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What happened?

No squirrels. I went for a drive yesterday up into Canada for a hike up Grouse Mountain. I do that about every month with my girlfriend north of the boarder in Vancouver. I was at her house in Shaughnessy (posh part of Vancouver) and I heard a pop that sounded like gunfire. The lights went out. I went outside looking for what was going on. Then a BC hydro truck came up and parked under a transformer by the house. I watched him replace a fuse. When he reconnected it, a huge explosion happened in the transformer (we are talking Hollywood pyrotechnics here). I thought he was killed or hurt, as he was about two feet from the biggest explosion I ever saw. He was dazed. He eventually came down and I talked with him. He thought the problem was in the fuse, not the transformer. He was wrong. He was on his own, no partner. Question: what happened?

Reply to
odin
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Sorry... that post was intended for alt.engineering.electrical

Reply to
odin

The fuse blew because of a fault. It is likely that there was an internal fault in the transformer.

Charles Perry P.E.

Reply to
Charles Perry

The transformer was turned on when he placed the fuse and he experienced a power surge or an arc?

Reply to
Billy H

In my back yard, I have a pole with underground feeders for some city buildings. These are protected by those pole top expulsion fuses. When one of those goes off, it is like a cannon. The utility company always tries a new fuse first. In a couple cases I watched them install a new fuse and it blew as soon as he swung the contacts closed. Next, they go off and find the fault.

John

Reply to
JohnR66

If this is one of those, "What happened next?" questions - presumably he went home and changed his trousers and pencilled in some replacement eyebrows.

If you mean, "Why didn't he do more tests before powering up?" I guess because that was what he had been trained to do.

We lose a fuse on our local low voltage distribution, here in the Dartmoor National Park, once or twice a year. It is presumably lighning or something - the lines go across open moorland. Why it *always* seems to be the red phase - which I get to my house, is a different matter (UK houses usually have a single phase supply). Seeing the flash marks on the tabs of the old fuses discarded at the base of the pole - I guess they shove the replacement in and/or pull them out "live". Anyhow, the point being that, so far, it has always been the fuse and the transformer has been fine.

If you mean, "What happened in the transformer?" I guess the insulation failed in a medium/big way and blew the original fuse. When power was re-applied, a whole bucket load of amps went through the failed bit and vapourised it and some of the stuff around it. The other bits of the transformer and the surrounding air couldn't get out of the way fast enough - so the pressure grew until they could move pretty quickly.

Rather him than me - I used to hate working on live circuits, even on lv. I knew the theory but never quite believed it.

== Sue

Reply to
Palindr☻me

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