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#41895 - 09/10/04 11:27 AM Repairing DC electrical service
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
We have a DC electrical service with, one bad leg. Looking to replace the conductors. My question is, as I have limited experiance with DC, what type of PPE would be required to cut, and reconnect this service live?

Or is that just a dumb question?
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Mark Heller
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#41896 - 09/10/04 11:37 AM Re: Repairing DC electrical service
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
I am sorry I can not answer your question surly someone here can, but I did want to say that it is not a dumb question.

Pat yourself on the back for asking questions about safety. I only had to deal with a DC service once and the unknown made me very nervous.

Bob
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Bob Badger
Construction & Maintenance Electrician
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#41897 - 09/10/04 02:12 PM Re: Repairing DC electrical service
dereckbc Offline
Member
Registered: 10/08/03
Posts: 156
Loc: Tulsa, OK
I design a lot of DC power plants. What voltage and power levels are you talking about?
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#41898 - 09/10/04 02:58 PM Re: Repairing DC electrical service
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
100A -150A 240VDC Thanks!!!
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Mark Heller
"Well - I oughta....." -Jackie Gleason
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#41899 - 09/10/04 09:32 PM Re: Repairing DC electrical service
Peter Offline
Member
Registered: 06/08/04
Posts: 92
Loc: San Diego
Why do you have to do this live? Is this so important an installation that you will risk getting blinded, burnt, killed?
One thing I know about DC is that it has no neutral point, so that means you would be cutting it at full amperage.
Would it be possible to attach a temporary bypass around the damaged section you wish to cut out?
~Peter
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#41900 - 09/10/04 10:21 PM Re: Repairing DC electrical service
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: West-Southern Inner-Northeast ...
Should not a lot different than an AC circuit of similar ratings.

Can you deenergize the source to work on it? Obviously, a DC voltmeter/indicator would be used to check for dead.
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#41901 - 09/10/04 11:34 PM Re: Repairing DC electrical service
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
It's a customer owned U/G service lateral prior to the disco, the utility won't drop the area, of course, or re-pull it. We are trying to get them to cut, and re-connect. But, "P" stands for premidona, in PG&E, (Our POCO, actually SF County Hetch Hechy, but they maintain it.)so they may cut, and not re-connect. (Or vise versa.)Leaving our customer without an elevator.
----------------------------------
I can kill it at Zero Amps, by killing the disco, as it already is, but the voltage in a Christy box, leaning in a hole is what I worry about. Reaching in an live 240/480VAC street box, doesn't bother me. I know the risk, and the protection level for it. With DC, I have always worked dead, and locked out.

[This message has been edited by e57 (edited 09-11-2004).]
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Mark Heller
"Well - I oughta....." -Jackie Gleason
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#41902 - 09/11/04 05:13 AM Re: Repairing DC electrical service
Roger Offline
Member
Registered: 05/18/02
Posts: 1716
Loc: N.C.
I agree, this is not a dumb question.

If the situation can not be made safe then it may be a job you don't want.

I know that is easier to say than do.

From someone who was burnt in an arc blast, I will say, living without scars and going home healthy is whats important.

We work a lot of hot situations in hospitals, but if the situation is to precarious, a "SHUTDOWN" will be scheduled for late night, early morning, holiday, etc... regardless of inconvenience or expense.

I'm sorry I don't have any real info on your original question.

Roger
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#41903 - 09/12/04 05:44 PM Re: Repairing DC electrical service
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
Hey Bjarney, Thanks!

00 gloves are rated for 500VAC/750VDC
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Mark Heller
"Well - I oughta....." -Jackie Gleason
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#41904 - 09/12/04 05:53 PM Re: Repairing DC electrical service
CTwireman Offline
Member
Registered: 02/07/02
Posts: 840
Loc: Connecticut, USA
OK, I have to ask. What is the application for this DC service? And DC services in general.

Peter
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