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138 Kv clearence #58539 11/12/05 02:36 PM
Joined: Mar 2005
Posts: 399
A
Alan Nadon Offline OP
Member
I need some help from line men or eng. familiar with high voltage on this question.

An installation is going in that has 138 Kv primary service. There are uninsulated bus tubes (bars) from the disconnect switch arms to the top of the distribution panel. The bus tubes are four feet apart until the get to the top of the equipment and then they are reduced to being only 8 inches apart where they enter.
The bus bars inside the equipment is insulated, the ones coming in are bare.
Outside they are exposed to the elements, i. e. snow, rain, etc.

Is 8 inches of clearence enough at 138 Kv. ??

This is a customer owned installation and I can't find this in the NEC. Would the Life Safety Code have it ?
Any good formulas on clearence or sites would be appreciated.
Thanks.
Alan--Inspector


Alan--
If it was easy, anyone could do it.
Work Gear for Electricians and the Trades
Re: 138 Kv clearence #58540 11/12/05 02:48 PM
Joined: Mar 2001
Posts: 2,056
R
Redsy Offline
Member
How about the NESC?
National Electrical Safety Code.

Re: 138 Kv clearence #58541 11/12/05 05:52 PM
Joined: Oct 2005
Posts: 20
R
royal12136 Offline
Member
Hi Alan,
So far all I can find is this: http://www.pjm.com/planning/to-standards/downloads/20020520-va-general-criteria.pdf
On page 11, Table 1 under spacers, it say's 18" spacing, no preformed wire spacers allowed. This is for on the poles, but it should be the same for your situation.
Hope this helps,
Tim

Re: 138 Kv clearence #58542 11/12/05 10:53 PM
Joined: Sep 2005
Posts: 202
W
WFO Offline
Member
Are you saying 138 KV or 13.8 Kv?

8 inches isn't nearly enough at 138 KV.

Re: 138 Kv clearence #58543 11/13/05 11:56 AM
Joined: Mar 2005
Posts: 399
A
Alan Nadon Offline OP
Member
WFO
It is 138 Kv that is 138,000 Volts !

That is what has me asking. I don't think an eight inch clearence is enough. But, I don't know how much it should be, especially the clearence between bare conductors exposed to the elements.
This stuff is on the border between electricity and lightning.
If I'm going to challenge the spacing I need a reference. I'll check out Royal's reference it is a start.
Alan--


Alan--
If it was easy, anyone could do it.
Re: 138 Kv clearence #58544 11/14/05 08:06 PM
Joined: Jan 2005
Posts: 14
Z
zorinlynx Offline
Member
Curiosity killed the cat, but...

What sort of facility uses so much power that 138kV is required to feed it? I mean, we're talking *transmission* level voltage here! Scary stuff.

-Z

Re: 138 Kv clearence #58545 11/19/05 06:10 PM
Joined: Oct 2005
Posts: 20
R
royal12136 Offline
Member
Alan,
What have you found out so far?
From a post from resqcapt19 on another topic we get this information: http://www.highvoltageconnection.com/articles/highvoltagespacing.pdf
And form what it looks like it is saying to me is [Linked Image]138 kv*3)/10000= 41.4 inches minimum spacing for bare conductors.
I hope that this helps and that I understand this properly.
Tim

Re: 138 Kv clearence #58546 11/19/05 08:58 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Alan are you sure about the voltage?

Is it possible someone wrote or said 138 KV when they really meant 13.8 KV?

In my area 13.8 is a very common voltage for neighborhood and industrial distribution.

I agree with the others that 138 KV would be unusual for all but a few installations.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Re: 138 Kv clearence #58547 11/19/05 09:26 PM
Joined: Jan 2003
Posts: 4,391
I
iwire Offline
Moderator
Alan I think if you look carefully at the link I will provide you will be able to find pdf files that have the info you need.

http://www.lni.wa.gov/wisha/rules/electricalworkers/45-3.htm


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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