Grounding of Systems over 1 KV

I've done it that way. Derive the ground from the secondary side of the transformer. The utility acts as it's own inspector, do what they tell you. When you say shielded cable I think you really mean amoured cable from the pole to the switch.

Actually, it is a shielded cable (3) installed inside of 4 inch PVC conduit. The customer owns the primary from the load side of the cut outs on the pole. I am not the contractor; I am the inspection authority. One of my inspectors have already approved the installation and the utility company subsequently energized the service.

The question was brought to my attention after the fact by an interested party and I'm trying to sort through it and make sure it meets the NEC. I can not find any requirement in Article 250 that requires, for systems operating at over 1kv, to be grounded where supplied by a utility system that is grounded. Article 250.20 & 250.24 are very clear that it is required for systems operating at 50 to 1000 volts, but grounding is only an option, for over 1kv.

Thanks,

Tim

Like I said, the Utility is generally it's own inpector. They deal with that level of power everyday and have worked out procedures and policies that insure safe operation of a power distribution system. Most Inspectors are not well versed in the power distribution side of things. They don't see it or work with it often enough. NEC trusts the Utility to make the correct connection decisions (without an outside inspector) for over 1KV applications. Most 13,800V lines in this area are not grounded, (other than static lines) so your statment of article 250 "systems operating at over 1kv, to be grounded where supplied by a utility system that is grounded" is quite correct and you should do as the Utility recommends. The Utility would not have energized the equipment if the thought it might cause an outage of the system.