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 Post subject: Verifying "Dangerous" Category is Deenergized
PostPosted: Thu Feb 25, 2010 1:44 pm 

Joined: Thu Feb 25, 2010 1:24 pm
Posts: 1
When verifying that a conductor or circuit has been deenergized, the appropriate PPE must be worn to verify nominal voltage. How do others verify zero voltage on 40+cal panels when there is no PPE rated to protect the person?


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PostPosted: Thu Feb 25, 2010 5:44 pm 
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Location: Charlotte, NC
tmc7 wrote:
When verifying that a conductor or circuit has been deenergized, the appropriate PPE must be worn to verify nominal voltage. How do others verify zero voltage on 40+cal panels when there is no PPE rated to protect the person?


I have never seen a good answer for that one, every plant has the same question. Use distance as your friend by suiting up and using hot stick mounted meters or phasing sticks and shotguns for applying your grounds if required.

The best solution is mitigating the hazard level to <40cal/cm2.


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PostPosted: Thu Feb 25, 2010 7:36 pm 
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Location: Western Canada
Zog wrote:
I have never seen a good answer for that one, every plant has the same question. Use distance as your friend by suiting up and using hot stick mounted meters or phasing sticks and shotguns for applying your grounds if required.

The best solution is mitigating the hazard level to <40cal/cm2.

Zog, I agree 100%
Some of my questions are:
Does the test need to be "touch" or is an inductive tester sufficient?
Should an Arc Flash label contain more than 1 working distance (like a testing distance) since there are places where the +40 cal IE might even extend beyond the reasonable access distance for the equipment.


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PostPosted: Fri Feb 26, 2010 6:10 am 
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Location: Rutland, VT
I guess there are several items to check:
1. In the AFH study, was a 2 sec cutoff used if you able to taking into account physical configuration?
2. Is it possible to lower the AFH by lowering the Inst setting on a feeder breaker if there is one?
3. Is this HRC of 4, for a working distance of 18"? What happens if the working distance is greater?
4. If contact testing is required, can long leads from a meter be attached to appropriate length hotsticks?
5. If proximity probe is acceptable, can that be attached to an appropriate hotstick?
6. Is it possible to use voltage meter installed on bus (if there is one)?

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www.workplacesafetysolutions.com


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PostPosted: Fri Feb 26, 2010 6:45 am 
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wbd wrote:
6. Is it possible to use voltage meter installed on bus (if there is one)?


If you see it at 0 V, does it indicate that there's no voltage on the bus or is it just malfunctioning or wrongly wired? Is voltage absent from all 3 phases (3x line-line and 3x line-ground) or is there a remaining live phase?

Permanently attached meters do have pitfalls.


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PostPosted: Fri Feb 26, 2010 7:45 am 
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A panel mounted meter does not meet the requirements of 120.1(5) of the 70E.


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PostPosted: Fri Feb 26, 2010 12:38 pm 
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Joined: Wed Sep 23, 2009 9:29 pm
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Location: Western Canada
Testing after de-energising

Is the test required to be contact or is a proximity test sufficient?

CSA Z462-098 Clause 4.2.1(e) or NFPA 70E 2004 120.1(5)
"Use an adequately rated voltage detector to test each phase conductor or circuit part to verify that
they are 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 voltage detector is operating
satisfactorily." Note: See CAN/CSA-C22.2 No. 61010-1 for rating and design requirements for voltage measurement and test
instruments intended for use on electrical systems operating at 1000 V and below.


I say contact testing under 1000 volts. Non-contact testing could be implied above the 1000 volt threshold.

Still, the question remains - how to verify absense of voltage when above 40 cal @ calculated working distance...
My thoughts:
Confirm the IE is accurate. Some studies are flawed (2 second rule, etc)
Run scenarios using different working distances. Find a distance with less than 40 cal. This still leaves the question of multiple labels on switchgear...


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PostPosted: Mon Mar 01, 2010 7:48 am 
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Location: Spartanburg, South Carolina
Could de-energizing (and verifying) upstream be acceptable if there is no other source of power and if the upstream location has a lower IE and can be de-energized? In particular, I'm thinking about the primary of a transformer where the high IE on the secondary is caused by slow primary overcurrent protection.


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PostPosted: Mon Mar 01, 2010 6:05 pm 
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jghrist wrote:
Could de-energizing (and verifying) upstream be acceptable if there is no other source of power and if the upstream location has a lower IE and can be de-energized? In particular, I'm thinking about the primary of a transformer where the high IE on the secondary is caused by slow primary overcurrent protection.

I like the idea of it, however upstream testing is really only good for an uncomplicated branch on the electrical system. Some installations (including mine) have multiple MCCs fed from the same transformer so it's not feasible to test upstream.


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PostPosted: Tue Mar 09, 2010 10:33 am 
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Webcast

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PostPosted: Wed May 19, 2010 7:48 am 

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Location: K.C. MO.
check two items feed down stream with lower hrc frist then verify the the dangerous


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PostPosted: Thu May 20, 2010 11:07 am 
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Canuck01 wrote:
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