GFI Breakers

[TConnolly]

I've used ground fault detection on switchgear, which usually results in a 'needle in a haystack' search for a bad motor. Is there a better way to narrow down where the fault is?

For motors use an Earth Leakage Relay. This is different from a GFI.

http://library.abb.com/GLOBAL/SCOT/scot260.nsf/VerityDisplay/D8A3B255544D297985257099004A46E4/$File/CM-IWN-AC.pdf

You wire the relay into your starter control cicruit or into a shunt trip breaker. They have an adjustable trip point from 1K to 110K ohms.

 

[Jim Dungar]

Do they make 480VAC GFCI breakers? If they do, how high of Amperage do they go?

We have issues in this plant where a ground faulted motor will take out the whole switchgear, thus causing a complete plant outage. Sometimes the fault is on an office air conditioner and the entire plant will suffer 6 hrs downtime to recover.

I've used ground fault detection on switchgear, which usually results in a 'needle in a haystack' search for a bad motor. Is there a better way to narrow down where the fault is?

Yes they make 480V breakers with Ground Fault Protection. Just do not confuse GF protection which is measured in amps with that of GFCI (sometimes incorrectly called GFI) people protection which is 5mA or GFPE (used on heater circuits) equipment protection which is in 30mA. Note: there are other terms and trip levels across the pond.

If you have a branch circuit take out your main breake it is because nobody paid for an engineering study which would have told you which settings (or additional eqipment) are required for proper coordination.

The methods for chasing down faults depends depends on if your system is solidly grounded (the most common), ungrounded (not common), or resistance grounded (becoming less rare).

 

[TimWilborne]

Here are some other names for the GFCI
http://forums.mrplc.com/index.php?showtopic=7119