Trial Use Guide For Assessing Voltages At Publicly and Privately Accessible Locations (P1695) Section 6 Contact Voltage Scott Kruse Power Survey Company.

Trial Use Guide For Trial Use Guide For Assessing Voltages At Assessing Voltages At Publicly and Privately Publicly and Privately

Accessible Locations (P1695)Accessible Locations (P1695)Section 6 Contact VoltageSection 6 Contact Voltage

Scott KruseScott Kruse

Power Survey CompanyPower Survey Company

[email protected]@powersurveyco.com

973-634-7268973-634-7268

January 12, 2009January 12, 2009

David KalokitisDavid KalokitisPower Survey CompanyPower Survey Company

[email protected]@powersurveyco.com 973-986-5448973-986-5448

22

Presentation OverviewPresentation Overview

• Objectives Objectives

• Time Frame Time Frame

• Description of effort to dateDescription of effort to date

• Outline of draft textOutline of draft text

• FeedbackFeedback

• DiscussionDiscussion

33

ObjectivesObjectives• Distribution of Section 6 Contact Voltage to all Distribution of Section 6 Contact Voltage to all

group members through e-mail.group members through e-mail.• Post on Working Group website Post on Working Group website

http://grouper.ieee.org/groups/td/dist/stray/http://grouper.ieee.org/groups/td/dist/stray/• All interested parties to read and provide All interested parties to read and provide

feedback by sending word doc. with tracked feedback by sending word doc. with tracked changes and / or comments.changes and / or comments.

• Submit feedback to:Submit feedback to:Dave Kalokitis: Dave Kalokitis: [email protected]@powersurveyco.comScott Kruse: Scott Kruse: [email protected]@powersurveyco.comChuck DeNardo: Chuck DeNardo: [email protected]@we-energies.com

44

Time FrameTime Frame

• Submit any edited text or comments by the Submit any edited text or comments by the end of April for inclusion into the next end of April for inclusion into the next revision of the document. revision of the document.

Effort to dateEffort to date• A small number of contributors have A small number of contributors have

generated and mutually reviewed draftgenerated and mutually reviewed draft

• 22 pages22 pages

• Many openings for needed contributionsMany openings for needed contributions

55

6.1 Contact Voltage6.1 Contact Voltage

• DefinitionDefinition

• General Concerns General Concerns

• Shock HazardShock Hazard

• Shock TriangleShock TriangleH

uman

/Ani

mal

Energized S

urface

Ground

Shock

Hum

an/A

nim

al

Energized S

urface

Ground

Shock

66

6.1.1 Contact Voltage 6.1.1 Contact Voltage DiscoveryDiscovery

• Incident• Shock Report from Public / Other

• Inspection• Scheduled inspection and test of assets

• Detection• Manual Survey of Assets• Mobile Detection of Energized Surfaces

Energized Surfaces are often discovered by:

77

6.2.1 Contact Voltage Root 6.2.1 Contact Voltage Root CausesCauses

• Insulation DegradationInsulation Degradation• Failure of insulating materials Failure of insulating materials

• Neutral Corrosion / Burn OutNeutral Corrosion / Burn Out• Current may return through groundCurrent may return through ground• Neutral to earth voltage (NEV) due to resistanceNeutral to earth voltage (NEV) due to resistance

• WorkmanshipWorkmanship• Reversed polarityReversed polarity• Improper insulation of connectionsImproper insulation of connections

• Construction DamageConstruction Damage• Excavation, Road work, Improper Repair of DamageExcavation, Road work, Improper Repair of Damage

88

6.2.2 Energized Structures6.2.2 Energized Structures

• Manhole CoversManhole Covers

• Hand Hole CoversHand Hole Covers

• Street LightsStreet Lights

• Traffic SignalsTraffic Signals

• Sidewalk / RoadwaysSidewalk / Roadways

• Gates / FencesGates / Fences

99

6.3.1 Test and Measurement 6.3.1 Test and Measurement EquipmentEquipment

• 6.3.1.1 Hand Held Detector6.3.1.1 Hand Held Detector

• 6.3.1.2 Mobile E-field Detector6.3.1.2 Mobile E-field Detector

• 6.3.1.3 Hand Held E-field Detector6.3.1.3 Hand Held E-field Detector

• 6.3.1.4 Voltmeter6.3.1.4 Voltmeter

• 6.3.1.5 Ground Lead6.3.1.5 Ground Lead

• 6.3.1.6 Switchable Shunt Resistor6.3.1.6 Switchable Shunt Resistor

• 6.3.1.7 Ground Rod6.3.1.7 Ground Rod

• 6.3.2 Safety Equipment6.3.2 Safety Equipment

1010

6.3.4 Locating, Measuring and 6.3.4 Locating, Measuring and Mitigating Contact VoltageMitigating Contact Voltage

• 6.3.4.1 Discovery Methods6.3.4.1 Discovery Methods• 6.3.4.1.1 Incident6.3.4.1.1 Incident

• Record Keeping, CommunicationRecord Keeping, Communication

• 6.3.4.1.2 Inspection6.3.4.1.2 Inspection• Prescribed cyclic inspection of assetsPrescribed cyclic inspection of assets

• Record KeepingRecord Keeping

• 6.3.4.1.3 Detection – Underground/Overhead6.3.4.1.3 Detection – Underground/Overhead• 6.3.4.1.3.1 Manual Survey6.3.4.1.3.1 Manual Survey

• 6.3.4.1.3.2 Mobile Detection6.3.4.1.3.2 Mobile Detection

1111

6.3.4.2 Measurements6.3.4.2 Measurements

• What is the voltage level on the What is the voltage level on the energized surface?energized surface?

