15kv Cable

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newt

Senior Member
Can you use a tape shielded cable (shield sized for fault current not neutral current)on a primary 12kv underground system were there is aneutral conductor run withe the 3 phase conductors?The problem I see is they bond this neutral cond. with tape shield in manholes creating parralell path for return current on the tape shield.Doesnt that stress the termination that was not meant to carry current?
 

jtester

Senior Member
Location
Las Cruces N.M.
Re: 15kv Cable

In my experience, if you use a shielded conductor, you must install a neutral/ground along with it in a grounded wye system. If you don't you will force the tape to carry a larger amount of current than designed for, either under steady state or fault conditions.

I don't believe that tape shields are designed for fault carrying capabilities, only for shielding.

Jim T
 

newt

Senior Member
Re: 15kv Cable

If the shield and neutral are tied together at terminations then you would have return current on tape shield?Should this cable be wire shield (capable of carrying neutral current)should the bonding be different to keep them isolated?
 

jtester

Senior Member
Location
Las Cruces N.M.
Re: 15kv Cable

If your cable is truly shielded with either wire or tape, and not concentric neutral, it won't carry significant fault currents, you need a separate neutral/ground in a grounded wye system. The shield must be bonded at every termination to avoid an energized shield and the danger of a shock. It shouldn't cause problems.

Jim T
 
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