primary distribution grounding

[farmer]

I have a 12470V primary with an underground switch. We needed to move the transformer to a new location making the wires too short. There is a ground wire circling the pit for the shield of the primary wires to drain to. The old run had a ground wire run with the primary wires to the transformer. The transformer has a ground rod inside of it and the secondary will terminate in a distribution panel which being the first disconnecting means will be grounded. Is the ground wire in the primary from the underground switch to the transformer necessary? The primary is 3 phase delta and the wire to the new transformer location is tape shield.

[ February 12, 2006, 06:07 PM: Message edited by: farmer ]

 

[Nick]

Re: primary distribution grounding

Yes. Shielding in MV cable is not intended to be nor does it qualify as an equipment grounding conductor. That is unless you have concentric neutral cable. In which case probably no. Then it depends on how your system is designed.

 

[Zifkwong]

Re: primary distribution grounding

I am having difficulty understanding exactly what you have or what you are doing but transformer case and the transformers primary ground switches must have an effective ground.

 

[Zifkwong]

Re: primary distribution grounding

Thanks for the PM farmer. It is still a little confusing as to how you are being fed from the utility. Do you have a feed that is above 12 kV or is this the main service?

If this is the main service then I would check with the utility to see what their requirements are. I would expect that they just want you to establish an effective ground system at your service location. If this is a feeder after your PCC then I would think that you need to connect the enclosure to the ground grid along with the equipment on both ends of the feeder. One method would be how you described, running a conductor within the same enclosure as the feeder.