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tmc7
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Post subject: Verifying "Dangerous" Category is Deenergized Posted: Thu Feb 25, 2010 1:44 pm |
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Joined: Thu Feb 25, 2010 1:24 pm Posts: 1
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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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Zog
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Post subject: Posted: Thu Feb 25, 2010 5:44 pm |
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Joined: Mon Jun 02, 2008 11:58 am Posts: 1103 Location: Charlotte, NC
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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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Canuck01
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Post subject: Posted: Thu Feb 25, 2010 7:36 pm |
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Joined: Wed Sep 23, 2009 9:29 pm Posts: 83 Location: Western Canada
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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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wbd
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Post subject: Posted: Fri Feb 26, 2010 6:10 am |
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Plasma Level |
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Joined: Wed May 07, 2008 5:00 pm Posts: 879 Location: Rutland, VT
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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)?
_________________ Barry Donovan, P.E. www.workplacesafetysolutions.com
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Vincent B.
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Post subject: Posted: Fri Feb 26, 2010 6:45 am |
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Joined: Tue Feb 24, 2009 7:05 am Posts: 252
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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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Zog
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Post subject: Posted: Fri Feb 26, 2010 7:45 am |
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Joined: Mon Jun 02, 2008 11:58 am Posts: 1103 Location: Charlotte, NC
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A panel mounted meter does not meet the requirements of 120.1(5) of the 70E.
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Canuck01
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Post subject: Posted: Fri Feb 26, 2010 12:38 pm |
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Joined: Wed Sep 23, 2009 9:29 pm Posts: 83 Location: Western Canada
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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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jghrist
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Post subject: Posted: Mon Mar 01, 2010 7:48 am |
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Joined: Wed Jun 04, 2008 9:17 am Posts: 428 Location: Spartanburg, South Carolina
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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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Canuck01
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Post subject: Posted: Mon Mar 01, 2010 6:05 pm |
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Joined: Wed Sep 23, 2009 9:29 pm Posts: 83 Location: Western Canada
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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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Canuck01
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Post subject: Posted: Tue Mar 09, 2010 10:33 am |
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Joined: Wed Sep 23, 2009 9:29 pm Posts: 83 Location: Western Canada
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minni-mo
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Post subject: Posted: Wed May 19, 2010 7:48 am |
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Joined: Mon May 17, 2010 11:29 am Posts: 3 Location: K.C. MO.
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check two items feed down stream with lower hrc frist then verify the the dangerous
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jghrist
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Post subject: Posted: Thu May 20, 2010 11:07 am |
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Joined: Wed Jun 04, 2008 9:17 am Posts: 428 Location: Spartanburg, South Carolina
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Canuck01 wrote: https://event.on24.com/eventRegistration/EventLobbyServlet?target=registration.jsp&eventid=197971&sessionid=1&key=CFEF79712F935A639C8FE0BD379D4E3B&sourcepage=register[/URL]
A free webcast from Fluke for those who are interested... I get the message Quote: The session you have requested could not be found in our database. Please check the URL and try again.
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