Ungrounded 12,470V System - Requirements

What does the code say? Local code, too.

What is the location?

Are you a licensed electrical contractor, licensed in the local in which you are now working????

Both of my codes says it is permitted to be grounded, but I could not locate anything that said it "HAD" to be grounded. I don't like that it is not grounded because of the transient overvoltages associated with it. I really want to ground it but with no code the client won't do it.

Then your next call should be to the local permitting/inspection agency to ask them.

Requirements vary from town to town, county to county and state to state.

Thanks - will do.

Authority Having Jurisdiction (AHJ).

Thanks.

If the 12,470V will be connected to the local utility's system, they may have something to say also. Check with their protection engineer.

I can't see why you have a problem with earthing the neutral point.

You don't say the size of this transformer or its intended use. A NER would be the usual option for MV but with no information it's just guess work.

This smacks of homework.

I can't earth the neutral point because the service is solidly grounded with induction disk relays (no directional ground fault detection) and the standby generators are grounded through a 200A impedance. The original design was to never island now they want to island.

"...The original design was to never island now they want to island...", all bets are now off. This is a radical departure from the original design and requires a new complete system study, including a review of the existing system and coordination with the local utility.

This is not a simple "handbook engineering" exercise; personnel and equipment safety are at issue, as well as code compliance and insurability. Hire a competent electrical power engineer who has done this type of thing before.

Tell them they can't do it! Then quit.

Try "ASK THE EXPERT" feature in www.igard.com"