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Re: Electrical Wire unSafety



Since some people are still reading postings under this heading, I'd
like to tell you about something interesting that happened here
yesterday afternoon.

Just after school was out (3:15) my daughter called me from home and
said she heard a loud explosion and the lights went out.

I hopped on my bicycle and headed home, choosing the path that I knew
went by some of the telephone poles that feed the HV to the transformer
by my house. I live on the edges of campus. Just as I was getting to
the edge of campus I came across a telephone pole that was one fire. It
was a three-phase pole. The top three feet had broken off and that
section was hanging by the three HV phases which had twisted across each
other. The new top of the pole was burning as was the portion that was
hanging.

When the power company trucks arrived, we just stood around for a while
trying to speculate what had happened. The final conclusion was that an
insulator had partially failed. It did not fail enough to blow out that
phase at the nearest circuit breaker, but it failed enough to get hot
and start the pole on fire. The pole probably burned for some time,
eventually getting weak enough that the tension in the wires snapped it
off at the weakest part of the burning area. Once it snapped off and
began falling, the phases crossed and that was the explosion my daughter
heard.

The circuit breakers tripped clear back at a substation, so a
significant portion of my community lost power. This pole was a "side
spur" so the work crew cut the feed wires to that pole, then closed the
breakers, restoring power to the whole community except for the college
dormitory that was powered by that pole. Then they made a nice cut at
the top of the pole with a chain saw, attached a new cross piece,
restrung the HV cables on a pole that was now a few feet shorter. They
said they might replace the pole in the summer.

Then they reconnected the feed to that pole live. That was the most
interesting part to watch. Two guys in a bucket reattached the wires to
the hot HV. By this time it was dark, it was snowing lightly, it was
cold. These guys are a lot more brave than I am. At some times their
heads and shoulders were high enough to be between two of the phases,
which appeared to me to be about 3 feet apart. The top of the
fiberglass bucket was just below the phases. They were using various
tools. They talked to each other, but not small talk... they only
talked about the job they were doing. I was impressed how they seemed
to automatically work in a manner in which they never touched anything
(other than the bucket) at the same time they were touching one of the
phases. I suppose this becomes rote at some point, but it sure seems
hazardous to me.


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Bluffton College
Bluffton, OH 45817
(419)-358-3270
edmiston@bluffton.edu