“Zero” and “ground”: what is the fundamental difference?

Historically, it so happened that in the Russian Federation, as well as in border states, the grounding principle is used, when the neutral conductor is connected to the ground loop. Many people may have a “legitimate” question: if they are in contact with each other, then why pull so many wires - it’s enough to run a double wire everywhere (phase and zero line) and it will be possible to ground through the zero wire! However, this formulation of the question hides one technical nuance that turns this solution not only into a useless toy, but in some cases into a rather dangerous undertaking.

Zero and ground - what is the fundamental difference?

For those who are impatient and who like to “peek into the answer,” I will a priori tell you a “secret” - the fundamental idea is where the neutral wire is connected to ground. The option of connecting them directly inside the socket, connecting the grounding conductor (yellow-green wire) to the neutral conductor (blue wire), will not be correct. Such a grounding scheme will conflict with the requirements of the PUE. As a result, people will not be protected from electric shock; moreover, even more safety problems will be added.

The PUE, without any options, clearly states what the grounding conductor should be like. It must be a continuous wire, without any disconnecting elements - relays, fuses, switches, and also, for example, by disconnecting the electrical plug from the outlet.

Once this basic requirement stipulated in the PEU is violated, grounding from reliable protection of a person from electric shock turns into a useless fiction. But the problems, as theory teaches and practice shows, do not end there! If you still try to give the neutral wire grounding functions, then it is possible that the body of the refrigerator, microwave oven or other household appliances will be energized. This is explained by the fact that an electric current flows along the neutral wire with a corresponding voltage drop, the magnitude of which can be determined by multiplying the current strength by the conductor resistance in the interval between the measured location and the true grounding point. Moreover, the magnitude of such voltage can be characterized by tens of volts, that is, it can be dangerous for humans (at the limit - fatal!).

Zero and ground - what is the fundamental difference?

It remains to sum up some results and place emphasis. What is the fundamental difference between “zero” and “ground”? The fact is that current flows through the neutral wire and switches, the same input circuit breakers, are connected to it. That is, if we want to have “earth” in the form of a continuous vein, we must:

  • in multi-storey apartment buildings: connect to a special earthen conductor in the electrical tunnel;
  • for an individual residential cottage: the connection point should be the input circuit breaker, more precisely, its neutral wire at the input, which runs through the air or underground cable from the step-down transformer closest to the house, and the cross-section of the neutral wire should be at least ten square millimeters for copper wire and 16 mm2 – for an aluminum core (see the corresponding paragraph in the PUE).

Any other place behind the input machine cannot be used as a “ground”, therefore nothing, from metal blanks buried near the house to the body of the electrical panel itself, can be considered as such.

Never forget about the rules set out in the PES. According to them, you should be guided by an elementary but true rule: when you are not sure that this particular wire is “ground,” you should not connect anything to it except a 30 mA residual current device (RCD), which operates instantly, unlike a circuit breaker. As you know, God protects those who are careful!

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Comments (149)
  1. Nikolai.
    #1 Nikolai. Guests 6 January 2019 15:57
    17
    It’s high time to forget what grounding and grounding are. Today's houses are powered by one wire. In other words, only the phase enters the house from the panel. And the neutral wires come out of the apartment into the panel and are hung on the neutral piece, which “sits” on the neutral wire of the main cable, and that in turn is hung on the grounding bolt. All. There is no need to think about anything else. This is done to prevent electrical energy from being stolen by conducting the grounding bus separately from the main circuit.
    But even this trick can be bypassed and by setting up “your own” grounding bus, “hanging all the needs from your consumers on it. But how to do this is almost impossible. It will be necessary to lay all the neutral wires, lay new ones, “your own”. you will be figured out.
    1. Evgen
      #2 Evgen Guests 6 January 2019 19:51
      51
      “It’s high time to forget what grounding and grounding are,” what did you even say?

