What is the danger of an interruption of the neutral wire in the mains?

Every electrician, especially a self-taught person, should know about the consequences of a zero loss in a three-phase and single-phase network. This phenomenon can be very dangerous both for household appliances and for human life. To let you know why the damage to the neutral wire is dangerous and why this mode is emergency, we will consider in detail unfavorable situations and tips for resolving them.

Types of damage

On the riser porch

To begin with, in general terms, consider what the electric network of an urban multi-storey building represents. The power source in this case is a transformer substation, from which wires are stretched to the main switchboard of the building. The voltage in the main shield is three-phase, that is, a network of 380 volts. From here, groups of wires to each apartment are already derived. In the apartments themselves, the network is already single-phase - 220 V. If a common zero break occurs on the riser of the entrance, this can cause the failure of household appliances. This leads to inequality - in a three-phase power circuit, phase imbalance and instead of a symmetrical load, an asymmetric load forms in the four-wire circuit.Electric panel on the floor

In simple words, this can be explained as follows: from the main panel at the entrance to each individual apartment the same voltage is applied - 220 V. If there is a break in the zero wire, it can happen that 300 volts go to one apartment and 170 volts to the other (as an example). The result - overvoltage and "undervoltage" will cause electrical appliances to fail. Usually, if zero damage occurs, equipment with an engine breaks down: washing machine, refrigerator, air conditioning, etc. In addition, a fire may occur, even worse.

What is phase imbalance?

Inside the living room

The very opposite situation can happen when zero breaks in a single-phase 220 Volt network, that is, inside your apartment, private house or in the country. In this case, the consequence may be a person's electric shock. This happens because in the outlet you will have the same phase on both terminals. Now we will tell you what caused the appearance of the so-called second phase.Housing shield

From your input shield, the current passes through the phase wire, and since most consumers of electricity are constantly connected to the network (the same chandelier), when the circuit breaks, the voltage will switch from phase to zero. Result - an electric current will be present in the two holes of the outlet. But this is not the worst thing, because The main danger is that electric shock can occur from any equipment. The reason for this is the wrong grounding system of the network in the apartment or house. If you connect the “ground” in the switchboard to the zero bus (which cannot be done), when you touch the grounded housing of household appliances, you will immediately be shocked. The consequences, as you know, can be dire.Immediately we bring to your attention the correct option for protection against a zero break in the house - a network with grounding system TN-S:Correct grounding in a single-phase 220 V network

380 volt network protection

To summarize the consequences of a zero break in a three-phase and single-phase network, the following should be noted: if the neutral wire is damaged in the riser, the danger spreads to household appliances, and if the working zero is damaged in the apartment itself, the threat will spread to you.

To see what can happen if the zero core breaks, you can in this video:

Visual overview of the fault

How to identify a hazard?

To find the place of damage to the neutral wire, you can use a special tester that can accurately show where the break occurred even under the walls, as shown in the photo below (if the wiring is hidden). About, how to find a wire in the wall, we told in the corresponding article.Search for damage in the wall

Another search option is a visual inspection of the entire circuit. View all wire connections in the switchboard. Perhaps zero burned out on one of the machines, which is not difficult to determine and eliminate. If the breakage of the neutral wire occurred on the riser of the staircase, then it’s not your business and the housing and communal services or a special service that they will call to inspect the power transformer and secondary circuit including will troubleshoot.

How to protect home wiring?

To protect the household electrical network from an open circuit, you need to use special devices: monitoring relays and voltage limiters. We recommend that you connect these devices to the input shield to protect yourself from adverse effects.

Security Overview

Causes of the phenomenon

Well, the last thing I would like to talk about is why there is a zero break in the apartment. There can be many reasons, but the most real, judging by the comments on the forums and personal experience, we can distinguish:

  1. Burning of the neutral wire at power surge or short circuit.
  2. Poor connection lived or poor contact.
  3. Mechanical damage to the line by the elements (for example, in strong winds) or by carelessness of a person during repair work.
  4. The wiring is old and the wires are simply exhausted by time.
  5. Theft or malicious intent (sometimes this happens).

