Utility/Bomb Company

Its summer again and every summer with the high electrical demand, there are stories of "Exploding tranformers." I could easily understand if overstressed transformers melted, but why would they explode? Are they being cooled chernobyl-syle with something flamable?

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[Insert Clever Quote Here]

I've always thought that when a tranformer "blew up" it was because it short circuited. This usually seems to happen when the transformers are physically disturbed by acts of man or God such as weather, earthquakes, or just some idiot driving his car into a utility pole.

falcon2 asks:

I could easily understand if overstressed transformers melted, but why would they explode? Are they being cooled chernobyl-syle with something flamable?

Yep, mineral oil.


Now, pacePapaBear, it may be that what is described is actually a more-or-less spectacular electrical breakdown (I have never been, and hope never to be, close enough to an "exploding" transformer to tell the difference). But, regardless of whether the mineral oil is involved, it's there.

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"Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away."

I've seen about a half dozen or so transformers that have "blown up" so to speak. Two were from lightning strikes (gee, I wonder why they went boom), three were from vehicles striking the poles with the transformer on them, and one was from a squirrel that was dumb enough to jump on the contacts at the top of the transformer. We normally get a call for a transformer explosion. When we arrive the top of the pole is on fire, sometimes the cap off of the top of the transformer is on the ground somewhere. We have a good picture of a transformer in mid-boom at the station, I'll try to get it scanned soon.


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Jeremy....

I can think of no more stirring symbol of man's humanity to man than a fire engine - Kurt Vonnegut

My guess would be that when a transformer shorts out, the high voltages involved would cause an electrical arc. This would quickly heat the air inside the case, causing a rapid expansion and a loud bang, exactly like a small lightning bolt.

At a summer job several years ago, a tansformer blew early one morning. One co-worker who was driving (it was still dark) said that the sky suddenly flashed blue and there was the sound of an explosion. According to the power company, one the transformer's three phases failed. I wish I had seen it.

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"I had a feeling that in Hell there would be mushrooms." -The Secret of Monkey Island

If a sealed transformer develops an internal fault, with resultant arcing ,the byproduct of the arc in the cooling oil is a form of acetylene.

So-----arc plus acetylene=BOOM.