Large Neutral-ground Voltage.

[Crossy]

People.

I got the following PM from another member. I'm at a loss as to exactly what to advise to fix this issue. There is certainly a problem, and the massive N-E voltage suggests that MEN is not implemented (so a ground-neutral link would be ill-advised).

Bright ideas anyone??

My house is 3-phase connected to the grid and I have tried to balance the load equally over the phase as good as possible.

The phase to neutral voltages are 233, 228 and 225 volts, a slight difference but that doesn't bother me. I live a few hundred meters from the transformer but there are a lot of 1-phase connected houses on the same run, so it is probably there the unbalance comes from.

But my neutral to ground voltage is 40V which right now seems to cause havoc for one of my computers, it won't work when connected to a grounded outlet.

Anyway, I have also checked the neutral to ground voltage at the incoming point (the meter at the pole) with the house completely disconnected from the grid and it is the same 40V diff, so the problem is not on my side. I have never seen such high neutral to ground voltages before so I am a bit worried now about jumpering neutral and ground in the distribution panel, something I had planned to do.

I'm about to go to the power company and complain but would first like to know if voltage difference like this are common?

Any thoughts of where they can come from?

[technocracy]

I had exactly the same problem - you might remember me posting about getting zaps off the neutral.

For me the problem was resolved by getting my own transformer since the amps on the shared village transformer weren't enough for our needs.

I quizzed them about the voltage on the neutral and they just said it's normal!!

Edited November 3, 2008 by technocracy

[elkangorito]

People.

I got the following PM from another member. I'm at a loss as to exactly what to advise to fix this issue. There is certainly a problem, and the massive N-E voltage suggests that MEN is not implemented (so a ground-neutral link would be ill-advised).

Bright ideas anyone??

My house is 3-phase connected to the grid and I have tried to balance the load equally over the phase as good as possible.

The phase to neutral voltages are 233, 228 and 225 volts, a slight difference but that doesn't bother me. I live a few hundred meters from the transformer but there are a lot of 1-phase connected houses on the same run, so it is probably there the unbalance comes from.

But my neutral to ground voltage is 40V which right now seems to cause havoc for one of my computers, it won't work when connected to a grounded outlet.

Anyway, I have also checked the neutral to ground voltage at the incoming point (the meter at the pole) with the house completely disconnected from the grid and it is the same 40V diff, so the problem is not on my side. I have never seen such high neutral to ground voltages before so I am a bit worried now about jumpering neutral and ground in the distribution panel, something I had planned to do.

I'm about to go to the power company and complain but would first like to know if voltage difference like this are common?

Any thoughts of where they can come from?

It could be a high impedance as a result of a poor earthing electrode.

It could also be that an active conductor (some distance from the main earth electrode) is touching an earth. I witnessed this very situation not long ago.

The problem turned out to be "overgrowth" of vegetation touching an active conductor (it was a 3 phase supply). Since the M.E.N. System was poorly earthed (not often enough), the Earth Fault Loop Impedance was too high to allow any OCPD (Overcurrent Protective Device) to trip.

The solution was to disconnect the M.E.N. link & install/check the following:

1] install a 100mA RCD/MCB as the Main Switch in the distribution board (fire protection) & to also install, as required, 30mA RCD/MCB's as required by individual downstream circuits.

2] ensure that the Main Earth Electrode is adequate (minimum buried depth - 1.8 metres) & "copper clad".

3] ensure that the connection to the Main Earth Electrode is not damaged.

4] ensure that the minimum size of the Main Earth conductor (from the distribution board to the Main Earth Electrode) is a minimum of 4mm² copper cable.

5] ensure that all connections to the earth & neutral bars within the distribution board, are not faulty (loose or over-tightened).

Unfortunately, I was not able to check the Earth Fault Loop Impedance since I do not have the appropriate equipment.

Also, a partial insulation failure within the installation may also present the problem of a neutral to earth voltage if the Main Earth has a high impedance. Thus an insulation resistance test is also advised for the complete installation.

Edited November 3, 2008 by elkangorito

[tjo o tjim]

Sure sounds like an ungrounded system. The American solution would be to provide an isolation transformer where you can provide your own earth connection, but at that point you might as well get a dedicated service transformer. If you aren't concerned about safety, you could just provide an isolating transformer for the computer, but you will be getting shocked on everything else.

If you do jumper earth and neutral at your consumer unit you could get up to 600A or so flowing through, which will quickly cause significant problems and could cause a fire.

[dotcom]

In any case consult MEA or PEA for a fix.

[djc45]

People.

I got the following PM from another member. I'm at a loss as to exactly what to advise to fix this issue. There is certainly a problem, and the massive N-E voltage suggests that MEN is not implemented (so a ground-neutral link would be ill-advised).

Bright ideas anyone??

My house is 3-phase connected to the grid and I have tried to balance the load equally over the phase as good as possible.

The phase to neutral voltages are 233, 228 and 225 volts, a slight difference but that doesn't bother me. I live a few hundred meters from the transformer but there are a lot of 1-phase connected houses on the same run, so it is probably there the unbalance comes from.

But my neutral to ground voltage is 40V which right now seems to cause havoc for one of my computers, it won't work when connected to a grounded outlet.

Anyway, I have also checked the neutral to ground voltage at the incoming point (the meter at the pole) with the house completely disconnected from the grid and it is the same 40V diff, so the problem is not on my side. I have never seen such high neutral to ground voltages before so I am a bit worried now about jumpering neutral and ground in the distribution panel, something I had planned to do.

I'm about to go to the power company and complain but would first like to know if voltage difference like this are common?

Any thoughts of where they can come from?

I have asked the way the wiring works in Thailand and have it explained by highly educated electrical technician working in the uk the following

In Thailand its is not the same as the uk it would appear from the information I gave him about the electrical supply to my house in Issarn.

From the supply substation they only send a live feed and the second feed that you see over head is NOT a neutral supply feed but an earth a neutral is not needed to power up anything,

You can test this in the uk by wiring a light bulb up with the live wire to a live in a 3 pin plug and the neutral to the earth terminal in the plug and the bulb will light

The way it has been explained to me is that in the uk you would get a live feed and a neutral feed from the substation and the earth would be taken from a local source such as an incoming lead pipe or copper pipe or earth spike

Here in Thailand it would seem that the (neutral) is in fact a cable that just goes into the earth this is connected to the neutral terminal giving you the false idea that you have a neutral feed

If you then try to introduce an earth feed by way of a earth spike you could in fact cause more problems as any short to earth through the earth feed could return via the neutral wire

Most electric showers if not all that are sold in Thailand have a built in ELB with an earth wire connected to an earth spike un like the electric showers you see in the uk this is so that the power is switched of at the shower and the live cannot continue to the earth spike and back to the false neutral feed

If you look close at your incoming over head wires that supplies the incoming electricity you can see that the neutral wire when traced back to the joint has an UN insinuated wire running down the concrete pole into a conduit that goes into the earth

I hope this will she some light on the subject