So we examined the types and consequences of a zero break in a three-phase and single-phase network, as well as ways to protect against this phenomenon and tips for troubleshooting. If you do proper grounding in a private house, and also protect the wiring with special devices, then when the zero breaks, no ills will happen!

Also read:

Visual overview of the fault

What is phase imbalance?

Security Overview

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40 comments

  • Ruslan

    I would like to clarify about zero in the apartment. If zero breaks at the entrance to the apartment then all this trouble happens, but if, for example, zero breaks in the room on the chandelier, then there will be no trouble, the phase when the chandelier is turned on will go to the cliff and that's it. Do i understand

    To answer
    • Admin

      Roughly speaking, yes. But note that the voltage in the chandelier will be present, which is also a danger.

      To answer
      • Monhnasan

        Thanks from Mongolia is always happy for you

        To answer
      • Anatoly

        Good day, tell me a big lamp is hanging on a pole. White. Does not light. Having unscrewed the cartridge I checked that there is an indicator on the cartridge. The lamp changed still does not light .. it’s probably not zero or what to look for.?

        To answer
        • Admin

          Hello! The voltage must be measured with a multimeter, then it will become clearer what the reason is.

          To answer
  • Sergei

    Hello.
    1. Do you need to ground the body of the metal shield to the zero bus of the input wire from the pole or to the ground loop?
    2. Is the RCD set before the machines or after?
    3.Cable cross section for automatic machine 24a 2.5 mm. fine?

    To answer
    • Admin

      Hello!
      Regarding the first question, I recommend reading the article https://electroexp.com/en/kak-razdelit-pen-provodnik-soglasno-pue.html
      RCD is placed to a group of machines. If there is only one machine, then there is no difference. Section 2.5 is fine.

      To answer
      • Sergei

        Thanks for the quick response.
        And above in the circuit, zero from the pole and grounding are not connected after all (to prevent the consequences of a zero break). And in that article that you gave the link they are connected! How do you do it? And there is not a word about the grounding of the shield body itself.

        To answer
  • Alexander

    Please correct in the part about zeroing off inside the apartment with a single-phase network: the same phase will be in both conductors (L and N), provided that the consumers are on, but these electrical devices will not work.

    To answer
  • Valentine

    Goodnight. Tell me the solution to my problem. In general, a 3-phase cable is brought to the house. Today I climbed to fix the torn outlet from the wall, I didn’t turn off the machines, and a little bit screwdriver bolted the mount with the phase bar. The machine did not work, well, I think Lando. After adjusting the socket, he plugged in an electrical appliance and there was no cuff. I repeat, the atom did not work, neither the introductory one nor in the switchboard. Vobschem disappeared springs in sockets from the 1st phase. There is light in the rooms because he is from a different phase. The indicator showed the absence of voltage in the shield 1 of the phases, i.e. voltage has stopped flowing from the meter. I threw the jumper from one bag where the phase is on the second, where it disappeared, while disconnecting the wire with the missing phase and took it to the side. Is such a connection dangerous and how to solve the problem with the missing phase? And also, a yellow light blinks on the counter, whether it says reverse or something else. Before that, she had never blinked. Thanks in advance.

    To answer
    • Admin

      Blown fuse in the TP. It is necessary to call an emergency team, they will change.

      To answer
  • Eugene

    After a strong wind at the entrance, all three phases of 230V are in the house and there are power surges and its drop tell me what to do the electrician in the house checked everything, I didn’t find any faults on zero on the input post, is he 15 years old to help understand the reason?

    To answer
  • Alexander

    Good evening. Difrale with RCDs will be able to protect the apartment in the absence of zero on a common riser?

    To answer
    • Petrovich

      RCD is designed to save your life by contact with the device in which the short circuit occurred, and not the device itself.
      Difrele works only in a network with real ground (third wire and two ground loops around the perimeter of the house)

      To answer
  • Anton

    With a break in zero in the riser, the equipment will fail regardless of whether it worked or was just plugged in?

