Post by thread:Re: [OT]Village Electrical Supply suddenly rise to

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 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 -- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available!

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.