      there is grounding and there is grounding, and finally in this article there is more nonsense written that explains something.
      Let me tell you briefly, the zero is always grounded, in old houses it is grounded at a substation and there is no ground in such houses, because the “scoop” always saved on everything, it was a pity for him to also extend a grounding wire at the entrance to all the apartments, but now the simplest scheme is this the zero is grounded already in the switchgear at the entrance and a separate grounding is drawn from it. And everyone should switch to this system a long time ago!!! only, as usual, the fucking economy does not allow all people to normally use imported household appliances, because they always have to!! need land!! , and we are half in the Soviet Union, but we enjoy the benefits of Western civilization.
      1. gogol
        #3 gogol Guests 7 January 2019 14:50
        31
        Dear! We have enjoyed the benefits of civilization. until the middle of the 19th century. And now we are reaping the fruits of immorality and complete degradation of humanity
        1. Yuri
          #4 Yuri Guests 7 July 2023 12:57
          1
          And then there was a nuclear war? smile
      2. Boris
        #5 Boris Guests January 9, 2019 10:55
        17
        When did we have an RCD? Since then, the need for a third wire has arisen. This is the 90s. The absence of a 3rd wire is not a “soviet” saving, it is a theoretically unacceptable waste of non-ferrous metal. For what purposes was the 3rd wire needed? Do you think there is a solidly grounded neutral everywhere in the world? And if linear 220, but in a triangle? In the United States, in general, in the household sector, food comes from the “pig” brand, and has been for a long time. You can try working with household appliances used in Japan or the USA, especially if they are powered from the middle point of the same “pig”.
      3. RRR
        #6 RRR Guests 9 January 2019 13:59
        12
        You write nonsense without understanding the essence of the issue. Don’t mislead people
      4. Crocodile
        #7 Crocodile Guests January 13, 2019 03:32
        43
        A dustpan is a good tool for cleaning up trash. Unfortunately, I can’t imagine what kind of dustpan you need to remove the garbage from your head.
    2. manolis
      #8 manolis Guests 6 January 2019 20:49
      2
      Take the plus from the shield and do not take it into the house but mines with ze
      1. Guest Vlad
        #9 Guest Vlad Guests January 9, 2019 01:28
        24
        Another “craftsman” whose house is powered by constant voltage. Plus and minus in DC circuits. The house has alternating current. Zero and Phase.
        1. SlOPS
          #10 SlOPS Guests 14 January 2019 18:53
          6
          The house has alternating current, 3 phases with a displacement at an angle of 120 degrees (total 380 volts) and in the center there is a zero, which is essentially a flow bus. The difference between this bus and any of the phases gives 220 (230) volts.
      2. Vladmir
        #11 Vladmir Guests January 15, 2019 11:09
        1
        Well, you....oh, what a dense one!
      3. vano55
        #12 vano55 Guests 1 March 2019 20:35
        3
        Where did you find (+), in AC?
    3. Mitya
      #13 Mitya Guests 10 January 2019 15:39
      15
      PUE does not care about finances - this is not his goal, but his safety. Just one example: If 0 breaks, then when the ground is short-circuited, the body (for example, a refrigerator) is under voltage no more or less than 220V!!!
      1. Andronus
        #14 Andronus Guests 13 January 2019 20:10
        1
        Voltage is the potential difference at the ends of the conductor, and due to the resistance of the consumer (refrigerator), the difference is reduced and the output to the housing will be no more than 100 volts.
        1. Guest Alexander
          #15 Guest Alexander Guests January 23, 2019 00:27
          8
          To throw away the skates, 100 V is enough
      2. one
        #16 one Guests 21 January 2019 15:00
        7
        Buddy, in order for the body of the refrigerator to become energized, you must first conduct this voltage to the body or break through the insulation and connect the compressor motor in such a clever way that the breakdown goes to the body..
      3. Mark
        #17 Mark Guests 7 March 2019 23:12
        0
        It is precisely in the PUE that it is stated that the refrigerator body (an electrical device with double insulation) does not require grounding.
    4. Guest Mikhail
      #18 Guest Mikhail Guests 12 January 2019 17:50
      7
