Voltage Between Earth and Neutral 220V

What are your phase to phase readings..? What do you expect to see in each of these readings?

phase to phase in 384.. ry, yb, br all same... but exact resaon i cannot find why there is 380 V between earth and phase for r and y phase. i checked with clamp ammeter 0.4 A in neutral and .34 A in earth.... and when i switch of all the machine connected to the distribution board and short the neutral and ground and remove the short phase to neutral is 20 V for all the r, y, b.

another thing my Distribution panel is connected to a distribution transformer. the secondary side has 3 phase and neutral as usual. the body of transformer is grounded. there is no problem with the phase to neutral. its 220 with all the phase and no unbalance is found.

earth and neutral need to be at same potential if the short earth and neutral will i be able to find a solution with compromising the safety factor.

i check teh continuity of the earth from panel to pit , pit to distribution panel board it 0.8 ohms.

phase to phase in 384.. ry, yb, br all same... but exact resaon i cannot find why there is 380 V between earth and phase for r and y phase. i checked with clamp ammeter 0.4 A in neutral and .34 A in earth.... and when i switch of all the machine connected to the distribution board and short the neutral and ground and remove the short phase to neutral is 20 V for all the r, y, b.

another thing my Distribution panel is connected to a distribution transformer. the secondary side has 3 phase and neutral as usual. the body of transformer is grounded. there is no problem with the phase to neutral. its 220 with all the phase and no unbalance is found.

earth and neutral need to be at same potential if the short earth and neutral will i be able to find a solution with compromising the safety factor.

If possible, disconnect all loads (open breakers). It appears there is a fault between the blue phase and earth somewhere. If the problem disappears with all breakers open, close them one at a time until the problem returns.

"there is no continuity between the neutral and earth."

Get your terminology correct or nobody will understand what you are doing. You do not have a neutral. By definition a neutral is bonded to earth. With proper bonding the bonding connection between earth and neutral needs to only sustain a fault current long enough for automatic disconnects (fuses and circuit breakers) to interrupt the fault condition. You might have a return and how this node interacts with your three phases is the key to your dilemma.

You must identify how the power transformer wiring, particularly the secondary wiring.

the volatage between earth and neutral is 220 V. there is no continuity between the neutral and earth.

Down here that would be a big red flag as the earth and neutral need to be solidly connected (both at same 0V potential) as we run a MEN (multiple earth neutral) earthing system.

I don't know what country or earthing system you are running but if it is similar you need to check your earth neutral bond in your switchboard.

Please provide a clearly labelled schematic of the voltage source and load, and the circuitry between them.

One of the possibilities is a loose or missing neutral-to-earth link at the main distribution transformer.

Have the local utility supplier check this out and report before proceeding.

This is a safety issue. The system should remain isolated until the above report is to hand.

thank you for your valuable comment,

you are right the neutral ground bonding has been intentionally cut by whom and why have got no idea. but the earthing for the equipments is good.

our system not make use of the neutral so the person who or organization who made the connections left out neutral wire and instead used this wire as body ground which is connected to the earth of the factory. so personal safety is not compromised. but still the neutral bar which is not grounded have connections to the light and air conditions due to which a residual voltage (or floating neutral) is found.

what i paln is to shut down the particular transformer and make a separate earth pit and connect the neutral to this earth pit.

and would like your suggestions regarding this solution or another most feasible solution.

It’s possible that the earth fault on the blue phase could not be found or repaired easily, so essentially converting the system to ungrounded operation allows continued operation.

That is, until a second ground fault occurs on a different phase. This now becomes a phase to phase fault, and will activate your protection.

Adding a 10 ohm ~500 watt resistor between neutral and ground converts your system to high resistance grounding, then you can use a loop type galvanometer to trace the location of your ground fault, if it comes to that.

If the neutral link is missing then the installation becomes an IT one, in which case improving the local earth will achieve diddly squat.

A discussion with the local distribution network operator is overdue, on safety grounds.

Who is to blame is irrelevant.

Another thing to try is to connect a low-wattage filament lamp between neutral and earth upstream of all residual current devices briefly, and measure again.

Remove the lamp immediately after measuring.

Quaiser,

Two important points you have mentioned:

First-- you "prepared a new earth pit then the voltage between earth and neutral was 3 volt and after 2 days again there is 220 v"

Second-- you measured 0.34A on the earth connection.

Another person suggested that the continuous current into the earth pit has dried it out and raised its resistance enough so the voltage has risen as you noted. R=E/I, so your pit resistance has risen to 220/0.34 or about 660 ohms.

