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Discuss Ka-boom in the UK Electrical Forum area at ElectriciansForums.net
What voltage? They look like 3.3KV fuses but the wiring doesn’t. Interesting how you can see the flashover points on the fuses. Is the white mark across the back plane tracking?
I’ve not seen anything like that for many years, nothing to do with lightning but inductive discharge when a motor stopped.
The motor had been uprated three times as I can remember, pity the draw out starter hadn’t. The fuses had gone up from 150A to 300A, obviously the fuse diameter was bigger making the gap between them far to small.
Intermittently when the motor stopped the back EMF would cause flashover taking out the 600A busbar riser fuses.
I wasn’t based on this plant but got lumbered with finding a cure. I fitted insulating shields between the fuses and everything was fine.
It ran like that for a couple of years and then the problem started again? Some pillock had replaced the nylon nuts and setscrews with brass! To make it even better they’d cut the setscrews with pliers leaving a nice point aimed directly at the adjacent fuse. It was just like a spark gap used for MV over voltage protection.
Our plants took several direct strikes but they never did any damage, the building acting as a Faraday cage.
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