Working around high voltages?

[Multi-Volti]

Not necessarily in order of importance...

Some say never work on energized equipment, ever. Sometimes you may feel
like you have to, or really do have to.

Some advise never working alone. Have someone in the room who knows what to
do just in case.

One rule is keep on hand in your pocket while doing with the other, thus
preventing current flow across your chest, and thus your heart.

Another is if you anticipate having to touch something (don't assume the
chassis is at ground potential, or that the chasses of two pieces of gear
are both at the same potential...I have seen and experienced 80 vac between
two chasses not connected together), keep your hand so that the back of it
(ie, back of fingers) comes in contact with the conductor rather than the
front. The reason for this is electrical shock tends to contract muscles,
and you want your hand to close reflexively to pull the fingers away from an
accidental contact, rather than close around the conductor. To illustrate
this, with an open hand, place the back of your fingers against a pencil.
Now make a fist. Your fingers move away from the pencil if I've done a good
job explaining.
Now place the front (palm side) of your fingers against the pencil and make
a fist...see, now you're 'toast', or 'bacon', as the case may be for hams (a
joke, not talking about appearances!).

Beware of capacitances recharging due to dielectric absorption (DA) or other
effects. If power is off, placing a grounding jumper from the hv terminal to
ground and keeping it connected that way will keep the hv from 'coming back'
Remember to check continuity of your jumper before using it and remember to
remove it (!!!) before turning the power back on!

Double, no, triple check power cords are unplugged when you want them to be
before working on gear.

Rubber gloves? I guess I wouldn't take risks that involved depending on
them. I think electricians use them when they have to work on live
conductors but have them officially tested regularly for voids/pinholes,
etc.

I once saw a news feature about how 'prophylactics' were 'electronically
tested'...pretty weird trivia...that's another story, not for here.
Basically the, uh, test fixture depended upon detection of insulation
failure similar to the gloves above.

Murray


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