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Thread: Using MV Cable Shield for Equipment Ground Conductor

  1. #1
    Join Date
    Oct 2008

    Using MV Cable Shield for Equipment Ground Conductor

    Is there anywhere in the NEC or elsewhere that permits the use of the internal cable shield on an MV cable to be used as an equipment ground conductor and satisfy the requirements of 250.122?

    A project I am involved with has an MV feeder (4 sets of 750 MCM) between an feeder breaker and the downstream equipment with no separate EGC's run with the feeders. It appears that they are using the internal cable shield for any grounding or ECG requirements.

    This is a 4.16kV LRG system (400A) so perhaps this is permissible on an LRG system with reduced fault current as opposed to a solidly grounded system?

  2. #2
    Join Date
    Feb 2003
    Read 250.190(C)


  3. #3
    Join Date
    Jan 2016
    do you have single individually shielded conductors or a cable assembly?

    you a 3 ph mv cable without a ground? (other than the shields)
    don't think I've ever seen one
    do you have a mfg/pn?

    looks acceptable if the lrg limited current can be carried without damage for the requied trip time

    what is your ngr ohmic value?
    whatgf trip value? any time delay?

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