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Originally posted by Kitsune
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Anyone know if there is any truth to the old wive's tale (old man's tale?) of touching potentially live wires with the back of your hand? The idea, from what I've heard, is that if there is current flowing your muscles will jump and pull your arm away from it instead of grabbing the wire.
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Here's the deal... the reason you are supposed to use the back of your hand is not so much that you'll be repelled, that's a 50:50 thing<G>, but if your muscles do contract, at least you won't be grabbing the live wire.
I know that most sane people don't work on live circuits by choice, but consider this, if you work on a live circuit, and you do something stupid, you'll know instantly from the loud crack the subsequent loss of potential when the breaker trips. I almost always work on household circuits live for just that reason.
As far as telephone stuff goes, plain old telephone service is -48Vdc to -52Vdc, but can only deliver a few milliamps before various protective devices fire. ISDN, T1, and the like however run at -130Vdc, and can deliver quite a bit more current. I learned this when a telco guy mismarked a demarc point<G>!
As far as really high voltage stuff goes... the coolest thing I ever saw was a chain dropped across two phases of a 500KV circuit. I worked for the power company at the time, and we were testing our own protective systems. Two bucket trucks, one on either side of the line, and each guy holding one end of this big assed chain (I missed the part where they got the chain from one bucket to the other... I'd have really liked to see that!!!) On the count of three they drop the chain, and if causes a fault... but it also mysteriously disappears.
At the time we witnesses were all standing on rubber mats with out feet touching... anyone want to explain why?