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Topic Title: Fault Current Through Cable Armor
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Created On: 12 August 2010 09:03 AM
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 12 August 2010 09:03 AM
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Badshah

Posts: 38
Joined: 22 July 2009

Please clarify my doubts,

Does cable armor, acts as a return path during fault condition?
If in a distribution network, when there is absence of earth or ground due to theft in one substation. During fault, how the fault current returns to the source? If it is through the cable armor or sheath, whether it can withstand the full fault current?
If grounding is not available in the substation, does this have any impact on MV fuse operation?
Does the non-availability of grounding affects the power quality?
 12 August 2010 09:12 AM
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sfchew

Posts: 589
Joined: 10 December 2002

The cable armor can carry the fault current.

If earthing has been removed you have a non earthed system. There will be no return current if any phase is grounded. subsequent faults will bring about earth fault currents.

Un-earthed system can certainly affect the power quality and may cause severe damage on equipment.

Regards
Chris Chew
 22 August 2010 02:29 PM
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iqbalkhan

Posts: 43
Joined: 26 January 2009

Hi
Yes cable armor can carry the fault current but interestingly when the armor is not capable for that fault current then it is advisable to give another cable to carry the fault current .
ungrounded systems can rise high voltages
 22 January 2013 04:02 AM
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Badshah

Posts: 38
Joined: 22 July 2009

In most of the cases the copper cable connecting body equipotential earthing (not earth rod/plate) were missing in substation.
is it ok to provide a temporary grounding system (Underground MV system) connecting the LVDB, RMU & Transformer body to earth equipotential point. If yes, please advise when to provide the temporary grounding connection (before isolation or after isolation)

Thanks & Regards
Badshah
 22 January 2013 03:10 PM
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ade12306

Posts: 6
Joined: 24 April 2009

Under the regulations the armour is classed as a conductor, so if this fault path has been removed then you must replace it with a cable.

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Adrian Mitchell.
Group, Controls and Automation Engineer.
Shop Direct Group.
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