Often an ungrounded (non-earthed) system is desired, if installed with earth detectors in place. Then the first fault to earth will be shown by the detector, giving you time to find it and repair it without a sudden and unplanned shutdown of your process. You don't mention having any earth detectors, so I assume you have a fault in the earth conductor.

Almost all power systems in plants will have capacitive and inductive coupling between the conductors and neutral. This can be anywhere from a few to hundreds of volts. You appear to have this along with the resultant neutral-earth voltage this causes because of an open earth connection.

As others have said, find the open earth connection and also check to find why you have 0.34 A on the earth conductor (it should be significantly less). This current is probably due to a high-resistance fault somewhere in your wiring or equipment.

--JMM

Hi, the problem is two parts. One is neutral to earth is more. Another B phase to neutral is very less.

The reason may be Bphase is getting connected to neutral with a very low resistance and neutral is not earthed solidly.

I hope your system is load side star and neutral solidly earthed.

If you are sure that the reasons mentioned above are not true, please check your transformer. Use multimeter to check continuity and IR tester for insulation values.

Like to hear the feedback from you

Ayyagari Srinivas

Why is blue a phase?

Most wiring schemes use blue as neutral and have brown/ red or grey/ black as phases.

Please check your local wiring regs. Sounds like someone mis-wired this. Error may not show up until new protection is added.

Heritage installation: before the latest BS7671 changes, red/yellow/blue were phases and black neutral. Now, brown/grey/black are phases with blue neutral. Lots of potential (pun intended) to get it wrong now!

Those changes were back in 2006.

I suppose someone who has qualified since then may have been working on another part of the system and crossed the blues.

That's why qualification as an Electrician takes several years' training and experience.

That possibility doesn't explain why there is no continuity between neutral and earth, nor why the testing Electrician ignored it before its first energising nor why subsequent individuals testing it have also.

The original poster has not given details of the location of the installation. Were it to be in a hospital, for example, where IT installations are commonplace, one wouldn't expect continuity between neutral and earth except in the case of a first fault; generally a first fault will not stop the installation operating, which is vital to save lives if it were driving life support systems.

Yes, we once again do not have sufficient information from the OP to provide clear guidance. One of the pivotal missing pieces of information is what region is this installation. We could then suggest which code the installation should be following.

From Wikipedia, here the National Electrical Code defines a neutral as this:

• Neutral wire is the return conductor of a circuit; in building wiring systems, the neutral wire is connected to earth ground at only one point. North American standards state that the neutral is neither switched nor fused except in very narrowly defined circumstances. The neutral is connected to the center tap of the power company transformer of a split-phase system, or the center of the wye connection of a polyphase power system.

The United States electrical codes require that the neutral be connected to earth at the “service panel” only and at no other point within the building wiring system. Formally, the neutral is called the “grounded conductor”; as of the 2008 NEC, the terms “neutral conductor” and “neutral point” have been defined in the Code to conform to what had been common usage.[1]
If a conductor is not connected to earth ground then it is not a neutral! (The relevant NEC code is available to all after registering. The Wikipedia text was copied.)

Indeed.

British practice allows for variations.

I don't know what the standard is now, but in the 1990's when I (in the USA) was engineering the electrical for a beverage can warmer being shipped to Australia, the required color code was Red/White/Blue for phases and Black for neutral. My panel builder had a challenge to do things that way.

I don't recall that we were told what country this installation is in.

--JMM

...a stab in the dark...maybe a fault (I guess broken neutral) on a totally separate system using 'earth' as a (temporary return) - (or even intermittent phase/earth fault) thus causing a 'high' earth voltage at the place you test it....

...it could be a +220v earth to 0v neutral reading...

thanks for all the comment pwslack, jmueller, rwilliams and rest people thanks. this community solves most of the problem beside getting extra solutions and reason that may have caused that..

coming to the problem almost the problem is solved.. there are three drive 250 KW the cables shields for the output side is the reason i could find.. the shield is exposed and today it came in contact with the conductor resulting in the drainage of current through shield to the ground and causing OC fault. i think i need to reinstate the shield and insulating medium for the cable by electrical putty, rubber tapes then a copper braid above to connect to broken shields and again insulating with a rubber tape and pvc tape and at the end with the heat shrink tube.

its tedious so i would update as soon as possible. thank you

If you share the transformer with a neighbor, the problem could be there. Or, the transformer bonding has failed. Talk to your electric utility.