On Friday, November 22, 2013 6:17:08 PM UTC-5, John G wrote:
Danny D'Amico was thinking very hard :
On Mon, 18 Nov 2013 18:09:29 +0100, nestork wrote:
This web site explains it fairly well:
http://tinyurl.com/y4syno6
That was interesting.
Notice the 7200V primary side of the transformer didn't look
grounded in the picture (but it must have been). Right?
Also, the ground (literally) was stated as being part of the
circuit (although I would have like them to complete the circuit
at your lamp, and then *back* to the power company (via the
ground).
If you had any understanding of electricity you could understand that
the GROUND is not part of the circuit.
It is there to keep all the parts of the system at the same reference
potential.
A 3 phase Delta system requires only 3 wires.
A 3 phase Wye system has 4 wires to allow connection to the center
point and one phase to get a lower voltage than that between any 2
phases but a symetrical 3 phase load of the correct voltage only needs
3 wires.
The ground is only for safety and is, by code, connected to the neutral
at each customer.
The USA system delivers only ONE 240 volt supply to houses and the
neutral is really only a centre tap of that to get 120 volts for small
appliances.
I know there are variations (too complicated to explain here) but the
overall principle remains.
The ground wire plays no part in a proper fault free system.
No current flows in around or thru the ground if all the conductors are
installed to code. :-Z
--
John G
I agree with 99% of the above, except the last sentence. You will
have some very small portion of the current flowing through the ground.
Take for example the simple case of the neutral and ground of a 240/120V
service being tied together at the house and at the transformer. Those
are two paths for current to flow, just like two resistors in parallel.
The vast majority of the current will flow in the neutral conductor because of
it's low resistance. Some small amount, however will flow in the ground path, with it's higher resistance.