On Tuesday, November 26, 2013 2:20:23 AM UTC-5, nestork wrote:
Tony Hwang;3155652 Wrote:



You are trying to say if I and V is out of phase by certain degree

there will be a current flow which is wasteful. That current does not

do any work. That is why in big industrial site or buildings use power

factor correction device.



No, houses very rarely have power factor correction. Most of the reason

why is that electrical utilities only charge their residential customers

on the actual kilowatts they used, not the KVA the consumed. So, why

have power factor correction if it's not going to save you any money on

your electric bill?



I'm saying that in the real life situation, electrical loads being

carried by L1 and L2 are rarely ever going to be perfectly balanced.

The result is always going to be some timing differences in the current

sine waves travelling in the white wires returning to the electrical

panel. The result is going to be a "net current sine wave" as a result

of superposition of all the individual current sine waves in the neutral

buss in the main panel.



You can't have current without voltage. Ergo, there is always going to

be some net voltage sine wave in that neutral buss, and therefore in the

ground wire cable coming out of the main panel.

Usually there is going to be some current flow, specifically the
unbalanced portion. But if the only loads on are 240V, eg oven
and water heater, then you would have zero current flow in the
neutral. Or if you had that and you put two 100W 120V light bulbs,
one on each leg/phase, then again you'd have zero current flow in
the neutral.




So, how can you NOT

have current into and out of the Good Earth through the grounding rod or

pipe if there is a voltage imposed on that grounding cable by the white

buss?


Yes, if there is current flow in the neutral, then some smaller portion
of that current will flow through the earth, back to the transformer.
It will divide according to the impedance of the neutral vs the impedance
of the earth. The neutral is going to have a lot less impedance, hence
most of the current is going that way. Also, that current is incidental,
it's *not* the primary path and it's not being relied on to deliver power.
THAT last part is what Danny doesn't get.



I'm not saying that current flows back to the generating station through

the ground. Or, at least, I'm not saying that yet.



Thank God.




I'm saying that electrical loads are rarely going to be perfectly

balanced, and any imbalance in the impedance of electrical loads is

going to cause timing differences in the amperage sine waves carried by

the white wires connected to the neutral buss in the main panel. That

means there HAS TO BE some net voltage sine wave in that neutral buss to

drive that net current sine wave.



Generally correct, except for the timing difference part. Assuming
pure resistance loads, there are no timing difference in the various
loads. And adding power factor, which would get you timing differences,
would only obfuscate the issue.




And, I can't see why a net voltage sine wave in the neutral buss

wouldn't cause current flow into and out of the Good Earth at the

grounding rod or plumbing pipe.



If the loads aren't balanced, then yes a small portion of that
unbalanced current is going to flow back to the transformer via
earth. The vast majority of it is going to flow back via the
lower impedance neutral.




And, according to one of the pictures posted by G. Fretwell, the current

measured through his grounding rod is 0.142 amps. And that's without

any intentional effort to imbalance the electrical load at the main

panel.



Where am I wrong there?



You've basically got it correct. The big disagreement with Danny is
that he's insisting that the power company uses the earth as a
return conductor to deliver power. That's what is wrong. In the
..142 amps example, it's an insignificant part of the power.