      in order to steal as you suggest, you need to open the seal on the meter and swap 0 and phase, and this is easily determined because the meter will stand, if you decide to shift the phase and rotate the meter in the opposite direction, then this is effective only on pure mechanics. electronic systems that are either optocouplers or hall sensors on the drum direction of rotation in general
    5. Ruslan
      #19 Ruslan Guests January 26, 2019 11:39
      4
      Nikolay, you are clearly not an expert in the electrical power industry, so please, do not make up a gag and do not mislead ordinary people!
    6. Guest Alexey
      #20 Guest Alexey Guests 2 March 2019 23:31
      4
      If you don’t know anything about electrical engineering, then don’t write anything, because with your nonsense you are exposing people to mortal danger. It should have been written like this - “only the phase enters the house from the panel”!
      What follows is just complete nonsense. In an apartment building, three phase conductors are laid in the riser, one neutral, one grounding. In the ISU (input distribution device), the neutral and grounding are connected to different buses, between which a jumper is placed (!), because the zero at the input must be re-grounded, which is done by connecting the local grounding loop of the building to the grounding bus. For private houses the principle is the same: the zero at the input must be re-grounded, i.e. connected to the local (for a given house) grounding circuit, starting from this point the neutral working and protective conductors must be strictly separated in all sections of the circuit.
    7. Evgeny Pavlov
      #21 Evgeny Pavlov Guests 15 September 2020 16:07
      4
      I understand that as an electrician you worked with single-phase appliances, your level is limited to installing electrical appliances in apartments. If you take a three-phase network and a high-power load with currents of the order of above 100 A, then you will definitely need an honest earth. It is also necessary when you need to have real O for power supplies of sensitive devices. A neutral, which can be made in any way and in a clumsy manner and in which there may be potential, is not suitable for this, especially since along the way there may be all sorts of connections (terminals, twists, etc.) that can unexpectedly create problems and have high resistance.It is precisely to eliminate surprises, to pass a large current, to ensure complete zero and guaranteed low resistance, as well as the absence of a large number of intermediate connection points, that the ground is made. And it is critically important in critical (precise, powerful, etc.) equipment. To connect a light bulb, you can do without a ground, but for a three-phase power source with precise control of the signal shape/frequency/phase/amplitude you cannot do without a ground.
  2. Egor
    #22 Egor Guests 6 January 2019 18:28
    79
    The author is trying to reveal a topic about which he has no idea. He refers to the PUE, but he, it seems, did not look into them. Has no idea what the difference is between grounding and grounding. Where is grounding used and where is grounding used? In general, the author has a mess in his head, he took a topic in which he is not competent.
    1. YURICH
      #23 YURICH Guests 8 January 2019 21:49
      11
      5+. I completely agree.
    2. Semyon
      #24 Semyon Guests 9 January 2019 10:05
      9
      I completely agree. The author of the article did not understand the topic. In general, such things, especially those related to electrics, should be written by people with a technical education.
      1. Guest Alexander
        #25 Guest Alexander Guests 9 January 2019 19:44
        9
        Even having a higher education in your specialty also does not always give you the right to express your opinion. At our enterprise there was a head of the electrical department who was very proud that he took part in the construction (not in construction, but it seems in commissioning) of some kind of nuclear power plant in Iran. So, he had not heard that there is a concept of “touch voltage”, but this concept is present either in the PTB or in the Electrical Installation Rules somewhere next to the concept of “step voltage”. And it worked fine. And my wife, a graduate of Moscow Higher Technical University named after.Bauman, qualified as an electrical engineer, when I wrote my diploma, I calculated something like the resistance of a grounding device. But she could hardly explain it after a couple of years, but she rose to the position of leading engineer at a research institute. So you don’t need to know many things at all. You just need to do it according to the project, and designers must know the rules and must follow them.
        1. Ruslan
          #26 Ruslan Guests January 26, 2019 11:47
          3
          A high position is not always an indicator of knowledge and intelligence - thank you for confirming this using the example of your boss and your own wife!
