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Topic Title: 3ph dead short & IT equipment
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Created On: 21 September 2009 06:01 PM
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 21 September 2009 06:01 PM
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Haggar

Posts: 21
Joined: 25 January 2008

I just found out that one of the guys working for me has had a dead short across 2 phases at the fuseboard, the circuits leading from this board have quite a bit of IT equipment on it, the dead phases wont be turned on until tomorrow but now there worried about the equipment and any possible damage? do we need to worry?
 21 September 2009 06:24 PM
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Haggar

Posts: 21
Joined: 25 January 2008

I should have mentioned that the equipment is 240v and not 400v
 21 September 2009 09:42 PM
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anastasis

Posts: 583
Joined: 01 September 2009

Can you clarify the question? Exactly what has happened?

But it's unlikely a phase-phase fault will cause an overvoltage so the downstream loads should be OK. Obviously computers prefer to be shut down properly, low.
 22 September 2009 01:46 PM
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AJJewsbury

Posts: 11364
Joined: 13 August 2003

Was it a simple L-L fault, or could N have been involved. I'm just thinking that N will go up to about half Uo (in phase with the faulty L) if there was a L-N fault, so single phase equipment connected to one of the other lines will see the L-N voltage increase somewhat for the duration of the fault.

Large fault currents might induce significant voltages in data cables too - all depending on where they're positioned in relation to the mains cables that carried the fault current.

- Andy.
 22 September 2009 01:52 PM
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anastasis

Posts: 583
Joined: 01 September 2009

Originally posted by: AJJewsburyall depending on where they're positioned in relation to the mains cables that carried the fault current.

But no-one would ever install data cables with less than the specified segregation distance from mains cables, would they?
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