2400V Ungrounded Delta service - Ground Detector required?

[JDBrown]

A fellow Engineer stumped me with a Code question today (I'm sure that never happens to you guys). He's got a customer with a 2400V ungrounded delta service, and is trying to find what (if any) requirements there are for ground detection. To me it seems that installing a ground detector would be a good idea, regardless of whether it's required or not, but it sounds like the Customer is reluctant.

So... is a ground detector required in this scenario?

I'm in California, so I'm using NEC 2014 / CEC 2016. So far, I've found a few sections like 250.20(C) that require or permit certain systems over 1000V to be grounded, which implies that other systems could be left ungrounded. I also see requirements for Impedance Grounded Neutral Systems over 1000V in 250.187. For systems below 1000V, circuits that don't have to be grounded are addressed by 250.21 (including requirements for ground detectors), but I haven't been able to find an equivalent section for over 1000V.

So, it looks like we have the following:

• solidly grounded systems below 1000V - lots of Code requirements
• solidly grounded systems over 1000V - lots of Code requirements
• impedance grounded systems below 1000V - lots of Code requirements
• impedance grounded systems over 1000V - lots of Code requirements
• ungrounded systems below 1000V - lots of Code requirements
• ungrounded systems over 1000V - NO CODE REQUIREMENTS AT ALL???

Is this right? Please tell me I've missed an Article somewhere.