  3. Pavel Petrovich
    #27 Pavel Petrovich Guests 6 January 2019 18:32
    40
    Guys. And the one who wrote this article and many commentators have no idea what they are writing about. You must first be certified for at least group III electrical safety, then write something. There are no other concepts in electrical engineering and electrical safety other than those written in the rules!!!
  4. sanek
    #28 sanek Guests 6 January 2019 18:44
    5
    all this is just cool, of course, safety is a big deal, but don’t think that our grandfathers were stupider than us, even now in most private houses there is no real zero; it is connected to the zeros on the first support; it enters the house through two wires; what kind of grounding is it? just beautiful words about how it should be like everything in our country
  5. Gregory
    #29 Gregory Guests 6 January 2019 18:45
    2
    I don’t understand one thing, the current is alternating, that is, zero and phase must alternate places. That is, if the current really flows, then in one direction, then the other. And zero is not zero at all 1/25 sec. What do I understand wrong?
    1. Guest Alexey
      #30 Guest Alexey Guests 6 January 2019 21:20
      11
      You don't understand it wrong. Nobody changes places there. Zero is zero, and the voltage level on the second wire (phase) changes relative to zero. Sometimes more of him, sometimes less.Well, it's that simple.
      1. Den Kol
        #31 Den Kol Guests January 8, 2019 00:39
        0
        Can not understand anything.
        1. Guest Vladimir
          #32 Guest Vladimir Guests January 15, 2019 11:16
          4
          Well, for example, a glass, we consider the bottom is zero, the upper cut is max voltage, I still can’t laugh... making fun of your stupid questions is a godly thing
      2. Guest Vlad
        #33 Guest Vlad Guests January 9, 2019 01:35
        2
        What voltage level is changing? Take a voltmeter and measure. Between zero and phase 220 volts, between any two phases 380 volts. Don't talk nonsense.
        1. Guest Vladimir
          #34 Guest Vladimir Guests 9 January 2019 14:02
          3
          YYYY. The amplitude value disappears as it changes. And it’s not 220 or 380 V. But it’s working, yes, just as I said, it’s almost like that.
        2. Guest Alexander
          #35 Guest Alexander Guests 13 January 2019 20:08
          3
          What if you take an oscilloscope instead of a voltmeter?
        3. Andronus
          #36 Andronus Guests 13 January 2019 20:15
          1
          Yes, it’s not the voltage that changes, but the potential
    2. Guest Vlad
      #37 Guest Vlad Guests January 9, 2019 01:33
      10
      In alternating current))) it is not the phase and zero that change places, but the phase follows a sinusoid with an oscillation frequency of 50 times per second. What is the frequency of the current heard? Indicated in Hertz. In our network we have a frequency of 50 Hz and a voltage of 220 Volts; in the USA and Europe we have a frequency of 60 Hz and a voltage of 127 Volts.
      1. Nikolay Polozok
        #38 Nikolay Polozok Guests January 9, 2019 09:19
        2
        In the USA, the sockets are 110V 60 Hz, and in Europe they are 230V 60 Hz.
      2. Andrey
        #39 Andrey Guests 9 January 2019 22:32
        2
        ABOUT! This is a sensible comment, not blah blah, somewhere close to the true one)
    3. Guest Sergey
      #40 Guest Sergey Guests January 14, 2019 00:10
      2
      If there are only two wires, then you understand correctly, back and forth every second 50 times, and there is no direction, the wires are equal. But in reality there is a third conductor - the ground, (well, or the static capacitance of the body) and relative to it, zero is always zero, and the phase is alternating voltage.
  6. Guest Sergey
    #41 Guest Sergey Guests 6 January 2019 18:49
    3
    In switching power supplies, in particular, computers, when using Euro sockets, voltage division is carried out by capacitors, the middle point of which is connected to the ground, and 220 is supplied to the capacitors themselves through a bridge. Will this be correct if on one half of the divider the voltages are distributed between Zero and Earth, which in principle is equal to 0 and only when the phases are imbalanced reaches several volts. and on the other shoulder - everything else is from 314V?
    1. Guest Vlad
      #42 Guest Vlad Guests January 9, 2019 01:38
      12
      The capacitor NEVER shared any voltage. Where do you get all this from? Capacitors are designed to smooth out ripple in the power supply.
      1. RRR
        #43 RRR Guests 9 January 2019 14:01
        8
        And of course you haven’t heard about a capacitive voltage divider
