NEC Equipment Ground Fault Settings - 30-100 mA vs 1200A

[lm227]

Can someone explain why there is such a big swing in the NEC in terms of ground fault allowed for equipment protection?

230.95 allows setting ground fault protection of equipment to pickup at 1200A

Whereas sections like 555.35 call for ground fault protection of equipment to pickup at 100mA

Why such a large ground fault setting swing between these different code sections?
Why are higher ground faults exponentially more "tolerable" at a 3000A 480V breaker vs a dock feeder or heat trace feeder?

 

[jim dungar]

Why such a large ground fault setting swing between these different code sections?
Why are higher ground faults exponentially more "tolerable" at a 3000A 480V breaker vs a dock feeder or heat trace feeder?

Selective coordination.

It is usually more preferable to limit an outage to a branch circuit or feeder versus having the main for the building open.
40 years ago coordination was difficult, now it is so relatively easy to do, I don't know why people try to design GF protection out.

 

[hillbilly1]

Leakage adds up quicker with multiple equipment. Parking lot feeds have notoriously high leakage due to water intrusion in conduits and boxes. I saw one Best Buy store in Minnesota, where they had so much leakage in the parking lot, they installed a separate non-ground fault service just for the parking lot, instead of fixing the problem. A normal 480 volt parking lot can have several amps of leakage, and still function. Add a few dozen a/c compressors that leak current, and it adds up. I have seen as much as 100 total amps of leakage on a large service.

 

[don_resqcapt19]

Can someone explain why there is such a big swing in the NEC in terms of ground fault allowed for equipment protection?

230.95 allows setting ground fault protection of equipment to pickup at 1200A

Whereas sections like 555.35 call for ground fault protection of equipment to pickup at 100mA

Why such a large ground fault setting swing between these different code sections?
Why are higher ground faults exponentially more "tolerable" at a 3000A 480V breaker vs a dock feeder or heat trace feeder?

Because the requirements are for totally different reasons. The one in 230.95 is an attempt to prevent arcing ground faults from "burning down" equipment fed from a 480Y/277 volt system, and the one in 555.35 is an attempt to limit the leakage current in the water for the safety of people.