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#173981 - 01/24/08 05:03 PM EC&M: 4,160 Volt Arc Blast  
BigJohn  Offline
Member
Joined: Mar 2004
Posts: 391
Boston, MA
I reading this months EC&M magazine and was struck by this story. It tells of an electrician who died from the effects of an arc-blast caused while attempting to lock-out a piece of 4,160 volt switchgear.

Apparently the electrician was using a meter that failed to clearly specify that the dislay was showing "kilovolts" instead of "volts." The electrician read a phase-to-ground measurement of "2.4" and assumed volts. He then attempted to make a hard ground to the energized point and caused an arc-flash.

Consider:
  • The victims first two attempts to test for voltage failed.
  • He then chose to employ a meter which he was apparently unfamiliar with (he did not understand what the display was reading).
  • After getting different readings at different points, he didn't attempt to resolve that discrepancy or test the meter on a known energized terminal.
  • The electrician failed to recognise that 2.4 would be the correct phase-to-ground reading in kilovolts for that system.
  • After only a single effective test with a single, unfamiliar meter, he assumed the gear was de-energized.
  • The electrician was not wearing any sort of arc flash protection.
  • He apparently did not understand the layout of that piece of switchgear and couldn't tell what terminals may be energized or why.
While everybody is fallable and everybody makes mistakes, given all the above, it seems to me that the failure of the meter to display "kilovolts" is overshadowed by what seems like an extremely cavalier attitude by somebody who was prepairing to intentionally ground a conductor that could be energized at four-thousand volts.
I'd be interested to hear some more experienced opinions weigh in on this.

-John


Arc Flash PPE Clothing, LOTO & Insulated Tools

#174033 - 01/25/08 02:19 PM Re: EC&M: 4,160 Volt Arc Blast [Re: BigJohn]  
richxtlc  Offline
Member
Joined: Sep 2007
Posts: 10
Tampa, FL
I just read the article that you referred to. The electrician made several mistakes, one which the investigator missed, that is, a circuit is considered energized until after it has been grounded, not just after it has been checked for absence of potential. Only those circuits that do not require grounding, eg, no danger of backfeed, no inductive coupling, etc., are considered in an electrically safe work condition after checking for absence of potential.

The fact that he was unfamiliar with the instruments he used to test the circuit violated OSHA requirements to be familiar with the proper testing procedures. Yes, he was trained, did follow protocol, wore most of the PPE required for work on de-energized equipment, but he was lacking in the required arc flash protection, probably HRC 4 for working in the switchgear, but the circuit was still considered alive for both NFPA-70E and OSHA.

Also, in work of the magnitude a safety meeting with all those involved, especially given the lack of experience of the other members of the team, should have been held to discuss how the work was going to evolve, including all PPE, testing requirement, grounding practices, LOTO clearances, etc., which obviously was not done. If so, this might have been avoided.



#174045 - 01/25/08 05:02 PM Re: EC&M: 4,160 Volt Arc Blast [Re: BigJohn]  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Well then,
Please bear in mind that most of the test gear I've ever used on HV equipment has always been of the Non-Contact type.

I'm not sure what sort of a meter the guy was using, but if it will carry that sort of voltage on contact, it must be pretty robust.

People that aren't experienced in HV work, should at the very least be under the supervision of someone that is.



#174095 - 01/26/08 01:10 PM Re: EC&M: 4,160 Volt Arc Blast [Re: richxtlc]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Originally Posted by richxtlc
I just read the article that you referred to. The electrician made several mistakes, one which the investigator missed, that is, a circuit is considered energized until after it has been grounded, not just after it has been checked for absence of potential.


Could you point out the OSHA standard for that?

That is not the case under 600 volts, is that for systems above 600 volts?

By the way, welcome to the forum. smile


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#174101 - 01/26/08 05:52 PM Re: EC&M: 4,160 Volt Arc Blast [Re: iwire]  
Zog  Offline
Member
Joined: Sep 2005
Posts: 120
Charlotte, NC
1920.269


MV/HV Testing Specialist, "BKRMAN"

#174104 - 01/26/08 07:05 PM Re: EC&M: 4,160 Volt Arc Blast [Re: Zog]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Originally Posted by Zog
1920.269


I assume that was 1910.269?

