To drain off any stray charges and maintain the AC common-mode voltage at ground potential.
Otherwise it could drift to a high voltage due to stray static charges or mains transformer leakage and damage anything connected to the mains in your house.

How does any of that happen if current can't flow through the ground conductor?

 

So, if current can't flow from neutral to ground, what purpose does the ground connection serve? High-level diagrams of the generation and distribution system often show the generator also connected to ground, allowing a return path between the consumer and the generator, literally, through the ground, though I've always been skeptical of this, given the resistance of tens of miles of earth. But I digress.

See the paper on the Megger #5.
The earth resistance of an installation can often be measure fairly accurately by separating the neutral and ground at the final installation entrance.
An instrument as the one shown can then used to measure the neutral back to the source where it is earth grounded and then back through the earth.
Generally where the distance is relatively short, the Neutral conductor resistance can be assumed to be zero for this purpose.
A physical ground conductor was often used as a working conductor in early telephone/telegraph where only one conductor was ran the other was the Ground.
Saving on cost.
Max.

 

I don’t have the ability to make a drawing at the moment, so bear with me. On one half-cycle, current flows from the generator, into the panel on the hot wire, through the load, back to the panel on the neutral wire, then back to the generator. If the neutral wire is connected to ground at the panel, why does the current “choose” to flow to the generator and not to ground, the lower impedance path?

Neutral is named neutral because it is the middle (zero-cross) in the 240VAC single-phase waveform that is provided to the panel (aka LOAD Center) on the outside of your house. That panel splits the 240VAC into 120VAC (on either side of neutral). Ground does not connect at the far-end appliance. Instead it is a path-way for FAULT, not a means of providing energy to the appliance.

Normally, HOT and NEUTRAL are INSIDE the device/appliance. GROUND connects to the OUTSIDE/CASE/EXTERIOR of the appliance. The only way HOT or NEUTRAL connect to GROUND at the appliance is if the appliance fails in some way, or some person does something to create a path between HOT/NEUTRAL and GROUND (like sticking fork into toaster).

This then sends power back from the appliance to the load-center via GROUND, going through a BREAKER, which disconnects that circuit- and hopefully saves your life. THAT is the purpose of the ground wire. TO SAVE YOUR LIFE. It is lower-resistance than you which means most of the energy should go through it, rather than you.

 

THAT is the purpose of the ground wire. TO SAVE YOUR LIFE. It is lower-resistance than you which means most of the energy should go through it, rather than you.

Excellent reply.
Newer electrical codes require 4 wires from the breaker box to the pole. Only at the pole is the neutral and ground connected.

 

Excellent reply.
Newer electrical codes require 4 wires from the breaker box to the pole. Only at the pole is the neutral and ground connected.

Only at the pole?
If also no longer in the panel, that is news to me?
In N.A. anyway.
Max.

 

Only at the pole?

I just finished my house this past summer and that was required according to the local building dept. They are currently going by the 2017 code here in the US.

 

How does any of that happen if current can't flow through the ground conductor?

We didn't say no current can flow, only that the normal load current can't flow.

Static charge or leakage current will flow if the neutral voltage is above or below ground to keep the neutral at ground potential.

 

This then sends power back from the appliance to the load-center via GROUND, going through a BREAKER, which disconnects that circuit- and hopefully saves your life. THAT is the purpose of the ground wire. TO SAVE YOUR LIFE. It is lower-resistance than you which means most of the energy should go through it, rather than you.

I've only ever seen hot wires connected to breakers, never grounds (or even neutrals), so I assume that's what you meant. Please correct me if I'm wrong. Regardless, if the ground is there to provide a lower-resistance path for sufficient current to cause the breaker to trip, how is that reconciled with crutschow's claim (in #27) that "the normal load current can't flow" through the ground, so it should be insufficient to trip the breaker?

 

how is that reconciled with crutschow's claim (in #27) that "the normal load current can't flow" through the ground, so it should be insufficient to trip the breaker?

What is your definition of "normal load current"?
Normal load current doesn't flow through the ground wire.
Fault current, on the other hand, due to a short between the appliance hot and safety ground will obviously flow through the ground wire.

I'm beginning to think you are trolling us.

 

I just finished my house this past summer and that was required according to the local building dept. They are currently going by the 2017 code here in the US.

I once worked in a jurisdiction similar, where the local (in panel) ground and neutral were not connected, in this case the ground resistance had to be measured and come up to standard.as per post #22
Max.

 

What is your definition of "normal load current"?
Normal load current doesn't flow through the ground wire.
Fault current, on the other hand, due to a short between the appliance hot and safety ground will obviously flow through the ground wire.

