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

January 6, 2019 Electronics 613 254 144

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

Zero and earth, what is the fundamental difference

For those who can’t wait, and who like to “look back,” a priori I will say “secret” - the fundamental idea is where the ground wire connects to ground. The option of connecting them directly inside the outlet, connecting the grounding conductor (yellow-green wire) to the zero (blue wire), will not be true. Such a grounding circuit will conflict with the requirements of the PUE. As a result, there will be no protection for people from electric shock; moreover, even more security problems will be added.
In the PUE, without any options, it is unambiguously prescribed what the grounding conductor should be. It should be a continuous wire, without any disconnecting elements - relays, fuses, switches, and also, let’s say, by disconnecting the electric plug from the outlet.
It is worth violating this basic requirement stipulated in the EMP - and grounding from reliable protection of a person from electric shock turns into a useless fiction. But the problems on this, as the theory teaches, and practice shows, do not end there! If you still try to give grounding functions to the zero wire, then the possibility is not excluded that the case of the refrigerator, microwave or other household appliances will be energized. This is due to the fact that an electric current flows with a corresponding voltage drop through a zero wire, the value of which can be determined by multiplying the current strength by the resistance index of the conductor in the gap between the measured location and the genuine grounding point. Moreover, the magnitude of such a voltage can be characterized by tens of volts, that is, it can be dangerous to humans (in the limit - deadly!).

It remains to draw some conclusions and put emphasis. What is the fundamental difference between “zero” and “earth”? The fact that current flows through the neutral wire and switches are connected to it, are the same input machines. That is, if we want to have "land" in the form of a continuous vein, we must:

in multi-storey apartment buildings: connect to a special earth conductor in an electric tunnel;
for an individual residential cottage: the connection point should be an input automatic machine, more precisely, its zero wire at the entrance, which stretches through the air or underground cable from the step-down transformer nearest to the house, and the cross-section of the zero wire should be at least ten square millimeters for copper wire and 16 mm2 - for aluminum core (see the relevant paragraph in the PUE).

Any other place behind the introductory machine cannot be used as "ground", therefore nothing can be considered as such from metal ingots dug near the house to the body of the electrical panel itself.
Never forget the rules set out in the PES.According to them, one should be guided by an elementary, but true rule: when there is no certainty that this particular wire is “ground”, you should not connect anything except an 30 mA residual current device, which It works instantly, unlike a circuit breaker. God knows how to keep safe!

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Comments (144)

#51 Guest Alexander Guests January 25, 2019 11:34
0

The author is so confused that it is very difficult to understand his thoughts.
It seems that the author - non-electrician, or self-taught, took up his own business.
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#52 Sergey Shamarin Guests January 25, 2019 2:16 p.m.
2

Well, nonsense, the author clearly began to read the PUE, and he finished "PES". The fundamental difference between the "0" - wire (neutral) and ground in their purpose. Grounding - protection that connects the housing of the appliance to the ground loop, which protects a person from fatal electric shock in case of insulation failure and phase contact on the housing. 0-wire, a structural element involved in the generation of alternating current electricity with voltage of 220V (phase 380V and 0 give these same 220V.) There are other functions of the neutral wire associated with its design features (isolated neutral, grounded neutral, etc.) , but this does not apply to this issue.
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1. #53 Andrei Guests January 27, 2019 1:20 p.m.
  0
  
  The fundamental difference between the ground wire and the neutral wire in their potential relative to the ground.
  In order to understand this, it is necessary to count at least once in a lifetime conductors on an overhead power line (VL) with a voltage of 0.4 kV and any higher-voltage VL. To reduce the total mass of overhead lines, high-voltage overhead lines do not contain zero wire at all - in technical language, this is called "power supply with reduced neutral." VL-0.4 have four or five conductors - three phases, zero and optionally a phase wire for powering street lighting. VL-6 (now VL-10), VL-35 and beyond - three phase wires (plus a ground wire from above, sometimes mistaken for a neutral wire - no, this is not "zero", this is protection against lightning). And the step-down transformer 10 (previously - 6) kV / 0.4 kV, in addition to the function of undervoltage, also has the function of neutral recovery - with a certain design of the transformer’s magnetic circuit, if you connect its secondary windings with a “star”, then - due to a phase shift in three phase conductors of 120 degrees in the center of the "star", the potential will be zero - this is the "restored neutral".
  But!
  So it will be when one condition is fulfilled - the equality of magnetic fluxes in the secondary windings, and it will be fulfilled only if the currents in them are equal, that is, with a strictly identical load on each phase.
  There is a problem - it is impossible to provide. :)
  As a result, the neutral potential relative to the Earth potential can be from zero (with equal currents) to 30-40 volts. With a strong phase imbalance - up to 80 volts, but this will already cause an alarm.
  Imagine for yourself what will happen if you touch the nullified case of the refrigerator, and on it - 40 volts. You will shy. And if you are not lucky (you got wet out of the shower and climbed for a cold beer), then he will die. 40 volts is a lot, believe me. All human resistance is skin resistance, if you pierce your fingers with a needle, then a deadly current of 100 mA can be obtained from the “Krona” with a voltage of 9 volts.
  Concerning all household appliances must have a connection of metal parts in contact with the human body, with the so-called "electrotechnical land". This is not exactly the same as the "radio earth", for details - in the EMP.
  