That section applies to Electric Power Generation, Transmission, and Distribution. I take that to mean utility workers.

The story in this thread starts with..

Quote
When an experienced electrician began working on the switchgear of a medical facility's main control room,


IMHO 1910.269 does not apply to this worker.



Last edited by iwire; 01/26/08 07:09 PM.

Bob Badger
Construction & Maintenance Electrician
Massachusetts

#174107 - 01/26/08 08:18 PM Re: EC&M: 4,160 Volt Arc Blast [Re: iwire]  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
I am NOT trained for working on 'high voltage' wiring, so my understanding of such matters may be wrong.

From all I've heard, grounding conductors is a basic precaution in working on power distribution systems. 4000 Volts seems to put this gear squarely in the 'distribution' category, whether utility owned, or not.

I would, in that case, want to be very familiar with NESC requirements. This gear seems a bit beyond NEC and UL expertise.

This, then, brings up the matter of qualifications. I can't see where your 'typical' electrician, or engineer, has any expertise on these matters. The article was woefully silent in regards to any special qualifications that may have been had by any of the parties involved.

This is not to 'flame' the article; I, for one, would love to know where to get such expertise .... BEFORE I need it.

The "Forensic Casebook" articles, unfortunately, seem to have more sizzle than steak. Far too often, important details are omitted, and the story ends with "we had a favorable, if confidential, settlement."

Can there be an overlap between differing parts of the trade? Absolutely - it happens all the time. Unfortunately, far too often training in these areas is far too often employer or manufacturer dependent. This accident may have been the natural conclusion to such circumstances.


#174112 - 01/26/08 10:07 PM Re: EC&M: 4,160 Volt Arc Blast [Re: renosteinke]  
frenchelectrican  Offline
Member
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
My SOP for the MV system is proper protection and use the hotstick and test and i mean test the voltmeter to make sure you know it will work properly before you get on the MV/HV system.

each test equmient have sligtly diffrent way to read the info on it and have to get famuiair with before you use it and know what is the limit what it can use on partaicar system.

but to work on MV/HV need a specal training to be well aware with arc flash and poitontal flashover and exsting sistuation as well.
unforetally some of the training can crossover between the two diffrent type of system and need a proper prodcures to work around engerized equiment there.

Merci, Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


#174144 - 01/27/08 03:08 PM Re: EC&M: 4,160 Volt Arc Blast [Re: frenchelectrican]  
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Mike, we do use contact phasing and test sticks on 11 kV Hazelmeijer switchgear.

Also we have contact phasing sticks up to 33 kV for G&B work.

Last edited by RODALCO; 01/27/08 03:08 PM.

The product of rotation, excitation and flux produces electricty.

#174252 - 01/30/08 07:58 AM Re: EC&M: 4,160 Volt Arc Blast [Re: BigJohn]  
richxtlc  Offline
Member
Joined: Sep 2007
Posts: 10
Tampa, FL
I have worked with medium/high voltage for more than 30 years in the utility industry and for the past few years in the commercial sector. As stated by several people, work at this voltage level requires special training and procedures, including specialized test equipment. OSHA 1910.333(b)(2)(ii)(C)and .333 (b)(2)(iv)[A]and [B} both determine how high energy circuits should be handled. It states handling of capacitors or other high capacitive elements, but if you have ever worked with medium voltage before then you know that the meter sometimes bounces when contact is made indicating a stored charge on the bus.
In addition to the OSHA reference, NFPA-70E 120.1 also refers to grounding when the possibility of induced or stored energy exists.
Although NFPA-70E was not included in this years OSHA update, it can still be used under the General Duty clause of OSHA in a legal case., The record of success when interperting the General Duty clause when failure to apply the provisions of 70E to a given situation is referenced is close to 100%.



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