is bus duct damage?

[charlie tuna]

i have a customer who called friday about a power outage on a 2000 amp g.e. bus duct (480 volt). a security vender was working in an electrical room and somehow(???) got a piece of tie wire into that tiny hole in the torque nut and caused a blowup! it burnt his hand-arm and the side of his face--not bad--similar to sunburn. tells me he had to be on his hands and knees since the hole is about two foot above the floor. he had no reason to use tie wire in the job he was doing, but there was a basket stored in this electric room that had a pack of galvanized tie wire in it. the load on this bus is light to moderate since it feeds emergency power. my question is this:

very little exterior damage is present on the outside of the bus--but it blew all three 1600 amp fuses! since it is in the area of the torque bolt the buses are shaped with "u" holes at the joint. my theory is "the wire caused a phase to phase flash which jumped to all three uninsulated areas within that "u" joint" and blew itself clear"? they replaced the fuses and put the bus back "on line" with no problems. but i'm considering the amount of current required to blow three 1600 amp fuses in a flash must have done some damage to the joint area. luckely enough this is a filler piece and only four feet long and fairly accessible. i think it might be wise to order this replacement section for building stock? what do you think?

 

[ron]

Re: is bus duct damage?

If nothing else, perform a Megger insulation test (doesn't have to be Megger), on all phases to neutral and ground.

 

[brian john]

Re: is bus duct damage?

Meggering at 1000VDC with the neutral isolated

as stated pahse to phase, phases to neutral and all four conductors to ground it may be wise to inspect the joint (was not sure about the true exrent of the damage. In addition you could do a DLRO (digital low resistance ohm meter)test across the de-energized bus joint.

 

[rbalex]

Re: is bus duct damage?

Since its back in service and apparently working, I would recommend a thermographic check if you have the equipment or service available to you.

I'd recommend doing the check along the entire bus run too. Depending on the type of construction, meggering may not reveal damage to internal bracing or other joints not immediately involved with the incident.