Floating Neutral in 3-Phase Apartment: Voltage Fluctuations and Burnt Neutral Wire?

Dear all, please help me.
I read on the forum but did not find the answer to my question.

Something happened to the installation while I was away from the apartment for a month. After returning, it turned out that the TV was broken and the bulbs in the lamps were blinking, especially in the evening. I don`t want my other devices damaged.

According to the information I obtained on the forum, I have a problem with a floating or hot zero at home. I checked the fuses with a meter. One may receive 190V and the other may produce 270V.

It is a relatively new (5-year-old) apartment. 3 phase power supply, grounding, etc. etc.

And now my question.

If I turn off all fuses, there is 230V at the entrance to the apartment on all phases. When I turn on the fuses one by one, the voltage changes as I wrote above.

Should I look for a burnt neutral wire in the apartment or is it possible that it is somewhere before the fuses, despite my measurements that if I turn off the fuses, the voltage before them is correct.

How to find a damaged cable? Should I disconnect all neutral wires in the switchboard and check them one by one with a meter?

The way you describe it shows that you have very little understanding of electrical installations. So why don`t you use an electrician? Do you think you can handle it? On what basis?

ziller wrote:

Should I disconnect all neutral wires in the switchboard and check them one by one with a meter?

It`s hard to imagine a more idiotic idea.

I have a vague idea - as you wrote.
But I want to know what and how. I like to know what my problem is.

Of course the electrician - the second one - will come today.

There was one yesterday, he looked at it, looked in the fuse box and said it was OK, but nothing had changed. And there was still beer pouring from him a mile away.

That`s why I`m pursuing the topic.

I`m asking because if there is a 100% problem in the apartment, it will have to be repaired by an electrician whom I "hire" myself. However, if there is a possibility that the problem with the zero is in front of the apartment, there will be a different "procedure" for calling an electrician.

I just don`t want to waste time and if this may be a problem before the apartment, immediately intervene in the community or energy.

That`s why I`m asking for advice.
Can it be in front of the apartment despite my measurements, and if only in the apartment, how to look for a damaged cable?

First, in a VOLTAGE-FREE condition, visually check the switchboard for any soot, then check all screw connections. It may happen that the clamp breaks or the cable is not inserted properly. If it doesn`t help, call an electrician.

Nothing is sooty, everything is tightened up.

Hello.

ziller wrote:

If I turn off all fuses, there is 230V at the entrance to the apartment on all phases. When I turn on the fuses one by one, the voltage changes as I wrote above.

Exactly. Between the phases and the neutral/zero terminal... where? You need to find another terminal or a place where there is no voltage (so-called zero), then there is a break in this section. Of course, we check all the time with these fuses turned off so as not to damage other receiving devices.
Still, it`s not much work for an electrician to find out the cause.
The grounding that my friend mentioned can also be misleading, so it needs to be unplugged during this check.
If your friend doesn`t feel up to it - you need a normal electrician, not a "kilometer-long" one.
With meters, not just a light bulb and a neon lamp.

Buddy, you won`t find the location of the damage with an ordinary multimeter. A fault loop impedance meter is needed. And a sober electrician.

Thank you all very much for your help.
An electrician (tested, experienced and sober) is scheduled to visit me this afternoon.

The first, tipsy one, was sent to me by the "Housing Community".
I didn`t choose - I just got :-)

Today someone completely different will come. I hope he finds the problem.

-----------

But I`m just sitting here thinking like a "guy" and please correct me if I`m wrong.

If I turned off the fuses, disconnected all the neutral wires in the switchboard and took the "light bulb with battery" and checked all the neutral wires one by one, I should find the damaged one.

Theoretically yes, but...
You still need to know how and where to look.
Because there is no main "neutral" wire, not just some one from the circuit.

If "someone else" is supposed to come, wait until he comes. And for now, forget about "peasant common sense" considerations.

If I were a man of common sense, I would take a 100W bulb and WLZ would happen.
PS: And how much does the short-circuit loop measurement show behind the pre-meter protection?