    To answer
    • Petrovich

      Anything that is simply plugged in and is in standby mode (for example, a Chinese set-top box with a remote control) will fail. If you turn on the device with a key switch, the device will remain alive.
      The auto-voltage technique also tolerates a relatively zero breakage. I saw with my own eyes how the TV and monitor, which have a 100-220 V auto-voltage, suffered a voltage surge of 380 V with absolutely no consequences. Apparently, the manufacturer was not greedy, and inserted a surge protection unit inside.
      In this regard, refrigerators of famous brands are very surprised. It seems to cost almost 50 thousand rubles, and there is simply no protection at the input to the electronic control board. As a result, with a break in zero, the refrigerator is candidate No. 1 for failure. If you don’t fix it in a day, then all the products in the trash, then - scandal with his wife, nerves, 100 grams to calm down, respectively - again scandal, then 200 grams. Well, do not leave it at the bottom, but in the morning to work ... In general, for the refrigerator you still need to buy protection from 380 Volts 🙂 There are also household options, and you can put them on the shield. And better both back and forth 🙂
      By the way, all kinds of UPSs, UPSs and other IT stabilizers really save equipment from 380 volts, but as a rule - at the cost of themselves. So decide what matters to you 🙂

      To answer
      • Dmitry

        And what, - to push a varistor with a fuse weakly to "eminent brands" ??

        To answer
  • Petrovich

    The article was written by an amateur
    1. With a zero break inside the apartment, NOTHING will happen. Of course, provided that there are no gross violations in the wiring of the apartment, and all the devices included in the network are working, and do not give short circuits. The lamp in the chandelier is ABSOLUTELY on the drum - the wire will be opened by the switch on the left or on the right. The only difference is that if you climb into the chandelier to change a light bulb or a cartridge, it is better to do so, if the chandelier is opened through a phase wire, then you will not be shocked by the current when you try to hold the cartridge with your hands 🙂
    If you have knocked down the wiring and connected the ground and zero so that you yourself do not remember how, then expect surprises, as they say 🙂 Walk around the apartment in a rubber suit and gloves on a rubber rug :)))
    2. The circuit breaker installed in the shield will not protect your household appliances from anything, in fact. It was created in order to de-energize the apartment in the event of a short circuit and to prevent a fire. Automata are placed mainly on 16A, rarely on 10A. Most household appliances with such currents in a real network simply fail. And only after that - the machine will turn off 🙂 So that every valuable piece of iron should be turned on through a good surge protector, which protects against peak loads and interference. And for good - also provide an individual fuse with a rating based on the voltage and power of the device.
    3. The worst (and most common) is the burning of a common zero in the entrance of the house. Then a voltage of 380 volts instantly appears in the apartments. And this tension literally breaks through most of the established defenses. So, no network filters can save him from it, except those that have protection from 380 Volts. Accordingly, no fuses and thermal fuses have time to trip, because capacitors in power supplies of household appliances respond to voltage faster than fuses to the flowing current. As a result, exploded capacitors at the input in all devices (well, or almost all), including light bulbs. There are ways to protect against this (voltage relay, voltage regulator), but they also like certain “ideal” working conditions, which do not exist in real life, and such devices are not cheap.
    In general, in today's life, when a person wants to turn on a washing machine (2.2 kW), a microwave (2 kW), an iron (2.2 kW), a kettle (2 kW), as well as an air conditioner, TV, computer , a chandelier with 50 halogen bulbs, charging for 3-4 smartphones and a tablet, and so on ... NEED TO BE BEFORE :)))
    Good luck to all!

    To answer
  • Suleiman

    To protect the refrigerator, they sell electronic fuses of the outlet, the principle of its operation when lowering 190V or increasing the fuse will turn off in time and keep it off until the voltage normalizes and turns on after a minute of voltage supply and the equipment is intact. And what happens when the volt decreases, the neutral wire oxidizes the junction at the bolts, washers, it can be checked with a tester with a multimeter.