I'm beginning to think you are trolling us.

I'm just trying to understand this stuff, and some of the answers seem contradictory. You're the one who used the term, "normal load current." I assume it could be several amps for something like a heater and still not trip a 15A breaker. For the ground path to protect someone by diverting enough current to trip the breaker, it would have to sink >15A, which doesn't sound like the leakage current you said was all it was capable of sinking.

 

I've only ever seen hot wires connected to breakers, never grounds (or even neutrals), so I assume that's what you meant. Please correct me if I'm wrong. Regardless, if the ground is there to provide a lower-resistance path for sufficient current to cause the breaker to trip, how is that reconciled with crutschow's claim (in #27) that "the normal load current can't flow" through the ground, so it should be insufficient to trip the breaker?

Let me rephrase what I stated- HOT is connect to breaker. The way the breaker is thrown is because the GROUND path in a FAULT condition, poses virtually no resistance (far less than you or the failed device). As such, more current than is normally allowed by design of the devices attached, flows through the circuit, which causes the breaker to trip at the breaker bar in the LOAD CENTER.

Your utility will, for all intents and purposes, provide _any_ amount of current necessary to complete the circuit, if given the chance. As such, it is the load that determines how much current is drawn (by design). A short circuit, which is what GROUND creates in a FAULT condition, removes that restriction, causing the BREAKER rating to be exceeded, and it trips.

Don't really know how it can be made any plainer. GROUND IS FOR _FAULT_ CONDITION. Stop trying to use it in non-FAULT condition.

I worked in the utility in both generation, substation, coal-fired and nuclear. If you persist beyond what I've explained, I will believe you are trolling. Google has endless information about this if you're interested. It is NOT rocket-science.

 

Excellent reply.
Newer electrical codes require 4 wires from the breaker box to the pole. Only at the pole is the neutral and ground connected.

Curious, where/how did you obtain the breaker panel without the ground and neutral terminal bars common,ed up in the panel as they have been up till now?
Max.

 

Can we break your questions down.

a) The earth, is the ultimate sink for all currents.
b) The supply company supply a L and N to you, between which 110V AC is present.
c) Ground is a safety circuit. Not part of the normal current flow.

As we have seen, the two wires L and N , either can be connected to ground,
it does not matter to the source or load,
by convention its the N,
and it does not matter if N is connected to ground at either end or both ends.

Your not sending amps through the earth , you just moving the other wire up /down compared to the earth.

Ok there are various confusions, such as the supply company is probably using three phase, and no N, delta wired,
but that's just a confusion to your original question,

In summary.

L / N is where the voltage is generated across,
Ground is a safety wire,
The N is normally strapped to earth at the consumer premise.

 

Curious, where/how did you obtain the breaker panel without the ground and neutral terminal bars common,ed up in the panel as they have been up till now?

Home Depot. It is a 200amp GE panel. They are made with the neutral insulated from the metal box. There is a thick metal bar that connects from the ground bus to the neutral bus that can be removed for a 4 wire system.

 

It is possible the service neutral was grounded at the meter before the panel, done in some jurisdictions.
Max.

 

You're the one who used the term, "normal load current." I assume it could be several amps for something like a heater and still not trip a 15A breaker.

Okay, sorry if that term is ambiguous.
By "normal load current" I meant the current flowing through the hot and neutral.

For the ground path to protect someone by diverting enough current to trip the breaker, it would have to sink >15A, which doesn't sound like the leakage current you said was all it was capable of sinking.

Where did I say that?
Please read what I say, not what you think I said.

The ground connection (to earth ground) is what maintains the wires at ground potential by sinking any static or leakage current.
It has no relation to with how much current the safety ground wire in the building an carry under fault conditions.
Earth ground and ground wire are two entirely separate things.

 

It is possible the service neutral was grounded at the meter before the panel, done in some jurisdictions.

That's the norm here with any new construction. In my case the ground and neutral are tied together inside the meter panel which is mounted on the pole about 100ft from the house.

 

That's the norm here with any new construction. In my case the ground and neutral are tied together inside the meter panel which is mounted on the pole about 100ft from the house.

I personally don't like that from the technical point of single point grounding and ground potential rise. A near strike can generate a huge potential between non-electrical grounded fixtures at the house like plumbing, unintentional electrical grounding points like TV/Internet cables and the utility electrical ground potential 100ft away generating arc flash-over points.

https://electrical-engineering-portal.com/ground-potential-rise-in-your-home

 

The ground at the breaker panel is also connected by a #4 copper wire to a ufer ground rod encased in the concrete footings and another 8ft ground rod at the pole for the meter panel and pole