On 3/29/2009 5:34 PM Malcolm Hoar spake thus:

In article m,
David Nebenzahl wrote:

And really, how else could a transformer fail spectacularly, other
than an overload, except by there being some kind of massive
overvoltage surge (what people incorrectly call a "power surge")?

Actually, transformer cores do "wear out". And when then do,
they do overheat which can lead to spontaneous fire/explosion.

However, if multiple transformers failed in the same area
there was clearly some precipitating event. Most likely
a lighting strike but there are many other potential causes.

Absolutely clear weather all around. So it must have been some kind of
cascading failure, and once again, I say the only way transformers can
blow up under such circumstances has to be overvoltage.

Fortunately, it's rare to experience the kinds of fluctuating
voltages you observed. The system is generally designed to
deliver a relatively clean supply or none at all. And it
does work that way most of time.

And how do you know this for sure? Have you monitored your line voltage
during an outage? Could yield some interesting results ...


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