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Normally in our 230V power outlet, the voltages are as given below.

  • Neutral to Earth - Less than 2V

  • Neutral to Phase - 200V to 230V

  • Earth to Phase - 200V to 230V

But nowadays, after around 10 am, until the evening, these voltages change as below with some variations as the day progresses.

  • Neutral to Earth - 77V

  • Neutral to Phase - 228V

  • Earth to Phase - 282V

After the inspection by the power distributor in our neighboring firm, it was found that there is a short between the phase line to the body of an electrical panel when the power switch of a fan is turned on. But they have not rectified the problem yet. So our electrician shorted the neutral to earth (ground) at our power entry point. Now the neutral to earth voltage is close to zero.

But is this a good solution?

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  • \$\begingroup\$ Why should anything be wrong? \$\endgroup\$
    – Andy aka
    Mar 26, 2015 at 9:19
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    \$\begingroup\$ @Andyaka: my guess would be him wondering about 77+228 != 282 ... \$\endgroup\$
    – PlasmaHH
    Mar 26, 2015 at 9:22
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    \$\begingroup\$ Or that Neutral to Earth should be 0V rather than 77V. The neutral isn't connected to earth properly \$\endgroup\$
    – Dan D.
    Mar 26, 2015 at 9:24
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    \$\begingroup\$ Sounds like a bad connection between neutral and the earthing point. Might be corrosion in a wire. Could just need a screw tightened in the wiring. The hard part is finding where... \$\endgroup\$
    – Spoon
    Mar 26, 2015 at 12:50
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    \$\begingroup\$ Where are you on this planet, and what sort of electricity distribution earthing system (TT, TN-C, TN-C-S, TN-S, or IT) does your utility use? \$\endgroup\$ Aug 8, 2018 at 0:11

4 Answers 4

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As the comments already said, this is most likely due to a break in the neutral:

A floating cable next to the phase wire collects some voltage due to capacitive/inductive coupling. As your measurement device also plays a role, you usually will not measure 77V, 151V and 228V (=151V+77V) between the three wires. However, 77V is a typical voltage measured in this case.

Finally, neutral is broken, because you measure the expected voltage between earth and phase, and neutral gives strange results. If you connect any load to the circuit, you will see that neutral will be at 228V to earth an 0V to phase.

Once I had the same problem. Finally, there was a single luster terminal where all neutrals of a room (five) were connected to. One of them was pushed in too far, the part inside the terminal was covered by insulation. The screw bit into the insulation, and it was working for 20 years. From one day to the other, the connection became loose. This could have ended up in a disaster, but there was not even a sign of heat at the terminal.

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to add to comments already said;

Hi Adbul, a friendly note, please have any live electrical works done by professional electrician. Electrical power is dangerous and it is critical that your house PE protective earthing system is in correct working order for both personal and asset safety.

The shorting of neutral with earth conductor at main incomer panel / fuse box is acceptable if your house main power is provided by the utility as a two wire system ( Active and other is neutral). In this situation you should have an earth bond electrode buried in the ground closer to main incomer panel. But again this connection to electrode has to be in good working order, otherwise earth connection would become active if neutral wire from utility is broken.

If you have more than two wire coming from utility then shorting of earth connection with neutral is not acceptable.(Active, neutral and PE are provided by utility. In this instance neutral and earth connections are bonded already at supply transformer)

The short circuit between phase line to body of electrical appliance could be due to fault within fan motor winding. There could be a phase to ground insulation failure within the Fan Motor, which is a common type of failure due to aging. If this is the case then this fan need to be disconnected and replaced.

If your house does not have a RCD installed, then it is recommended to have one installed for personal safety.

Hope this helps.

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  • \$\begingroup\$ +1 You are correct, he nominal place for neutral to be bonded to protective earth is after any transformer. However having the protective earth connected to a local actual ground is a sound practice that protects you in the event that the supply earth is disconnected. As you say in most cases when you are provided with a supply earth and neutral it is the utilities role to connect them and no yours. \$\endgroup\$
    – KalleMP
    May 18, 2018 at 5:59
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Instead of 2 faults there are now 3.

Best to get them all cleared.

If you have a grounded metal water main or reliable earthing point you could check to see if your whole service is not 77 volts above the true ground. If this is the case I would keep phoning service number every hour to have the problem repaired immediately. Avoid uninsulated equipment as much as possible while waiting. Unplug physical telephone line fax/modem/answering machines if still using them and cable TV/internet incomer to avoid damage from uncontrolled ground loops. Use gloves on coax connector.

  1. Neighbour has damaged equipment.
  2. There is weak grounding on your (shared) earth circuit letting it float or there is a resistive neutral letting it droop.
  3. Bonding the neutral and earth at your power entry may cause all this (possibly large) leakage current to flow into and out of your incoming cabling through the connection while the neighbour is waiting to get their equipment serviced.

I would hurry them along and then have your local ground and earth and neutral conductors inspected after removing the neutral ground bond. It is not a good idea to leave the situation like this. Your local RCD/earth-leakage-detector should still be protecting you if the bonding was done on the supply side.

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Your "electrican" is a dangerous cowboy AND your electricity supplier is feeding you misinformation.

Your results tell me that the real problem is a bad neutral in the electricity suppliers wiring, other faults may have contributed but that is the primary problem and it needs to be rectified ASAP.

By connecting the neutral to the earth you have effectively turned the earth conductor into a combined neutral and earth conductor. This indeed solves the immediate problem but it raises two problems of it's own.

  1. The earth conductor was designed only to carry brief fault currents, it may be significantly undersized for carrying continuous operating currents.
  2. Combined neutral and earth conductors require specicial care to minimise the risk of a break since a break in a combined neutral and earth conductor can be very dangerous. A conductor that was intended only to be an earth conductor is unlikely to have been installed to such standards.
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