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'[OT]Village Electrical Supply suddenly rise to 600'
2007\08\06@073409 by jtroxas

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I remember in the news during a hot summer day some folks died of
electricution.. village appliences were all fried when supply voltage
suddenly rise to more than 600v.. Investigator blamed it on the dry ground..
beneath an electrical Post carying a large transformer... Apparently they
said the dry ground insulated the grounding...

How can this happen?? Are we at risk of electricution this days were drought
is common???



2007\08\06@104415 by Harold Hallikainen

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> I remember in the news during a hot summer day some folks died of
> electricution.. village appliences were all fried when supply voltage
> suddenly rise to more than 600v.. Investigator blamed it on the dry
> ground..
> beneath an electrical Post carying a large transformer... Apparently they
> said the dry ground insulated the grounding...
>
> How can this happen?? Are we at risk of electricution this days were
> drought
> is common???
>
>


I'm going to guess that they ended up with a high common mode voltage
instead of differential voltage. For example, here in the US, residential
power is 240VAC with the center grounded. Most appliances operate between
one side of the line and the center tap (neutral), though some larger
appliances may operate between the two lines (240VAC). This voltage is
derived from a transformer secondary with the center tap grounded. The
transformer primary is driven by several thousand volts. I can imagine
that if the center of the secondary were not grounded, the capacity
between primary and secondary could pull the secondary common mode voltage
hundreds or thousands of volts above ground. In the US, though, the
neutral is grounded at each home, so there is some redundancy. If the
ground is poor at one home, it's better at another, holding the
transformer secondary close to ground.

Harold



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2007\08\06@112011 by David VanHorn

picon face
I'd bet that "dry ground" was not the real problem.


The split transformer approach here in the US explains the phenomenon
of light bulbs that blow quickly in particular sockets.  A heavy load
on the A side gives more voltage on the B side, and light bulbs have a
very nasty lifetime/voltage slope.

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