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

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Presentation on theme: "Trial Use Guide For Assessing Voltages At Publicly and Privately Accessible Locations (P1695) Section 6 Contact Voltage Scott Kruse Power Survey Company."— Presentation transcript:

1 Trial Use Guide For Assessing Voltages At Publicly and Privately Accessible Locations (P1695) Section 6 Contact Voltage Scott Kruse Power Survey Company January 12, 2009 David Kalokitis Power Survey Company

2 2 Presentation Overview Objectives Objectives Time Frame Time Frame Description of effort to date Description of effort to date Outline of draft text Outline of draft text Feedback Feedback Discussion Discussion

3 3 Objectives Distribution of Section 6 Contact Voltage to all group members through . Distribution of Section 6 Contact Voltage to all group members through . Post on Working Group website Post on Working Group website All interested parties to read and provide feedback by sending word doc. with tracked changes and / or comments. All interested parties to read and provide feedback by sending word doc. with tracked changes and / or comments. Submit feedback to: Submit feedback to: Dave Kalokitis: Scott Kruse: Chuck DeNardo:

4 4 Time Frame Submit any edited text or comments by the end of April for inclusion into the next revision of the document. Submit any edited text or comments by the end of April for inclusion into the next revision of the document. Effort to date A small number of contributors have generated and mutually reviewed draft A small number of contributors have generated and mutually reviewed draft 22 pages 22 pages Many openings for needed contributions Many openings for needed contributions

5 5 6.1 Contact Voltage Definition Definition General Concerns General Concerns Shock Hazard Shock Hazard Shock Triangle Shock Triangle

6 Contact Voltage Discovery 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:

7 Contact Voltage Root Causes Insulation Degradation Insulation Degradation Failure of insulating materials Failure of insulating materials Neutral Corrosion / Burn Out Neutral Corrosion / Burn Out Current may return through ground Current may return through ground Neutral to earth voltage (NEV) due to resistance Neutral to earth voltage (NEV) due to resistance Workmanship Workmanship Reversed polarity Reversed polarity Improper insulation of connections Improper insulation of connections Construction Damage Construction Damage Excavation, Road work, Improper Repair of Damage Excavation, Road work, Improper Repair of Damage

8 Energized Structures Manhole Covers Manhole Covers Hand Hole Covers Hand Hole Covers Street Lights Street Lights Traffic Signals Traffic Signals Sidewalk / Roadways Sidewalk / Roadways Gates / Fences Gates / Fences

9 Test and Measurement Equipment Hand Held Detector Hand Held Detector Mobile E-field Detector Mobile E-field Detector Hand Held E-field Detector Hand Held E-field Detector Voltmeter Voltmeter Ground Lead Ground Lead Switchable Shunt Resistor Switchable Shunt Resistor Ground Rod Ground Rod Safety Equipment Safety Equipment

10 Locating, Measuring and Mitigating Contact Voltage Discovery Methods Discovery Methods Incident Incident Record Keeping, Communication Record Keeping, Communication Inspection Inspection Prescribed cyclic inspection of assets Prescribed cyclic inspection of assets Record Keeping Record Keeping Detection – Underground/Overhead Detection – Underground/Overhead Manual Survey Manual Survey Mobile Detection Mobile Detection

11 Measurements What is the voltage level on the energized surface? What is the voltage level on the energized surface? Is the voltage supplied through low or high impedance? Is the voltage supplied through low or high impedance? How much current can be sourced? How much current can be sourced? Is the voltage related to a fault, neutral resistance, or other condition? Is the voltage related to a fault, neutral resistance, or other condition? Is the voltage likely to change? Is the voltage likely to change?

12 Measurement Circuit Voltage Measurements Open circuit voltage measurements Open circuit voltage measurements Reference must not be energized Reference must not be energized ~ AC Source R source R shunt Reference Ground Voltmeter

13 Current Measurements Closed circuit (shunt voltage) measurements Closed circuit (shunt voltage) measurements Reference must not be energized Reference must not be energized Reference and contact impedance must be low Reference and contact impedance must be low AC Source ~ R source R shunt Reference Ground R ground R contact Voltmeter

14 Current Measurements Use Pushbutton Shunt Use Pushbutton Shunt Compare open and closed circuit voltages Compare open and closed circuit voltages Try alternate ground (earth) points Try alternate ground (earth) points Interpret results, know when to conclude measurements Interpret results, know when to conclude measurements ~ AC Source R source R shunt Reference Ground R ground R contact Voltmete r Key Concepts Key Concepts Determine R source Determine R source Minimize R ground R contact Minimize R ground R contact

15 15 Interpret Results Assume ground and contact resistances low Assume ground and contact resistances low High V oc (50 Volts) Low V cc (0.9 Volts) High V oc (50 Volts) Low V cc (0.9 Volts) Safe? Safe? Low V oc (3 Volts) Low V cc (2 Volts) Low V oc (3 Volts) Low V cc (2 Volts) Safe? Safe?

16 16 Interpretation only possible when: Steps are taken to confirm low ground and contact resistance and ground is not energized Steps are taken to confirm low ground and contact resistance and ground is not energized V oc Open Circuit Voltage measured V oc Open Circuit Voltage measured V cc Closed Circuit Voltage measured V cc Closed Circuit Voltage measured

17 17 Shunts & Grounds Shunt should eliminate phantom voltage Shunt should eliminate phantom voltage 500 ohms – low impedance 500 ohms – low impedance Important to find low impedance ground Important to find low impedance ground 3000 ohms – eliminates phantom voltage 3000 ohms – eliminates phantom voltage If: Ground impedance = 50 ohms If: Ground impedance = 50 ohms Then: Measurement error – Then: Measurement error – 10 % with 500 ohm shunt 10 % with 500 ohm shunt 1.6% with 3000 ohm shunt 1.6% with 3000 ohm shunt Understand importance of ground impedance Understand importance of ground impedance

18 18 Next Steps (for this section) Additional measurement scenarios Additional measurement scenarios Analysis of data Analysis of data Specific examples Specific examples Additional measurements and their utility Additional measurements and their utility NEV treatment NEV treatment Structure specific information Structure specific information INPUT WELCOME INPUT WELCOME

19 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.

20 Mitigation Typical repairs by structure type Typical repairs by structure type Unusual findings Unusual findings Trends Trends INPUT WELCOME INPUT WELCOME 6.5 Case Studies INPUT WELCOME INPUT WELCOME

21 21 Solicitation Need Text Need Diagrams Need Figures Need Case Studies Send word doc. with tracked changes and / or comments


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