Proximity Detector Question

Andrew B.

New Member
Dec 30, 2016
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#1
Can you shed any light on using proximity detectors to verify absences of voltage for LOTO below 60vac? I hear it both ways everywhere I turn.
 

Ken Sellars

Moderator
Staff member
Dec 30, 2016
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#2
Thank you for your question. I am assuming you meant 600V, not 60V, so I will answer based on that assumption.

The use of proximity detectors for verification purposes for lockout/tagout and/or creating an electrically safe work zone is not allowed in any circumstance. This is pointed out in NFPA 70E in Article 120.1(5), where it states, “Use an adequately rated test instrument to test each phase conductor or circuit part to verify it is de-energized. Test each phase conductor or circuit part both phase-to-phase and phase-to-ground. Before and after each test, determine that the test instrument is operating satisfactorily though verification on a known voltage source.” (from 2015 NFPA 70E). An informational note appears under that section directing the reader to ANSI/ISA 61010-1, which explains rating requirements for voltage measurement and test instruments for use on electrical systems 1000V and below.

The typical pocket-type proximity detector is not able to test circuits phase-to-phase or phase-to-ground. These detectors detect the presence of an electrical field, but do not in any way measure voltage. As anyone who has used these detectors in the past realize, they are not always reliable when other energized conductors are nearby, thus can yield false positives or negatives in varying circumstances. The 70E standard requires a meter that can actually test for the presence or absence of system voltage, measuring between phases and ground to ensure the lockout/tagout was sufficient.

The confusion comes in when we introduce the allowance of proximity detectors in circuits >600 volts. The OSHA 1910.269 standard requires detection of the removal of NOMINAL voltage, which is basically the expected system voltage, and then the application of grounds to ensure the system to be worked on is safe by grounding and creating an equi-potential zone for the HV worker(s). This is not the case in voltages 600V and below. In these cases, we need to verify the system is in fact de-energized because in most cases when working 600V and below, the worker(s) will not be installing personnel safety grounds.

Hope this explanation helps clear up the issue. If not, please let me know.
 

ezwages

New Member
Dec 17, 2018
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#3
on systems greater than 600V is it necessary to test P-P and P-G? There exist analog "contact" meters for use on HV systems that do not use a ground reference probe, but only consist of a single point of contact. Do you find these types of meters acceptable to prove the absence of nominal voltage?

example meter - Salisbury VDAH300
"VOLTAGE DETECTORS & VOLTMETERS consist of one high resistance unit connected in series with an ammeter calibrated to read approximate voltage. Voltage detectors create an incomplete electrical circuit because the single probe physically makes contact with one conductor potential while the live line tool attachment is floating at a variable potential."
 

Hugh Hoagland

Moderator
Staff member
Dec 30, 2016
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Louisville, KY
www.arcwear.com
#4