The solution of associating which motor starts with the
ground fault light is good. One solution I used in a paper
mill was to use a ground tracer, which put a buzz tone on the
particular PDC, with the ground fault. Using the earphones
and the probe coil, you could hear which drive might have
a bad motor or feeder, if you opened the starter doors,
and got the probe coil close to the load side terminals.
This ground tester had 3 lamps, as ground detectors,
and the buzz could be switched to any phase. The tester's
ground wire had to be placed carefully.
Grounds were not too high a priority in an operating
plant, and done on the fly. Of course if a second ground
happened on another phase, something would blow, perhaps
clear the first ground, or shut down a motor with blown
fuses.
The part of the plant with the worst grounds was the
wood mill division, with timber up out of the saltchuck.
Water and vibration was everywhere.
The biggest motor on the 575 volt side
was 250 HP, everything bigger was 2300 Volt.
Steam rams were used to flip logs and there always
was sawdust burning around the cylinders in the basement
and on the cable trays, so sometimes it was a cable fault.
One caveat here, I worked in pulp and paper, and what
we did may not be safe or customary in mining.