    To answer
  • Andrew

    Good afternoon! Your advice is really needed.
    At the entrance of electricity to the apartment in front of the electric meter, “zero burned / cut off”, as a result of which the electric meter and the refrigerator engine burned out. The master of Mosenergosbyt recorded this. replaced the electricity meter, cost 9800, refrigerator repair was estimated at 30000 Where to contact and what documents to prepare for compensation?

    I apologize if there are errors in the terminology. I am not a great connoisseur and specialist in the field of electricity.

    To answer
  • Sergei

    Good afternoon! Need your consultation. I changed the wiring in the apartment from aluminum to copper.In the shield, I set the voltage relay and ouzo to each group. And as if he thought that he had completely secured his apartment. But constantly tormented by doubts about entering the apartment. There were 3 wires in the riser pipe, one with a phase in my apartment, one with a phase in the upper apartment and one zero wire TORNED and connected by a nut with a branch to my apartment. He replaced the nuts with new ones, stretched them well, insulated them and ... laid the box with tiles. How bad was this decision? It was not possible to put the liners. Maybe you should put a relay to a neighbor on top or lower apartments are also at risk?

    To answer
    • Sergei

      In particular, I am concerned that over time the walled nut may weaken and then the neutral wire will be torn, with all the consequences described in this article. Walnut type U731M. On one side of the plate brought two ends of torn zero (aluminum), on the other, a copper wire with a cross section of 10 mm.sq

      To answer
      • Admin

        Hello! The fact that you laid the box with tiles is bad. According to the PUE, all connections should be available for maintenance. And yes, it may weaken over time. I understand that the box with this connection was laid in the entrance? Do you know that you should not interfere with something outside your apartment? This should be done by electricians from the management or energy sales company.
        Yes, if the contact weakens, zero can disappear and other apartments will be in danger. If there is a skew, it will be everywhere (or almost everywhere).

        To answer
        • Sergei

          The box was in my apartment, that is, I had access to nuts only, that's why I laid it. I don’t understand the logic of the people who made the wiring in this house, each in the apartment has a metal box in front of the counter in which a branch is made to the counter with nuts, zero is torn everywhere, that is, sooner or later in one of the apartments, contact at zero may weaken and then many may suffer. I still do not understand why the apartments below mine will suffer, the gap will happen for me, and their connection will go to the basement switchboard, and only at the neighbor’s side will the zero hang from the scrap?

          To answer
          • Admin

            And no one said that the neighbors from below would have problems. For those AFTER you on the cable in this phase. Therefore, I wrote that "if there is a skew, it will be everywhere or almost everywhere," that is, just the same implying this issue.

  • Zhumabek

    Good afternoon! Please explain why, when you break off a common zero, the danger is only for devices? After all, if I correctly understand that when a common zero breaks somewhere along the street, my house and the house of a phase neighbor end up in the same serial circuit through a common neutral conductor, in which the total total voltage will be 380 V. And the “zero” conductor is part of this circuit and it is energized. And if the neutral conductor is combined with the protective conductor, then will there be a dangerous voltage on the devices?

    To answer
    • Admin

      Yes it will! But it depends on what kind of power supply scheme you have. If it is two-wire, then the instrument cases are connected to the “earth” contact of the plug. He, in turn, is not connected to anything.

      To answer
  • Ildar

    Hello,
    In the house, a voltage relay is installed for each phase. The relay periodically trips in one phase. After a short time everything works again. Tell me, please, what could be the reason for the frequent operation of the voltage relay? How to define it?

