stray voltage

7/29/2019 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

[email protected]

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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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


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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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


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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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


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


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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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


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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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


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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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)


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


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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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


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


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


Technical Update Report is Available


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Technical Update Report is Available


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


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


Section 3


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Section 3


Section 4


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Section 4


Section 5


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Section 5


Section 6


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Section 6


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



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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: [email protected]


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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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


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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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


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

Documents

stray voltage