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One finds electrical reports where a little slip-up evolved into a big problem.

In utility systems there are typically fat 125-volt battery sets {or sometimes 48 or 250V} that take care of transmission and distribution circuit-breaker tripping, so that AC can go away for whatever reason, and still be able to trip circuit breakers. [This is sorta' like AC-operated shunt-trip circuit breakers on building mains and exhaust fans discussed at E-C.net, but with DC-powered solenoids for dumping stored hydraulic pressure to part some big contacts.]

There are components that decide if breakers should be open or closed, that can get a bit complicated from a control-wiring point of view. Normally there are many thousands of feet of 14AWG wiring to interconnect all this stuff.

When this incident happened, it must have been absolutely mortifying to hear 15 high-voltage breakers opening at once. [They literally shake the ground in the process.] Very likely it took one slip of a screwdriver or a misapplied wire to initiate a seven-hour outage of 290,000 customers.

That would have spoiled my Tuesday. smirk smirk




[This message has been edited by Bjarney (edited 05-23-2003).]