SV: SV: [CAD_CAM_EDM_DRO] Delta 3 Phase fault finding

Normaly this is no problem, because you have to have a earth fault switch in
your fuse box. This wil tripp off if currents in exces of 10 mA or so is
being drawn to ground.

The real danger is normal houses whitout 3-phase. They are just hooked up to
two of the phases. I have actually measured 120 volts from power earth til
cable TV earth, and also betwen my first mill and the concreet floor (i had
isolation between them) it was standing on. This was because of a faulty
washing machine or something in a neigboughs house. There wasn't even
anything they could do about it exept to notify my neibough and ask them to
get it fixed. They told me that it wasn't anny of their busines to actually
fix it.

Anders Blix

> From: wanliker@...
>
> In a message dated 3/10/00 7:51:08 AM Mountain Standard Time,
> anders.blix@... writes:
>
> << If you ask for 3-phase you get earth allong as wel. But you are not
> allowed to connect something betwen one phase and earth. I think this
> have
> something to do wit why it is so easy to get 3-phase installed.
> >>
> We used this system in the copper mines where we worked, the big danger
> was
> if one phase became grounded two things happened. The other two phases
> went
> to very high voltages with reference to ground, electrical shock hazard,
> and
> harder on insulation. But the bigger danger is one phase was shorted to
> ground, at a given location, and another phase shorted to ground at
> another
> location, fuses would blow, and equipment would go off line, and sometimes
>
> damage equipment. One of the things we did was to monitor the phases to
> ground with a series string of light bulbs, from each phase to ground, we
> used three 120 volt lamps in series for a 220 volt circuit, per phase for
> a
> total of 9 lamps. If all was well they would just glow dimly, if there was
> a
> fault on a phase, one string would go out, and the other two would glow
> brighter. This way we could turn off equipment to isolate the faulty
> equipment, before the problem became a big one, shut off the faulty
> equipment
> and the lamps would return to normal. Higher resistance and intermittent
> faults would show clearly as the bulb strings would blink, and again show
> you
> that there was a problem. I would highly recommend this kind of status
> board
> for any 3 phase Delta equipped shop,
>