Hello.

opamp wrote:

PS: And how much does the short-circuit loop measurement show behind the pre-meter protection?

And who was supposed to do it? The one sent by the Community?

So far, it has turned out that the neutral wire that goes from the switchboard with fuses in the apartment to the meter, which is 4 floors below, is interrupted somewhere. A cable expert is coming tomorrow and he is to use some device to check where the break is and either repair it or somehow push an additional neutral wire through the conduit. I don`t know if it will work. We`ll see. For tonight, zero is bridged with yellow-green and everything works as it should. But only until tomorrow so that the stuffing doesn`t spoil in the freezer :-)

Near the counter on the strip, checking with an ohmmeter between zero and yellow-green gave a result of around 1 ohm. In the apartment, at the other end of the same cables, the measurement gave crazy values around minus 150 ohms (resistance can be negative??? ) Maybe I looked at it wrong

Now my friend writes -

Quote:

So far, it has turned out that the neutral wire that goes from the switchboard with fuses in the apartment to the meter, which is 4 floors below, is broken somewhere.

Earlier there was such a statement -

Quote:

If I turn off all fuses, there is 230V at the entrance to the apartment on all phases.

One contradicts the other!

bronek22 wrote:

They should pay you to fix the TV.

Dealing with the community? I don`t have time for this. Fortunately, my insurance company will pay me for the repair because my policy also covers overvoltages.

elpapiotr wrote:

One contradicts the other!

As I wrote at the beginning, I have a vague idea, but it seems (in my opinion) that this main neutral wire is not only completely broken, but seriously damaged, and after 5 years it has fallen apart to such an extent that it is causing problems. Maybe somewhere along the way it is drilled, broken, etc.
Some magician is supposed to come today to check the wires and find where the break is.

The fact is that omitting this wire and temporarily passing neutral through the ground wire solved the problem.
If you see in what I write that the problem may be elsewhere and that turning yellow and green could only mask the real reason for the problems, please write to me. Maybe the electrician is wrong and thanks to your ideas, I will gently suggest something to him.

And I really thank you all very much from above and from below for your commitment and help.

ziller wrote:

and this yellow-green zero could only mask the real reason for the problems, please write.

The yellow-green color of the insulation is reserved for the protective conductor, which is not intended to carry operating currents. What you have done now is not only "masking" the problem, but a very possible threat to health and life!!!
Please do not use this installation until the fault is repaired!

I have no choice. I have to use. The cable specialist moved his visit to Monday.

ziller wrote:

I have no choice. I have to use.

You don`t have to do anything.
If you had a problem with a permanent break and lack of power, you would find a specialist today. But since you "only" have a floating zero, then you are downplaying the problem without even realizing the threat.
Typical layman`s approach - there is no electricity, there is a problem; but the current is there, even if it is of poor quality, although there is some "flickering", regardless of the fact that it is at "zero", on which the anti-shock protection may be based - there is no problem.

Your damaged equipment - your money and your business. But remember that on this forum we are aware of the damage you described is seriously risky to the health and life of you and other people using this installation .
The decision is yours.

I understand that maybe this is a threat.

But let`s stick to the topic.

Even on this forum, while browsing topics about differentials, I read about separating the neutral before the fuses into two wires: neutral and protective.

In my case it is exactly the same, only the separation point has moved from the ground floor a few floors higher.

Please stay on topic. This is not the place for lectures on why this or that. You go to school for this purpose, so knowledge from a few posts will not help you.

ziller wrote:

Even on this forum, while browsing topics about differentials, I read about separating the neutral before the fuses into two wires: neutral and protective.

Not zero, but neutral [N]. Protective is PE. However, pay attention to the special function of the PEN cable, it is the one before the separation. Think about what will happen if it is damaged?

retrofood wrote:

Please stay on topic.

"Beginner" section. It`s a bit possible... Or not?

The zero was still in front of the counter. Thank you all again for your help.