• Is the voltage supplied through low or Is the voltage supplied through low or high impedance?high impedance?

• How much current can be sourced?How much current can be sourced?

• Is the voltage related to a fault, neutral Is the voltage related to a fault, neutral resistance, or other condition?resistance, or other condition?

• Is the voltage likely to change?Is the voltage likely to change?

1212

6.3.4.2.1 Measurement Circuit6.3.4.2.1 Measurement Circuit6.3.4.2.2 Voltage Measurements6.3.4.2.2 Voltage Measurements

• Open circuit voltage measurementsOpen circuit voltage measurements

• Reference must not be energizedReference must not be energized

~ AC Source

Rsource

Rshunt

Reference Ground

Voltmeter

1313

6.3.4.2.3 Current Measurements6.3.4.2.3 Current Measurements• Closed circuit (shunt voltage) measurementsClosed circuit (shunt voltage) measurements• Reference must not be energizedReference must not be energized• Reference and contact impedance must be lowReference and contact impedance must be low

AC Source

~ AC Source

Rsource

Rshunt

Reference Ground

Rground

Rcontact Rcontact

Voltmeter

1414

6.3.4.2.3 Current Measurements6.3.4.2.3 Current Measurements

• Use Pushbutton ShuntUse Pushbutton Shunt

• Compare open and closed circuit voltagesCompare open and closed circuit voltages

• Try alternate ground (earth) pointsTry alternate ground (earth) points

• Interpret results, know when to conclude measurementsInterpret results, know when to conclude measurements

~ AC Source

Rsource

Rshunt

Reference Ground

Rground

Rcontact Rcontact

Voltmeter

• Key ConceptsKey Concepts• Determine RDetermine Rsourcesource

• Minimize Minimize RRground ground RRcontactcontact

1515

Interpret ResultsInterpret Results

• Assume ground and contact resistances Assume ground and contact resistances lowlow

• High VHigh Vococ (50 Volts) Low V (50 Volts) Low Vcc cc (0.9 Volts)(0.9 Volts)

• Safe?Safe?

• Low VLow Vococ (3 Volts) Low V (3 Volts) Low Vcc cc (2 Volts) (2 Volts)

• Safe?Safe?

1616

Interpretation only possible when:Interpretation only possible when:

• Steps are taken to confirm low ground Steps are taken to confirm low ground and contact resistance and ground is not and contact resistance and ground is not energizedenergized

• VVococ Open Circuit Voltage measured Open Circuit Voltage measured

• VVcc cc Closed Circuit Voltage measuredClosed Circuit Voltage measured

1717

Shunts & GroundsShunts & Grounds

• Shunt should eliminate phantom voltageShunt should eliminate phantom voltage

• 500 ohms – low impedance500 ohms – low impedance

• Important to find low impedance groundImportant to find low impedance ground

• 3000 ohms – eliminates phantom voltage3000 ohms – eliminates phantom voltage

• If: Ground impedance = 50 ohmsIf: Ground impedance = 50 ohms

• Then: Measurement error –Then: Measurement error –• 10 % with 500 ohm shunt10 % with 500 ohm shunt

• 1.6% with 3000 ohm shunt1.6% with 3000 ohm shunt

• Understand importance of ground impedanceUnderstand importance of ground impedance

1818

Next Steps (for this section)Next Steps (for this section)

• Additional measurement scenariosAdditional measurement scenarios

• Analysis of dataAnalysis of data

• Specific examplesSpecific examples

• Additional measurements and their utilityAdditional measurements and their utility

• NEV treatmentNEV treatment

• Structure specific informationStructure specific information

• INPUT WELCOMEINPUT WELCOME

1919

6.3.4.2 Safety Standards6.3.4.2 Safety Standards

The New York State Electric Safety Standards currently state the following:Structures with voltage that measures 1 volt or greater with a 500 ohm shunt should be barricaded and guarded until properly mitigated. Any temporary repair should be periodically monitored until permanent repair is made.

2020

6.4 Mitigation6.4 Mitigation

• Typical repairs by structure typeTypical repairs by structure type

• Unusual findingsUnusual findings

• TrendsTrends


6.5 Case Studies6.5 Case Studies


Trial Use Guide For Assessing Voltages At Publicly and Privately Accessible Locations (P1695) Section 6 Contact Voltage Scott Kruse Power Survey Company.

Documents