Agreed. But that still means my install is not compliant.
I agree and a ground detector needs to be installed, I'm not sure when the ground detectors were first required but even my 1999 copy has it in 250-21(3)(d) but it was only for separately derived systems, so it might have been in the past that Ground detectors were not being used if the supply was an ungrounded system from the utility?
I know I would want them as I would want to know when a conductor went to ground because the next conductor that goes to ground will cause a fault and shut down the equipment which is why you want a ungrounded system in the first place.
I wouldn't care if they have done hundreds of installs with out Ground detectors, all that says is they have been doing it wrong for hundreds of times and that is bad.
Show them 250.21(B)
(B) Ground Detectors. Ground detectors shall be installed
in accordance with 250.21(B)(1) and (B)(2).
(1) Ungrounded alternating current systems as permitted in
250.21(A)(1) through (A)(4) operating at not less than
120 volts and not exceeding 1000 volts shall have
ground detectors installed on the system.
(2) The ground detection sensing equipment shall be connected
as close as practicable to where the system receives
its supply.
Ground detectors are used to provide a visual indication, an
audible signal, or both, to alert system operators and maintainers
of a ground-fault condition in the electrical system.
With notification of the ground-fault condition, rather than
automatic interruption of the circuit, the operators of the
process supplied by the ungrounded system can then take
the necessary steps to effect an orderly shutdown, determine
where the ground fault is located in the system, and can
safely perform the necessary repair
The above is from the 2011 with the commentary.
It has not changed much from the 2002 code cycle.
I agree that a crane is a good reason to have an ungrounded system but an ungrounded system without ground detectors totally defeats the reason for having an ungrounded system since you will not know when a phase went to ground until the second phase goes to ground then its to late.
Are you the inspector or is this work at a plant you work at? If the latter then I would show your boss (if it is appropriate) the above code and explain to him the reason I posted above.