High Resistance Grounding for voltage lower than 480 volts

[poweringtech]

If ungrounded system is applied to most voltages, How come there is a limit in the application of High Resistance Grounding to 480 volts and above only Article 250.36? Code should allow HRG to all voltage system lower than 1000 volts.

 

[George Stolz]

I think the biggest reason may be that the incident energy from lower voltage ground faults is as much as a fifth lower than a ground fault on a 480V system. If equipment is not likely to be as likely to be permanently damaged by a ground fault, there is less excuse to use the system.

Check out Mike Holt's recent newsletters on the topic for more information, I'm woefully underinformed as to the application of High Resistance Grounded systems.

http://www.mikeholt.com/newsletters.php?action=display&letterID=281

Edit to add: below is a link to the other thread in progress, about the same topic. Perhaps the discussion could continue over there?

http://www.mikeholt.com/code_forum/showthread.php?t=82235

 

[poweringtech]

"I think the biggest reason may be that the incident energy from lower voltage ground faults is as much as a fifth lower than a ground fault on a 480V system. If equipment is not likely to be as likely to be permanently damaged by a ground fault, there is less excuse to use the system."


If customer would want to have continuity of service and it is safe then why will NEC prevent the use of HRG for voltages lower than 480 volts? If NEC is minimum requirement for safety then it should allow HRG for voltages lower than 480 volts.