Ground fault indicator gets bright during fault
Ground fault indicator gets bright during fault
(OP)
Hello, first post. Long story short, ground fault lights are referenced to ground and normally go dim or go dark if ground fault occurs. I have one now that gets brighter when 20 horse cooling tower motor is turned on. Phase to phase arcing within the motor?
3 phase ungrounded Y
Thanks,
Don S.
3 phase ungrounded Y
Thanks,
Don S.






RE: Ground fault indicator gets bright during fault
RE: Ground fault indicator gets bright during fault
RE: Ground fault indicator gets bright during fault
With an ungrounded system you typically see phase to neutral voltage between each phase and ground. but. If one phase is grounded then you get phase-phase voltage when measuring between the other two phases and ground (ground is now the same as one of the phases).
RE: Ground fault indicator gets bright during fault
RE: Ground fault indicator gets bright during fault
Consider the normal current through the lamps and the capacitive charging current of your system. Now consider how much this current must change to cause the lamps to brighten or dim noticably. This change in current is about the level of your leakage current. eg; Very low.
With one lamp going bright, the problem is on the other two phases. Look for single phase loads such as control transformers with damp windings, or one damp winding in a motor with delta connected windings. To megger you may have to disconnect the motor leads and check each winding individually.
yours.
RE: Ground fault indicator gets bright during fault
I haven't checked in to it yet since I am working a week of midnight's this week. When I do dive in I'll remove the motor from the circuit and Megger both ways.
Thanks all for the fuel for thought.
Regards, Don