On Thu, 22 Sep 2005 08:52:34 -0400, Pat Coghlan
wrote:

On a hydro pole, there are always 3 wires...at least in Canada. The 3rd
wire is neutral, going back to the substation, isn't it?

Why is that 3rd wire there if neutral is simply tied to ground at the
panel. This would seem to obviate the need for that 3rd transmission wire.

-Pat

Bill wrote:

An electrical appliance with a metal case can "malfunction" and cause the
metal case to become "energized".

To prevent you from being electrocuited in this situation, the metal case is
"grounded" using a separate ground wire.

Now if you were to instead use the neutral wire for grounding, and then the
neutral wire came loose anywhere between the appliance and the breaker
panel, and then you "turned on" the appliance, the metal case would then
become "energized' as the hot wire current would travel from the hot wire,
through the switch, to the neutral wire, then back up through the ground
wire to the metal case.

Turning on the appliance switch would have the effect of connecting the
metal case of the appliance to the hot wire in this situation!

So *always* use a separate ground wire - never connect a ground to neutral
(except at the panel of course).