High neutral voltage

It seems that quality of earthing is very bad, ideally resistance must be 0 ohm,

you should not run your comp at this connection it can damage your hard-disk.

<...it can damage your hard-disk...>

There's more to it than that. It can shorten one's life!

HI,

It shows there is neutral disconnection in your building. Could it be at junction box / switch box / one stage prior to switch box.

It's advisable to rectify the problem before plugging your computers, as electronic device are sensitive to neutral & earth voltage

Regards,

Mahesh.D

can u tell why my computer runs if neutral disconnection in the building?

Given that the building is not earthed, as stated below, then for the computer to run then there would need to be two simultaneous faults:

• a connection between neutral and earth elsewhere in the building (has another tenant connected a neutral to a water pipe? It is to be hoped it can carry all the current that the open neutral link would normally pass!!)
• a connection between neutral and earth in the computer in question, indicating IT REQUIRES INVESTIGATION/REPAIR/REPLACEMENT BEFORE IT IS ENERGISED AGAIN AND BEFORE SOMEONE GETS AN ELECTRIC SHOCK.

It would seem that there is a poor connection between neutral and earth/ground at some point on the local distribution system. If the problem can be shown to lie upstream of the distribution company's connection to this building, then their specialists need to be advised to attend, investigate and rectify the problem, as other users in the locality will be experiencing the same issue. It could, in the limit, cause safety issues either in this building or elsewhere.

Check the inlet rating of the device to be connected. Supply voltage varies by several % over the course of a day and the inlet will have a tolerance on the voltages to be accepted. Follow the manufacturer's recommendations in the user manual, and make a judgement based upon that information. 243V between live and neutral is within normal expectations for the UK.

Many devices these days have the ability to accept a range of voltages and frequencies that overcome national boundaries and the differences in their distribution systems.

In the UK the tolerance is +10% or -6% of the suppliers voltage, nominally 230V.

You should check the earth loop impedance to the source of supply.

If this is not within tolerance then there is a problem with the supply.

where are you measuring the voltage? what sort of an earthing system / arrangement do you have? are others sharing the supply? are you in a house or a flat?

I am in a flat.

there are many rooms in the flat. and each room has separate meter for measuring the power used by individual room.The power has been distributed in each room from one point.

I am measuring the voltage between the pins of power outlet where i connect my computer.Like between ground and neutral pin, phase and neutral pin

there is no earthing in my building.I have taken earth separately for my computer from outside. I have connected the ground pin of power outlet(where i connect my computer) with a wire that is coming from electricity pole.If i dont connect ground pin of power outlet with the wire coming from electricity pole and touch my computer then it shocks me.So i have connected the ground pin of power outlet for grounding purpose.But now i am not able to know whether fault is in my earthing system or in the neutral system,

Can u tell me what are the other ways for good earthing?Because i live on rent and i dont want there to do earthing by digging the earth.I asked with the owner to connect the ground wire with the water pipe. he refused for it.

Now can i connect my ground wire with the concrete of roof.

wating for reply

<there is no earthing in my building>

It is worthy of correction at the earliest opportunity, on safety grounds. The building owner might be liable if a tenant were to be inadvertently electrocuted, and this is sufficient grounds for the owner to sort out the problem by working with with the local supply company to create an effective earth connection for the whole building.

<I have connected the ground pin of power outlet(where i connect my computer) with a wire that is coming from electricity pole.>

Make sure it is the correct wire.....

<But now i am not able to know whether fault is in my earthing system or in the neutral system>

It depends on what the perceived fault is. A neutral of several tens of volts would indicate an imbalance in the power supplied on each phase outside the building (not usually much of a problem apart from conductor sizing in the distribution system) and possibly a poor connection, or no connection at all, between neutral and the star point of the local distribution transformer. It may be that the local installation is so haphazard that none is provided, in which case a local earth would give a measure of protection. It wouldn't have any effect on the 243V measured between live and neutral.

