth Resistivity?
Average Ground Rod Resistance
Aggregate Services and Customer Ground Resistance
Substation Ground Grid Resistance
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EPRI 2005 Base Project 128.003
Assessment of Metal lic Object and ElevatedNeutral-to-Earth Voltages in Distribut ionSystems
Objectives: Refine existing measurement protocols and get
consensus on consistent repeatable investigation andassessment methodologies for the ranges of concernsincluding Pipelines, Swimming pools, Distribution systemNEV concern points and Street level metallic objects
Enhance the the case study database developed in the2004 EPRI Elevated NEV TC project to includeadditional areas of interest such as telephone
interference, gas and water pipeline induced voltages,rail lines and non-canceling harmonic currents Host NEV and MOEV website
242006 Electric Power Research Institute, Inc. All rights reserved.
Technical Update Report is Available
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Technical Update Report is Available
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Section 1
Details the EPRI Stray Voltage Multi-Year Plan
Describes the need for a comprehensivemeasurement
protocol document to cover all areas of interest (Residential,Animal Contact, Urban Stray Voltage)
Provides definitions that will be useful to the IEEE workinggroup on stray voltage in their efforts (NEV, MOEV, StrayVoltage etc
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Section 2
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Measurement Section Focuses on the
Consensus Recommended Practice
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Measurement Section Details the Equipment and Other Considerations used in the Assessment
Use of trending versus snapshot for time of days andsource correlations
Harmonics and the importance of understanding thespectral content of the NEV
Pen Lights
Hand Held Meters
Data Loggers
Multi Channel Recorders
302006 Electric Power Research Institute, Inc. All rights reserved.
Section 3
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Section 3
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Section 4
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Section 4
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Section 5
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Section 5
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Section 6
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Section 6
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Section 7
Chapter Concept: Develop a simple means of
checking your equipment anddocumenting its accuracy beforedoing any for the recordtesting
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128.003 Deliverable: Stray Voltage Website
On-Line since J uly 2005http://strayvoltage.epri-peac.com
402006 Electric Power Research Institute, Inc. All rights reserved.
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IEEE Working Group Update
The Stray Voltage working group (WG) is a newly formed group under thedistribution subcommittee of the IEEE Power Engineering Society Transmission and Distribution Committee.
Website URL - http://grouper.ieee.org/groups/straywg The working group PAR (project authorization request) has been submitted
and should be approved in the first quarter of 2006. The scope of the PAR is to develop an IEEE guide related to stray voltage
that will potentially cover; definitions, measurement protocols andequipment, mitigation techniques, as well as proposed levels of non-concern
The WG met in January and finalized the PAR and reviewed a set ofdefinitions supplied by a task force under the working group
The WG is sponsoring a panel session at the May 21-24 T&D show inDallas. Title: Stray VoltageCauses, Impacts and Mitigation PN27 -Wednesday, May 24, 10:00 am-12:00 pm
The next meeting of the WG will be at the IEEE PES Summer Powermeeting in Montreal in J une 2006 (meeting date and time TBD. For moreinformation contact secretary: russ.ehrlich@.conectiv.com
422006 Electric Power Research Institute, Inc. All rights reserved.
EPRI Stray Voltage Research Roadmap
The prioritized research plan identified five areas ofopportunity where supplemental or new research wasneeded:
Test and measurement protocols
Modeling and simulation guidelines
Test equipment and mitigation methods
Technology transfer Informational website
Regulatory guidance (NEV and MOEV baselines andwhat voltage levels are not a concern)
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432006 Electric Power Research Institute, Inc. All rights reserved.
2006-2009 Preliminary ResearchRecommendations
This project continues to provide information services andresearch results related to elevated neutral to earthvoltage and metallic object to earth voltage concerns
2006 Develop distribution system modeling andsimulation guidelines
2007 Testing on mitigation and measurement devicesand perform survey of NEV levels on distributionsystems
2007 09 Regulatory informational support and otherR&D as directed by the project sponsors
442006 Electric Power Research Institute, Inc. All rights reserved.
2006 Assessment of Elevated Neutral-to-Earth
Voltages in Distribution Systems
Project Objectives and Solutions
Develop best practices for Modeling and Simulation.
Initiate industry association dialog to assist with emerging designpractices for bonding and grounding.
Support IEEE activities to develop proposed regulatory guidelinesfor establishing levels of concern for elevated neutral and metallicobject to earth measured values
Continue to add support material to update the NEV and UrbanStray Voltage Website
Increase the number and range of examples in the case studydatabase developed in 2004 and 2005 to include additional areas ofinterest such as telephone interference, gas and water pipelineinduced voltages, rail lines and non-canceling harmonic currents
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452006 Electric Power Research Institute, Inc. All rights reserved.
2006 Modeling and Simulation Approach
A main goal in 2006 is to implement lessons learned from modeling andsimulation studies to enable more efficient ways to model NEV acrossdistribution systems
Representation of aggregate ground resistance values
Understanding of how ground currents and the corresponding NEV canbe calculated in the circuit models
Understanding how physical placement of neutral conductors caninfluence NEV levels
This information will be the basis of modeling guidelines to potentiallyprovide design objectives for new transmission segments, new substationsand mitigation options for existing substations
462006 Electric Power Research Institute, Inc. All rights reserved.
Questions this Project Should Resolve
Can simplified circuit models be used to accurately assess NEVlevels across many miles of distribution circuits
How do you accurately represent pole grounds rod in parallel withthe telephone, cable, and customer service ground rods
When the ground rods are paralleled, how do you determine theactual NEV value for a given pole ground?
What potential impacts do distributed capacitor banks and groundingof those banks have on NEV levels
How do you represent harmonic loads from customers
What field measurements are required to confirm model results
What equipment and protocols are required to insure field data istaken accurately
What level of accuracy in terms of matching model results to fieldresults is considered acceptable?
How do you represent substation ground grid resistance in themodel
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Conclusions
The EPRI Research Plan is aligned with the strayvoltage roadmap described on the website at:http://strayvoltage.epri-peac.com
The initiatives surrounding the Elevated Neutral to Earthand Metallic Object to Earth Impacts and Controlsproject are intended to supplement not repeatanyprevious or ongoing efforts
The information repository on the website and the
informational hotline are intended to bring support andtechnical expertise to personnel investigating elevatedvoltage concerns
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