How far does the neutral wire run?

Thread Starter

dnharris

Joined Mar 3, 2018
1
I understand the ground wire in the house. Where is the neutral wire actually grounded? (1) at the house, (2) at the pole outside the house, (3) at a distribution point with the electric company, (4) at the electric generation location? (all of these?) The neutral wire extends from the house all the way back to where?
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
In N.A. the neutral is grounded at the supply transformer source and re-referenced to earth ground at the service panel, i.e. the neutral is connected to either a suitable ground such as a metalic water supply pipe, or two 8ft ground rods, at least 6ft apart.
The neutral goes back to the 1phase secondary of the service transformer.
Max.
 

BR-549

Joined Sep 22, 2013
4,928
In the states, the neutral goes back to the line transformer. The neutral is the center tap, of the secondary, of the line transformer.

That center tap is grounded at the power pole. AND at the interior power panel.

Other countries are different.
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
Canada and USA has virtually the same system.
In the UK and IIRC, Australia has a 3 phase star secondary transformer, one phase and the star point , which is the neutral, is grounded at the transformer, and also at the destination panel.
Max.
 

jpanhalt

Joined Jan 18, 2008
11,087
Those answers reflect current practices. In 1983, a commercial building I put up had the neutral and safety ground at the breaker box. Only L1 and L2 came from the distribution transform. That was in Minnesota.
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
Those answers reflect current practices. In 1983, a commercial building I put up had the neutral and safety ground at the breaker box. Only L1 and L2 came from the distribution transform. That was in Minnesota.
How was the neutral obtained?
Was this 1ph?
Max.
 

BobTPH

Joined Jun 5, 2013
9,265
Those answers reflect current practices. In 1983, a commercial building I put up had the neutral and safety ground at the breaker box. Only L1 and L2 came from the distribution transform. That was in Minnesota.
Which is the same as my house is wired. This was done on 2004 in Massachusetts.

Bob
 

Dodgydave

Joined Jun 22, 2012
11,348
In th UK we have Two systems. TNCS, and TNS. Tncs (pme) is where the Earth and Neutral are brought into the domestic property from the street transformer on a Two wire cable,(like a large coax) the earth and neutral are as one, and are then separated at the customer distribution board by a copper bar.

TNS is where the Earth and Neutral are brought in separated from the street Transformer.
 

ebeowulf17

Joined Aug 12, 2014
3,307
Which is the same as my house is wired. This was done on 2004 in Massachusetts.

Bob
Wait! In both of your examples, there's no neutral or ground of any kind from the house to the utility connection? You only have two wires connecting your house to the grid?

So that means all neutral current goes through your ground rod and/or metal water pipes, and that there's no safety backup if that grounding scheme fails?

That sounds crazy to me! I'm not saying it's not true, just that I wouldn't feel comfortable with that system, and I'm surprised it was done in the USA that recently.
 

BobTPH

Joined Jun 5, 2013
9,265
I will check again when I get home, but that is the way I remember it. I was surprised that there were only two connections.

Bob
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
In th UK we have Two systems. TNCS, and TNS. Tncs (pme)
Way back when I did my training in the UK the service provider did not supply a ground, just a phase & neutral.
The neutral was earthed at the transformer star point.
Even if they did supply a GND , you were not allowed to use it and the N and Earth could not come in contact anywhere in the installation, if it did, it did not pass inspection.
You had to supply a decent ground which had to be measured using a megger via the neutral and through ground conduction back to the star point.
I guess things have changed alot since then.:(
Max.
 

ebeowulf17

Joined Aug 12, 2014
3,307
Way back when I did my training in the UK the service provider did not supply a ground, just a phase & neutral.
The neutral was earthed at the transformer star point.
Even if they did supply a GND , you were not allowed to use it and the N and Earth could not come in contact anywhere in the installation, if it did, it did not pass inspection.
You had to supply a decent ground which had to be measured using a megger via the neutral and through ground conduction back to the star point.
I guess things have changed alot since then.:(
Max.
Perhaps this warrants its own separate thread, but I have a question about earth and neutral resistance testing. I've heard numerous people mention needing a megger to test this, but I don't understand why.

In order to be safe and effective, the ground resistance would need to be very low (fractions of an ohm,) right? I thought the main feature of meggers was that they could accurately measure much higher resistances than typical multimeters. Are they also much better at measuring extremely low resistance values?
 

SamR

Joined Mar 19, 2019
5,078
If done properly the ground is megged here in the US and if failed additional grounding provided until passing. Where I live (there isn't a traffic light in my county) the so-called building inspector has no clue about the NEC and most local residential electricians are clueless about megging. There are L1, L2, and center tapped Neutral wires from the transformer to the residential panel. The panel neutral and ground are bonded and grounded to either a single 8' copper (usually clad) ground rod (preferred) or a metal incoming pipe as close to panel as possible. The feed transformers center tap/neutral is also grounded at the pole or transformer pad.
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
Perhaps this warrants its own separate thread, but I have a question about earth and neutral resistance testing. I've heard numerous people mention needing a megger to test this, but I don't understand why.

In order to be safe and effective, the ground resistance would need to be very low (fractions of an ohm,) right? I thought the main feature of meggers was that they could accurately measure much higher resistances than typical multimeters. Are they also much better at measuring extremely low resistance values?
There are/were two basic types of Megger, this was in the days of the hand-crank versions, one was a high voltage type for measuring insulation resistance, switchable and imposed such as 500v or 1kv.
The ground resistance version measure extremely low resistances, and was used to measure the loop from the neutral to the earth star point and back to the panel via earth GND.
Quote:
There is not one standard ground resistance threshold that is recognized by all agencies. However, the NFPA and IEEE have recommended a ground resistance value of 5.0 ohms or less. The NEC has stated to “Make sure that system impedance to ground is less than 25 ohms specified in NEC 250.56.

Max.
 

mvas

Joined Jun 19, 2017
539
I understand the ground wire in the house. Where is the neutral wire actually grounded? (1) at the house, (2) at the pole outside the house, (3) at a distribution point with the electric company, (4) at the electric generation location? (all of these?) The neutral wire extends from the house all the way back to where?
1) At the house ?
Yes, the Residential Neutral wire is usually bonded to ground inside the Main Panel.

2) At the pole outside the house ?
Yes, the Residential Neutral wire is usually bonded to ground at the center tap of transformer on the pole

4) At a distribution point with the electric company ?
Yes, at the Secondary Substation
Both the Consumer Neutral wire & the Transmission Grid Neutral wire are both connected to a Ground Array

(4) At the electric generation location?
Yes, at the Generation Station
The Transmission Grid Neutral wire is connected to a Ground Array

NOTE:
The Residential Neutral wire carries the unbalanced AC amps.
The Transmission Grid Neutral wire does not carry any AC Power, therefore it is really just a Ground Wire for Static / Lightning protection.
The High Voltage Transmission Lines, in the USA, uses a 3 Wire Delta design - the overhead Ground wire(s) are called "Neutrals".

Generation & Distribution ...
https://wellread.me/480v-3-phase-wi...o-wire-3-phase-throughout-480v-wiring-diagram

In the above diagram, it does not show any direct bond between the Consumer Neutral and the Transmission Neutral, at the substations.
Recently, it was decided that that all "Neutral" Wires would be bonded together, to share every ground point - system wide.
 

MaxHeadRoom

Joined Jul 18, 2013
28,825
Yes, single phase. Neutral and ground were both by ground rod. It was at an airport and even though 3-phase was available at the other end of the field, running the line that far was prohibitive.
So where did the N originate from?
Was this a grounded phase at the supply?
Max.
 
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