    To answer
  • Carried

    I will share my story. I had a chance to work at the enterprise as a washerman. At my disposal was a Karcher high-pressure apparatus. Washed mainly stainless steel equipment. One fine day I noticed that during work I was a little shocked by electricity, attributed to statics. Then, during washing, I saw barely noticeable sparks between water and the surface. Well, to top it off, when a metal sprayer touched any conductive surface, flashes occurred as during the operation of a welding machine.Then I did not hesitate and called an electrician. He, in turn, noted a zero break in the 380 V plug and said that I was lucky that I did not receive a strong electric shock. And by that time I had worked for several hours with a tattered zero.
    Here is a story. Be careful.

    To answer
  • Ivan

    Good afternoon!
    Tell me, please, whether a breakdown of household appliances is possible under the following circumstances.

    On the street A, a tree (walnut) was trimmed, as a result of which there was a fall of branches on the power transmission line wires, which led to a break in the neutral line (zero). As a result, phase imbalance, interphase circuit, a sharp increase in voltage in the network.

    At the same time, the house in which the failed household appliances were located is located on street B., parallel to street A.

    As follows from the presented connection diagram of streets A, B and C, they are all connected to the same transformer substation No. XXX. These streets are connected to one machine located in the TP. At the beginning of each street there is a 100 A.

    To answer
    • Admin

      The question, of course, is interesting. If zero was re-grounded on street B, then this should not happen. If it was not grounded, or the circuit is bad, there could be a skew in you too ...

      To answer
  • Alex

    And if three wires entered the apartment, one is phase, the other two are not. The voltage between each of them and phase - 220V. Between themselves, these wires ring shortly. That is, two zeros, it turns out, is it easier to land on one bus? Or randomly distribute. They (wires) are all of the same color, and which one is whose one is not clear. Separated separately. But it turns out that on the lands of outlets now Zero. How to be?

    To answer
    • Admin

      In general, the earth will be called as zero. And they will be short ... Call an electrician from the management company, let him figure out where is zero, where is the earth! What kind of cable is used, that he has veins of the same color?

      To answer
  • Vitaliy

    When you touch the phase wire, the indicator shines brightly, the zero wire does not shine, and the ground wire shines but not very bright. What happened to the wiring?

    To answer
  • Victor

    The earth wire may dimly shine from the induced voltage, all wires run side by side, in one bundle, and the earth wire is common at all points. When the consumer is turned on, especially kettles, air conditioners, automatic washing machines, a small voltage is induced on the adjacent adjacent ground wire. This voltage is visible anywhere in the ground wire, the indicator is dimly lit. It is necessary to check the quality of the connection of the grounding wire to the grounding device (grounding circuit).

    To answer
  • Ilya

    Good afternoon! Did repairs in a Soviet house. No grounding. There was only rubbish in the box and it was flooded with concrete ... it was frame soundproofing, which is why it “lengthened” all wires and removed them. But he left all the connections in the same “bundles” as they were. Places did not change. Put a smart switch with a flashlight. Put ice chandelier. At first, the ice of the chandelier did not turn off completely when the switch was turned off. Then he turned it on once, it blinked. Turned off and everything stopped working. When turned on, there was something in the switch and the light did not turn on. Disconnected everything. I began to check. It turns out that there is no voltage on the switch contacts. It turns out this is zero. Even with the open contacts of the switch on those contacts that stick out from the ceiling, on one phase, on the other zero ... it turns out there initially the switch broke the zero, as I understand it?
    Is it possible, then, with external wiring, to bring the phase to the switch from those that stick out of the ceiling? Or is it better to simply remove a new one from the outlet / from the distribution box?
    Thank you in advance!

    To answer
    • Admin

      Good afternoon - the best option is to take the new ones from the outlet or the distribution box.And if everything worked before - then look for the mistake you made when lengthening the wires, maybe when you installed the sound insulation, somewhere the wire was interrupted.

      To answer
  • Oleg

    Good evening. Help me figure out the private sector, three phases and zero on the pole. Being on the same phase, at the beginning of the street, the voltage is 230, and I have 260 reaches 270

    To answer
    • Admin

      Either you are closer to the substation, or there are problems with zero along the line. Contact the power company with this problem, or the manager.

      To answer

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