Re: Z-Machine Sparkage - Substation Fault

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Dave and all

Unfortunately, I don't have any more information on this particular fault. 
The MPEG was used as part of a local power company safety program, but 
their program manager didn't have further info.

I agree with Terry that it was most likely a LV side phase-to-ground short 
that failed to clear for some reason. The fault current was still more than 
adequate to really fry the substation transformer. A phase-to-phase fault 
would have been cleared fairly quickly (one way or another!). An equipment 
failure is a possibility (such as insulation failure on a CT that did 
current sensing for an Oil Circuit Breaker (OCB)). While it could have been 
some sort of sabotage as Steve suggests, a wild animal is also quite likely.

About 10 years ago we had a massive local power outage at about 10:00 PM. 
My family and I were about 30 miles away in the country watching the 
Persied Meteor Showers on a beautifully clear night. Suddenly the lower 
part of the sky lit up with what looked like the welding arc from Hell, 
lasting perhaps 2-3 seconds. When we drove back home, the power was out in 
an area about 5 miles on a side.

A fellow engineer and friend lived about 1/4 mile from where the problem 
had originated - in a 345 kV Com Ed substation. He also happened to be 
outside watching the meteor shower when night suddenly turned into day. He 
saw a huge looping blue-white arc coming up from the substation, and heard 
a loud buzzing roar, ending with an even more brilliant flash and a huge 
bang. Everything went dark in the neighborhood. He began walking over to 
the substation, arriving just about the time that the fire department, 
police, and Com Ed folks also converged on the site.

After considerable inspection, the power company folks concluded that the 
substation and equipment were apparently unharmed (save blackening in the 
area near the arc,) and they turned the power back on about 3 hours later. 
However, it wasn't clear just what had triggered the problem in the first 
place.

Further inspections the next day pinpointed the cause. A raccoon had 
apparently made its way into the substation and had created a 
phase-to-ground fault by climbing up one of the station's 345 kV bushings. 
They were able to "piece together" the chain of events when they found a 
tiny piece of the raccoon - the very tip of its tail... the rest had been 
vaporized.

Because of so many nuisance outages from squirrels, most transformer 
bushings in our area now have plastic covers that shield the tops of the 
transformer bushings. I've personally witnessed a squirrel getting 
vaporized when he bridged a bushing in the substation that supplied our 
building complex. Made one heck of a bang, but it didn't trip any breakers.

Best regards and play safely,

-- Bert --
-- 
--------------------------------------------------
Out-of-Print Physics and Engineering Books and
coins shrunk by ultrastrong electromagnetic fields!
Stoneridge Engineering: http://www.teslamania-dot-com
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Tesla list wrote:
 > Original poster: "David Sharpe by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>
 >
 > Hi Bert!
 >
 > Tesla list wrote:
 >
<SNIP>
 >
 > Bert, any further information on the initial cause of that substation
 > fault?  Great
 > find!
 >
 > Best Regards
 > Dave Sharpe, TCBOR
 > Chesterfield, VA. USA