      2. Andrey
        #44 Andrey Guests 9 January 2019 22:35
        0
        Accurate and correct answer) In my opinion, that friend was “a little confused” about power supplies.
  7. Ivan Gennadievich Gordienko
    #45 Ivan Gennadievich Gordienko Guests 6 January 2019 19:04
    12
    Hmm, the electricians have gathered! Study the PUE and carefully study why protective grounding is needed! It’s time to bury the TN-S method long ago
    1. Guest Vlad
      #46 Guest Vlad Guests January 9, 2019 01:39
      3
      TN-S-C has been used for so long
    2. Guest Victor
      #47 Guest Victor Guests January 9, 2019 06:33
      7
      Dear, haven’t you confused anything, TN-S? Maybe TN-C?
  8. Guest Sergey
    #48 Guest Sergey Guests 6 January 2019 19:14
    3
    judging by your diagram, what prevents you from taking the ground in front of the ouzo or the introductory contact to the ouzo, flow one?)))) either I’m a fool or the skis don’t go on asphalt
    1. Guest Alex
      #49 Guest Alex Guests 11 January 2019 14:09
      18
      Due to my inexperience (I had just started working as an electrician), I did just that back in 2004. And he almost burned down his own apartment. This picture is still before my eyes, although so many years have passed...
      We then lived in an old building, built in the 30s (a wooden house, plastered inside). And we had the usual traffic jams (or rather, one per “phase”). At that time, I had already been working as an electrician for a year and a half, I thought that I knew and could do everything, “I’m a genius” and all that. I decided to install “European sockets” in the kitchen, and at the same time change the plugs for automatic machines, and install an RCD (since at the same time as replacing the wiring in the kitchen, we equipped a shower with an instantaneous water heater (for those who don’t know, in those old houses there are similar “blessings of civilization” never existed, they “finished everything” themselves)). Well, I installed an RCD, automatic machines, divided the lines into the kitchen and into the rooms... I placed the grounding conductor from the “Euro sockets” and the instantaneous water heater at the input of the RCD, under one terminal with the neutral wire from the meter. And “for reliability” under the same terminal I put (damn, now it’s funny to me what I’m writing and from the fact that I was “fenced” then) a twisted pair of wires of 1.5 “squares” and connected it at the other end with... a heating battery in the kitchen, and even attached a shower tray. I checked the functionality of the RCD with a “test lamp” (the leakage current of the lamp was sufficient), regarding the battery, the sump and the “phase”, the RCD worked correctly, “everyone was happy, everyone “laughed”... Exactly until the moment “the thunder struck ": in our area of ​​the city a violent construction, all the old houses were demolished (including mine after some time), the area began to be rebuilt, new high-rise buildings, everything. And one Saturday evening, the builders managed to cut the cable that powered our house from the transformer substation. Their foreman came running with a team of hard workers, they reassured everyone that now the temporary construction site for the house would be abandoned, and on weekdays, together with the network workers, they would restore everything.We disconnected the damaged cable from the input cabinet of our house, connected our own, powered it from the construction site... But, apparently, the cross-section of our temporary shed was chosen in the wrong way. Although the house is old, with 8 apartments, everyone has modern equipment, the load is decent... We were smoking in the kitchen at that moment. First the light came on. For three seconds. Then there was a momentary subsidence that the lamps were barely burning. After that, they flashed very brightly for a few more seconds and went out, and a terrible crash was heard from our corridor. We jump out and see how our counter is blazing with an open flame, but it’s not too bad! And above the counter there is a mezzanine (wooden), around there is dry old wallpaper, next to the right there is a freshly painted casing of the front door... And all this is already licking fire, and there is a lot of smoke in the whole apartment. Literally in a matter of seconds... If we had not been at home at that moment, the whole house would have received amba, not just us. They filled everything with water from the kettle and mugs, ran out into the street, shouted to the builders not to turn anything on yet. Everyone is in shock, what the hell...!?.. The foreman came running... We ventilated the apartment from the smoke, let's go home... That wire of mine that went to the heating radiator and shower tray with earth simply melted along its entire length ... I opened the smoky plastic box where the RCD with machine guns stood, everything was scorched, but it seemed to be alive. I threw away all the “earth” conductors from the entrance of the RCD under the supervision of a foreman who had suspicions that we were stealing electricity (although this was not the case, because it was “ala potential equalization done through ...”)