Intentionally vague question.

Any thoughts on transformer failure?

odin wrote:

You mean, besides squirrels?
Insulator failure.
PCB breakdown due to heat.

"odin" <[Only registered users see links. ]> wrote in message
news:hoqdnecGRMQyDAnenZ2dnUVZ_tOdnZ2d@whidbeytel.c om...

Perhaps all the cooling oil leaked out.

> PCB breakdown due to heat.


Yes. besides 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. 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, 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.
I could not believe that he was on his own. if he was hurt, he would be on
his own.


The explosion was in the transformer. It has been there for a few decades.
Why now? What is the typical failure mode?


PCBs are all removed from Vancouver of 1972.

odin wrote:

Which shows two instances of poor judgment on his part.
1) working without a partner
2) replacing a one-time fuse before checking for a reason for the fuse
to blow.


It could have been a gradual deterioration. Insulation cracks can be
caused by cosmic ray irradiation (see the darkening of plexiglass
windows), and the heat in the transformer plus mechanical vibration can
gradually exacerbate them. The fuse probably did its job just as the
current started to spike, but not before doing additional damage, which
is what caused the explosion before the second fuse could blow.


Cooling oil additives, then. Heat and strong local fields can
accelerate a host of organic chemical reactions.

PD

> Which shows two instances of poor judgment on his part.

I asked him about that. He said it was BCX hydro policy... (cost cutting???)



I thought the same thing. I would have disconnected the transformer and
replaced it. Perghaps putting the old one up for refurbishment.... Cost
cuytting policy in effect????


Yes! That is what I want to know. how does insulation fail? It was clearly a
short circuit. What I want to know is what are the failure modes of a 27 KVA
to houshold single phase polemount stepdown transformer. Is it a loss of
oil? I saw a lot of oil dripping on fire.

Pauls' Axiom # 13 ...

If Man Made it ... It will break...


"odin" <[Only registered users see links. ]> wrote in message
news:hoqdnecGRMQyDAnenZ2dnUVZ_tOdnZ2d@whidbeytel.c om...

"odin" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...

fuse.
are
partner.

Just an idea - if the container had rusted enough over the years to let a
little H2O in, that would account for the initial shorting of the fuse *and*
later the explosion what it boiled from the heat, bursting the can like an
old-time steam boiler and spewing hot (and flammable) transformer oil.

Bit I'm just a chemist. I would suggest you ask a lineman for the power
company.


Tom Davidson
Richmond, VA

tadchem wrote:


Hope it wasn't PCB enriched oil!

Double-A

"odin" <[Only registered users see links. ]> wrote in message
news:hoqdnecGRMQyDAnenZ2dnUVZ_tOdnZ2d@whidbeytel.c om...

If you ask on alt.engineering.electrical there are a number of power /
utility types who might be able to give you some.

j