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#54 Guest Vladislav Guests January 25, 2019 18:30
0

KG / AM
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#55 Ivan Guests January 27, 2019 3:59 p.m.
1

In the Soviet Union, connection schemes for residential buildings with the so-called “dead-grounded neutral” is when the neutral bus of the power supply transformer was grounded on the ground circuit of the substation. So in the USSR there were zero and ground wires as if together. This was done, yes, most likely from economy, aluminum wires were made from nowhere else they are not used in the world (in the GDR I saw an aluminum wire copper-plated from above, it was not easy to work with such ones, they were very brittle) In general, I can say that the USSR had the most reliable electric networks in the world, because when calculating these networks they took into account the overload 200% .. .
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#56 Sanya Guests January 28, 2019 at 09:58 a.m.
0

Oh bl ... how many disputes are there, in simple words it will be. Consumption to houses comes from the transformer. 3 wires are suitable for the transformer (all phases, there is no zero) in the transformer the voltage drops to 380 volts (3 phases) the question is, where does 220 come from ? And this is the ground loop around the transformer. Here with respect to this earth it turns out 220. But only after going through houses this zero is partially lost and it gets a little voltage on it, if you make good grounding near the house and check the voltage between your ground and zero then the voltage will be be present.
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#57 Anton Guests January 28, 2019 3:13 p.m.
0

I do not agree with the grounding of private houses. Making earth from scratch is nonsense. At least until the opening machine, at least after. Earth is called "earth" for that. "Earth" must be done, burying the "blanks" in the ground! But, do everything wisely.
It is necessary to bury so that, as a result, between the ground wire and the zero wire, the resistance would be no more than 40 Ohms. Ideally, 29 ohms. Then the "earth" is considered working and the current will not flow through the human body, but into the "earth". Accordingly, the RCD will work correctly.
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#58 Alexander Efimovskikh Guests January 30, 2019 5:11 p.m.
1

I’m not a cool electrician, electrician or electrician, or even somewhere ... well, but from practice I know that to scold the scoop, it’s better to look in the mirror. The contours in comfortable houses were carried out according to the project, although later there were projects in which the circuit was absent, except for the gag. And the builders, concrete workers, and others jerked and not sickly. Since it is not voltage that kills, if I'm not mistaken, but the current, and the tool when the working zero is broken, fail. And they talk more correctly about working zero and zero protection, which in the shields have different n LANKI. Now, for new, although for a long time, five wires are being drawn and the cables should be used, also five-wire, and three wires of 380v, for wiring around the house at 220v. But, so that only one phase is fed into the house, this is news for me although the kolymers often use this method when they steal electricity, forcedly or deliberately. Yes, and often had to deal with a moronic installation, when the circuit breakers are put on working zero, which should sit in phase and exclude the electrician and others from getting under voltage when the switch is turned off.
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#59 sergej-49 Guests February 2, 2019 11:01 p.m.
0

Current flows through the "Zero", your safety through grounding.
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#60 Guest Nikolay Guests February 3, 2019 2:58 p.m.
0

The only REAL EARTHING can be considered only a grounding circuit consisting of at least 2 electrodes driven into the ground by at least 2 meters and interconnected by a steel strip of 3 mm x 15 mm by electric welding. And a grounding conductor is screwed to it in a visible place, which ideally is attached to the body of the appliance also with a bolt and nut. For consumers of low power (computer, TV, etc.), it is permissible to use three-wire wiring in which the ground electrode of the outlet is connected to the ground loop. In no case DO NOT connect the ground electrode of the outlet to the neutral wire.In my practice there was a case of defeat of an email. current, when an electrician mixed up the phase and zero when reconnecting the house to the network, and earlier another electrician made a “zeroing” in a three-wire outlet. In my house I use a three-wire network and a grounding circuit of 4 pins, 2.5 meters clogged into the ground. The measured resistance to current spreading is less than 0.1 Ohms (norm no more than 4 Ohms).
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#61 Guest Alexander Guests February 7, 2019 10:39
0

I have an electronic meter. The voltage in the network is 180 volts. And to increase the voltage, I made a circuit and threw a zero wire on it. The voltage increased, I was satisfied, but when I took the meter reading on the 1st, my jaw dropped. The counter got me an extra 1000 kW. And I had to pay. It turns out that the electronic meter, when switching to the ground, begins to wind the light several times faster.
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1. #62 Guest Roma Guests March 6, 2019 10:28 p.m.
  0
  
  Rave. The voltage just increased, and with it the power of all your consumers. And since the power has increased, it means that the energy consumption that the meter took into account has also increased.
  
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  1. #63 Konstantin Guests March 9, 2019 00:24
    0
    
    general electrician. no problem. just put the ground to the meter. and the people who burned are not to blame just the repairmen put the phase on the former zero. what is the argument?
    
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