# Lighting Control Panel Direct fault and or ground fault.



## HARRY304E (Sep 15, 2010)

Masio said:


> I have a scenario I would like your opinion on. Had a direct short to ground at a light pole in a parking lot. The fault current flowed all the way back blew the relay off the board and tripped the 400A main. this seems extreme. There was four 2 pole breakers tripped in the panel ( all four breakers were circuits on the same section of the control panel) the system is a 277/ 480 volt. all the lights are 480. I did some minor investigating work and found the 480 volt circuit that is the problem, but I was not the one who did the installation. Things I found. the lighting control panel was installed in pipe but no separate grounding equipment conductor was ran to the LC's equipment grounding bar(the installation goes through a gutter and then to the panel). The service is 400A feeding a 200A main breaker panel in witch they turned the 200A main disconnect into a disconnect for a separate 200A panel. So the panel witch once was a main breaker panel is now a main lug panel. This whole senerio seems odd. Keep in mind this is the outlet mall up in Tulip. Any ideas where I should start looking for troubleshooting? Is this a normal thing having a relay blown off the board when there is a fault? I would like to give these people some kind of answer on why this happened and know where to start to fix the problem. Hope I got this posted to the right area. Sorry new member.




No problem Welcome..:thumbup:

How did you make out?


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## Tom45acp (Sep 6, 2011)

I'll take a guess, I think that the fault current was greater than the rating of the lighting control panel. See if the panel is marked to indicate the maximum fault current that can be handled by the control panel. Your electrical system may exceed that value. I can't say what a typical lighting control can handle, but I've seen other types of control panels marked for a maximum available fault current of 5000 amps.


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## Spark Master (Jul 3, 2012)

The fault current was so high, it tripped the main. I have seen that on a phase to phase fault. Tripped a 20 amp, and a 100 amp sub main. The 800 amp for the building did not trip.

The fault current is in the 10's of thousands. Which is only limited by wire size.


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## brian john (Mar 11, 2007)

Which breaker trips is based on coordination and design based on the circuit breakers involved and it is not unusual for the problem you described to happen.

Two what they said about the relay.

Three find the fault repair and the issue you have with the CBs tripping is part of the design and little you can do about this now with out some major distribution changes.


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