According to HA HA Budys Here :
From: "new"
The current in my ground wire as I understand it resulted from the current
going through either of the two hot legs of the 220 to the neutral in the
circuit box that is attached to the neutral coming in from the pole. As
this was cut, the current instead flowed to the ground rod outside (the box
is also grounded to the plumbing system).
My question is: I guess neutral and ground are joined on the neutral bar in
the circuit box. Why goes not the current always flow to ground? WHat am
I forgetting from my ancient BSEE degree?
You're also forgetting, utilities don't deal with "neutrals" in the sense that
inside wiremen do - for a utility system there is no "neutral," they call that
conductor just ground. It only becomes a neutral after it has joined with your
ground rod in your main panel.
Taking the terms in the standards literally, it's the reverse of that. Neutrals
are effectively the "centre reference" of a multiple wire circuit. Ie: three
phase. Ie: the neutral of the 220 split phase circuit that's your house feed.
"Real" Neutrals aren't necessarily anywhere _near_ ground.
Technically, for example, a 120V circuit cannot have a neutral because it's
not a multi-wire circuit.
Once the neutral comes to your panel, it becomes the "grounded conductor" because
it's connected to ground. As contrasted with the "grounding conductor"
(safety ground).
The electrical codes (both NEC and CEC) very specifically uses the "grounded
conductor" term instead of "neutral" for the white wiring in your house.
However, the home building trade uses the word neutral. So do most others, despite
the fact that the terminology isn't technically accurate.
[There's a longer explanation in the electrical wiring FAQ which specifically
uses "neutral" to be consistent with the majority of usage, and make it very
difficult to confuse it with "grounding conductor"]
The current doesn't normally just go to ground (from your panel's neutral buss
bar to your grounding rod and/or water main) because it's easier, and usually a
shorter trip, to get back to exactly where it came from (the utility's
transformer, where their "neutral," - the center tap) via the guy wire.
"shorter trip", being short form for "lowest resistance".
Most people tend to think that grounding rods and the like have very
low resistance (as in zero). They do not. The grounding-rod to dirt resistance
can be surprisingly high. For example, a NEC-satisfactory grounding system
can have _more_ than 25 ohms to dirt. A dead-short to dirt could
only push 5A or so at 120V. Not even enough to trip the breaker.
Grounding systems aren't supposed to carry current. They're really only
a secondary way to keep the power from drifting too far away from a dirt
reference. Neutral current (the imbalance between the currents of the two
hot wires) is _supposed_ to go down the real neutral wire back to the
transformer.
Trying to make the dirt be a conductor can lead to all sorts of problems -
highly variable voltage (especially under variable loads), electrical
shocks from standing on the dirt, setting the grass on fire. Etc.
If you see appreciable current flow in the grounding conductor, it almost
always means that there's something wrong with the neutral. Which implies
the "loose neutral" syndrome, where you can get wild voltage swings on 120V
circuits. Including up to 220V...
Or then again, since you can't tell which way the AC is flowing on your 5.5 amp
reading, perhaps it's your neighbor who has a bad neutral...
Unlikely. The range is relatively short, and you're only getting "side
effects" of a situation which'd be _far_ worse in the neighbor's. Ie:
exploding TV sets. Ie: high voltages on grounded appliance cases or
plumbing.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.