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Topic Title: Sub-main cut - Cables being joined using an Isolator
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Created On: 16 May 2013 12:29 PM
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 16 May 2013 12:29 PM
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calumbtw

Posts: 18
Joined: 22 October 2012

Hi,

Part of a lv sub-main cable was cut & stolen. We have decided to install an isolator between the new cable supplied from the switchgear, and the rest of the existing cable that feeds the DB.

Never come across this..how do I calculate the volt drop? Should they be two separate cables or calculated as one? Should they be the same size etc? Any regulations reg. this?

Sorry if I haven't made it clear...any help would be appreciated. Thanks.
 16 May 2013 12:49 PM
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AJJewsbury

Posts: 10964
Joined: 13 August 2003

how do I calculate the volt drop? Should they be two separate cables or calculated as one?

Assuming that the new cable is the same c.s.a. etc as the old one, it doesn't matter - you can calculate it either way and the answers should add up the same. If the new cable is different from the original, you'd have a different mV/A/m figure to work with, so you'd have to do it as two different sections and add the results together.
- Andy.
 16 May 2013 12:52 PM
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perspicacious

Posts: 7032
Joined: 18 April 2006

Did the last PIR or EICR carried out on this cable before it was stolen raise any concerns about it being the incorrect size?

Regards

BOD
 16 May 2013 01:12 PM
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calumbtw

Posts: 18
Joined: 22 October 2012

Originally posted by: AJJewsbury

how do I calculate the volt drop? Should they be two separate cables or calculated as one?


Assuming that the new cable is the same c.s.a. etc as the old one, it doesn't matter - you can calculate it either way and the answers should add up the same. If the new cable is different from the original, you'd have a different mV/A/m figure to work with, so you'd have to do it as two different sections and add the results together.

- Andy.


Ok, thanks for that Andy

Originally posted by: perspicacious

Did the last PIR or EICR carried out on this cable before it was stolen raise any concerns about it being the incorrect size?



Regards



BOD


Nope not that I am aware of.

Thanks for the help!
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