1000A Main Breaker Trip During a Storm

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ed downey

ed downey

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Missouri
I was at a building that we finished a couple years ago that the following happened.

During a storm around 2:00 AM there was a loud clap of thunder and lightning which appeared to be very near the facility (there does not appear to be any physical lightning damage to the structure). Just after the lightning the 1000A 480/277V 3 Phase main breaker tripped and the generator did not start.

Review of the generator found that multiple circuit boards had been fried. I am waiting on a response from the generator manufacturer on the cause.

There is an internal TVSS unit which shows on its counter that it has not been hit and all of the LED indicator lights are on.

There is not a Lightning protection system on the building.

What are some possible causes to make the 1000A Main breaker trip?

-Ed
 
This has been discussed here a few times before, but some of the possible causes:

  • EMF pulse from the lightning strike;
  • Surge caused by the lightning (very likely since you had boards fried, BTW have the electronic trip unit on that breaker tested ASAP as it may be damaged);
  • Sag in utility voltage which caused a current spike as it recovered;
  • Undervoltage trip during that sag, if breaker set for undervoltage trip;
  • Phase loss during event, with phase loss protection trip;
  • And the very strong possibility that something got damaged and the fault self-cleared.

You have some investigating to do before you can say with some assurance that it was one or more of the first five in the list that caused the trip.

A 1000 amp main tripping is not to be taken lightly, and I sure would not have wanted to be the one resetting it after that event.
 
mxslick said:
A 1000 amp main tripping is not to be taken lightly, and I sure would not have wanted to be the one resetting it after that event.
Click to expand...

A long while back I had a large breaker on an end user's MCC that would trip now and then. It turned out rats were living in the MCC and every now and then one would complete the circuit across the bus bars.

it seemed to happen during rain and snow storms. I think the rats came inside the MCC to seek shelter from the rain and snow and get warm.
 
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Hit the ground first?

Hit the ground first?

It's possible the strike hit the ground first and elevated the immediate ground, earth, potential voltage. If the strike hit within 25 to 50 ft of the service entrance or an outside generator, it may have travelled through the earth and retained enough energy to be picked up by the service or generator ground and neutral. The ground or neutral could have been the path in for a momentary transient.

Was there enough energy to burn and scorch the circuit boards, or just enough to blow sensitive chips and the foils on the board? Phones get hit also?
 
GFP could result in a trip due to a current surge on the ground for the system.
Phase failure due to possible utility issues.
Damaged equipment downstream from the lightning strike?
Did the counter change from before the trip or is this unknown?
 
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