Re: grounding hooks, etc. was:electrocution experiences

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Grounding devices (hot sticks,etc.) are designed to be hooked on a circuit
that ISN'T live, to make sure they stay that way.  The idea is you open the
circuit (discharge any stored energy in bleeders, etc.), hook up the
grounding device, then go to work. If some idiot turns the power back on, or
there's a transient (lightning, switching surge) that would cause a voltage
to be induced, the grounding lead keeps the wire or gear you're working on
at a reasonably safe potential.  The same would apply for safety on filter
capacitors with bleeders.  Ideally, the bleeders have already done away with
the charge, but the stick is just to make sure.  A typical personal
grounding rod will often have a holster or hook of some sort that has a
microswitch in the interlock circuitry, so that if the stick isn't in its
"parking spot", you can't turn on the HV.

Discharging a big cap with a low impedance load is a good way to break
parts.  Most personal grounding rods have a #10 or #12 wire, which if you
hooked it up to a big enough capacitor would make a fine exploding wire.

Discharge rods made for discharging capacitors (e.g. in a transmitter power
supply) have a big (Physically, not resistance wise) resistor that can
safely absorb all the stored energy.  Typically, the resistor is a few K
ohms, to limit the discharge current to a few amps.

A straight insulated rod (aka a hot stick) is used to actuate something live
(like one of those knife switches on a power pole) or to put a probe near or
on energized lines.  They are also made as a sort of extended HV probe with
a volt meter built in.


> Original poster: "Kevin Ottalini by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ottalini-at-mindspring-dot-com>
>
> All:
>         Mechanical crowbars, discharge sticks (or "Jesus Sticks" as they
> are sometimes known) are used by the local PG&E linemen (& women).
>
> I was quite lucky to pick up surplus a fixed-facility discharge stick.
The
> handle is made of Teflon and is quite heavy!
>
> I scanned in the small chart attached and cleaned it up a bit ...
> you can find pictures of it on my starter Safety page:
>     http://www.mindspring-dot-com/~ottalini/Safety.htm
>
> (The cleaned-up graph should be logx-logy scales  ... but word
> doesn't do that easily! I'll clean it up a little later).
>
> Personally, I wouldn't want to discharge 30uFd at 20kV without
> a large safety shield between me and the cap!  (but our
> quarter-shrinker friends ALL know what happens, don't they!!)
>
> Kevin
>
>