<I asked with the owner to connect the ground wire with the water pipe. he refused for it.>

What is unclear is whether the metallic parts of the building's water pipes are sufficiently contiguous with the local soil structure to assure a good earth connection. If not, then connecting the case of this computer to the water supply system would still give shocks, except that the problem is now being observed in other flats where there are water pipes as well as on the case of this particular computer. In this case the building owner would be correct in protecting other tenants by refusing consent for this connection to be made. The computer would be raising the voltage of the water pipes to a point where other occupants would receive a shock.

An electric shock usually indicates an appliance is faulty and needs investigation/repair/replacement.

A 30mA RCCD placed in the lead from the wall outlet to the computer would protect the user against the effects of shock, though it may be inconvenient for the if the power goes off at the RCCD halfway through a CR4 posting!

<Now can i connect my ground wire with the concrete of roof.>

Concrete is quite a good insulator when dry, so the reasons for wanting to do this are presently abstruse.

http://en.wikipedia.org/wiki/Earthing_system

This problem in my opinion is a little more than just a simple grounding issue. As raised in an earlier reply, it would depend on the wiring/supply authority standards used. Here in Australia (and similarly in most places) the neutral is bonded to earth at the fuse/circuit breaker main switch board, so you should have very little potential (voltage) between earth and neutral. If you disconnect the ground then the potential of the metal casing of the pc will be able to 'float' to voltage above ground, and therefor you get a shock. Luckily you have not got electrocuted, this is a serious safety issue.

Electrical induction is a very little known pheneomenen. Look to see what is connected to the electrical system and see if this cures the 'shocks'. EARTH ALL EXTRANEOUS METALWORK' Then your prorection system will work.

i am also from india , i would like to know in which city you are living? I do not know how can be no earthing for the building.It looks apparently there is floating neutral,due to which there is voltage between earth and the neutral.Please inform your electricity service provider about the desparity.Can you inform us whether your flat is getting single phase supply or three phase supply?

This gentleman has a very serious safety problem and It is difficult for others that may not know the standards of your country to comment and/or advise.

Since you are a native of the country I urge you and him to get together and see if you can solve the problem for him. I suspect there is much that is unsaid about this situation.

Meters in every room may indicate that the owner is re-selling electricity (frowned on in the US) and has wired the building himself in violation of codes.

To complain may cause eviction, to not complain may result in death by electrocution.

I am living in Delhi,New kondli

here is single phase supply.

Single or three phase supply is irrelevant. Earthing applies to all installations. Contact your local supply authority. Phase voltage to earth should be the same (or almost) as phase to neutral.

Concrete does not conduct electricity. Connect a ground wire to the ground!

Your neutral is not referenced to ground. If you have truly connected to the ground of the supply pole you may be experiencing effective voltage rise on your neutral caused by the volt drop along the supply line to your flat. But you need a functional earth for your computer, its switched-mode supply dumps harmonic current to earth as part of its function and that may be the cause of the shocks you are experiencing - but in order to get a shock you need to complete a circuit, so what else were you touching? It must be the external earth that you are introducing to your computer (and its case) and something else. The concept of equipotential bonding means that every metallic part which can be touched and is likely to introduce a potential should be connected by (a reasonable thickness) protective conductor. You will have to investigate your flat measuring between water pipes, between water pipes and neutral etc.

(If you connected the neutral to the earth at the meter that could cause all sorts of problems, only some of which I can imagine).

An isolation transformer supplying only your computer which has its output neutral connected to a point you define as earth to your reference earth may solve this problem. (You will get magnetic coupling so check with your meter that your output neutral is about the same potential as your supply neutral, it makes life simpler later). It's difficult to say more at this distance. What are your protective measures? RCD / MCB / fuses

Genarally the System Earth should be Isolated from all other earth. You provide separte earth for Computer.Any gardening area 2feet earthing adequate for testing.Try your self.Your proublem will be solved.Dont take Electricity board earth.

There should not be a voltage on the neutral. (N=0v).

Contact your supplier of electricity.