... The builders dragged the cable with conductors of a larger cross-section and powered the house, without incident. When the shock passed, the realization of the mistake came.The trick is that many people forget (including me at that moment) that in our country the residential sector (and not only) is powered by three phases using a neutral conductor. And if the load across the phases is not uniform (and in the residential sector this is always the case), then current begins to flow in the neutral wire and the voltage jumps (I explain this in a simple way) - in the overloaded phase the voltage sags, in the underloaded phase, on the contrary, it jumps (occurs phase imbalance). And if the neutral conductor has poor contact with the neutral, or a weak cross-section, then under a good load it burns out... which is what ultimately happened: first (according to the builders) their zero burned out, and after a couple of seconds it broke out on mine in the apartment, because for all eight apartments, including mine, the neutral wire was my “thin” wire, connected to the heating battery and connected to the RCD input... Therefore, comrades, learn from other people’s mistakes. They can become (God forbid!) fatal...
      Now we have been living in a new building for a long time; when we moved in, I redid the municipal renovation of the apartment, along with the electrics, and installed a voltage relay (UVR) in the apartment panel, which has already saved us from surges more than once. Many people are surprised - why do you need a UZM in a new building, because all the wiring is modern and new? Error again! Yes, everything is new for me. And the house is connected to a TP, built in the 80s. And the entire energy supply system must always be considered in its entirety, “from start to finish,” as a single whole. And if some place of this “single whole” is “narrow”, then it is better to play it safe so that later it will not be excruciatingly painful, especially since, as I wrote above, the UZM has worked more than once.And in a neighboring new building, when carrying out welding work in one of the apartments, the zero on one of the risers did burn out (I don’t know the exact details) and our management company received a lot of lawsuits from the owners of apartments with burnt equipment...
      1. one
        #50 one Guests 21 January 2019 15:05
        3
        in order to skew the phases created by the generator of the power plant, you need to drop the load in the region of 10% of the generated power... what kind of equipment did you have in your house, a hyper mine farm or something?
      2. guest
        #51 guest Guests 25 January 2019 15:40
        5
        I finished reading, I wasn’t lazy. Leo Tolstoy and Fyodor Mikhailovich Dostoevsky resting on the sidelines
      3. Valdemar
        #52 Valdemar Guests 22 April 2023 13:22
        0
        You got burned out because the “electricians” mixed up the F and 0 inputs, in other words, the phase went through the wires for 0, where they didn’t install the machines and neutralized the wires with batteries and all sorts of metal risers (a very big mistake). And all these wires just burned out, those phase-grounding-0 karat.
  9. Guest Vladimir
    #53 Guest Vladimir Guests 6 January 2019 19:41
    14
    It would be better to write, if so smart, how to distinguish the neutral wire from the ground wire in a three-core cable, where all the cores have the same insulation color. These were laid in the early 80s in apartment buildings for electric stoves
    1. Guest Sergey
      #54 Guest Sergey Guests January 14, 2019 00:16
      3
      We need to find where the second tail is attached. Or cut off the electricity in the house - the grounding is not broken by the switch, so at zero there will be a small amount of interference, but at ground level there will be none.
  10. Vaik
    #55 Vaik Guests 6 January 2019 19:47
    6
    0.4 kV NETWORK with solidly grounded neutral. There is no difference, ground, zero. Don't mislead people
    1. Guest Vlad
      #56 Guest Vlad Guests January 9, 2019 01:43
      6
      There is a difference.Is it just that the neutral is solidly grounded? Where do zero and ground come together? At the substation or in the input switchboard of the ASU, and as it is correctly written in the same PUE, Chapter 7, re-combining the zero working and zero protective conductors along the distribution of energy is strictly PROHIBITED!!!