[TowerTalk] Pole Pig Transformer wiring

[Tom Rauch]

> Jim Lux wrote:
> >> The power company also grounds the
> >>neutral connection at the transformer to earth ground.
> >
> >Not necessarily.. for the same reason as you have a
single interconnect
> >between neutral and ground.  You don't want neutral
return currents
> >flowing back to the transformer via the ground path.

Ian Replied:
> Interesting... the power companies in the UK take a
different view. In
> the event of a neutral break in their local distribution
system (230V
> single-phase, neutral close to earth potential) they'd
rather have the
> return current flowing back through earth than create a
shock hazard due
> to the neutral becoming hot.
>
> Therefore they almost always earth the neutral at the
transformer,
> and/or anyplace else they conveniently can.

I had a look at the transformer here.

I have two drops. One to a distribution pole with a meter
and a pair of dual 200 amp mains that feeds my radio room
and all the outbuildings, the other drop feeds a single 200A
dual mains for the normal house wiring.

At the transformer the heavy neutrals bond directly with
very heavy wire to the bare distribution ground wire passing
the pole. The center tap of the pole pig has what looks like
a number 6 solid copper wire to the metal can and to the
ground wire running down the pole. That ground wire bonds to
the neutral wire running down the street.

The ground path at the pole is from the 240V winding CT to
earth and to the HV neutral at the road through a small
gauge wire, perhaps number 6 AWG. The heavy bonding is from
the bare triplex drop wire directly to the street neutral,
which is the return for the 7,200 volt distribution line.

Very clearly the utility wants the major bond to be with the
7200 volt return, a much smaller conductor goes from the pig
CT to the pole ground wire...which eventually after a few
splices connects to the area distribution neutral.

What do others see outside their houses in the USA?

73 Tom