It is currently Tue Oct 03, 2023 4:37 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 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?


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Feb 25, 2010 5:44 pm 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
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.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu Feb 25, 2010 7:36 pm 
Sparks Level

Joined: Wed Sep 23, 2009 9:29 pm
Posts: 83
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.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Feb 26, 2010 6:10 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 879
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)?

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Feb 26, 2010 6:45 am 
Sparks Level

Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
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.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Feb 26, 2010 7:45 am 
Plasma Level

Joined: Mon Jun 02, 2008 11:58 am
Posts: 1103
Location: Charlotte, NC
A panel mounted meter does not meet the requirements of 120.1(5) of the 70E.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Fri Feb 26, 2010 12:38 pm 
Sparks Level

Joined: Wed Sep 23, 2009 9:29 pm
Posts: 83
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...


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Mar 01, 2010 7:48 am 
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
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.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Mon Mar 01, 2010 6:05 pm 
Sparks Level

Joined: Wed Sep 23, 2009 9:29 pm
Posts: 83
Location: Western Canada
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.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Tue Mar 09, 2010 10:33 am 
Sparks Level

Joined: Wed Sep 23, 2009 9:29 pm
Posts: 83
Location: Western Canada
Webcast

https://event.on24.com/eventRegistratio ... e=register[/URL]

A free webcast from Fluke for those who are interested...


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed May 19, 2010 7:48 am 

Joined: Mon May 17, 2010 11:29 am
Posts: 3
Location: K.C. MO.
check two items feed down stream with lower hrc frist then verify the the dangerous


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Thu May 20, 2010 11:07 am 
Arc Level

Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
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.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2022 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883