What is protective grounding and how does it work

The article is good and helpful. Thanks!

The most popular question for electricians is "How is grounding different from grounding?". Not every experienced electrician can properly explain what the differences are. So, protective grounding is needed to create a reliable electrical connection with a sufficiently small resistance between the case of the power receiver protected by it and the ground. The grounding resistance should be several times less than the resistance of the human body, so that as a result of a person touching the core of the damaged power supply, a harmless current would pass through the body.

Protective grounding is necessary for the electrical connection of all metal cases and structures with a grounded neutral of the transformer. Protective grounding turns any short circuit to the case into a short circuit, which leads to the shutdown of the emergency section by a machine or fuse. Here, the main factor is the condition under which the phase-zero circuit has such a low resistance that the short circuit current in the emergency section is sufficient to disconnect the nearest machine or melt the fuse fuse.

Zeroing is the connection of the housings of electrical appliances and machines that may be energized with a grounded neutral wire. This leads to the fact that a short circuit to the body of an electrical appliance or machine turns into a short circuit of this phase with a neutral wire. As a result, a large short-circuit current causes the protection to trip and the damaged installation is shut down. Zero protective conductor can be steel pipes of electrical wiring, as well as neutral wires, which should not have fuses and switches. Zero working and zero protective conductors usually come from the substation where the transformer core is grounded.

Thank you article is good. Please tell me how to ground outlets in offices without changing the wiring. Thanks in advance!

Elena, without upgrading the wiring and transferring it to the TN-S system, well, or at least the TN-C-S should not be able to ground outlets in offices. What this is fraught with, you can see here: https://e.imadeself.com/en/main/voprosy/426-uzo-v-dvuhprovodke.html

Three phases come to my house and zero can I do grounding separately to my e-mails. devices and how to do it competently? Thanks!

I will criticize the article and some reviews :), because there are a lot of inaccuracies in it.

Firstly, it should be noted that a system with a grounded neutral is used not only in Russia, but also in most countries of the world. This is if you take the voltage up to 1000 V, used in everyday life.

Now consider a few quotes.

It’s more correct to say “neutral point of the transformer windings”, because someone above has already repeated even further from the truth :) that the core of the transformer is grounded.

Again an inaccuracy. It is imperative to indicate exactly which “accidental undervoltage” is meant. Since the BASIC protection measures will be different. For example, for random direct touch to live parts main protection is insulation.

And for an indirect touch (that is, when we did not put a nail in the socket :), but touched the body of the washing machine, which suddenly turned out to be energized as a result of damage to the insulation) - the main measure of protection will again be not protective grounding a auto power off (see GOST R 50571.3-94 Electrical installations of buildings. Protection against electric shock.

Item 413.

I.e, The main measure of protection is turning off the power., and protective grounding is just a means of achieving this shutdown. There is no properly selected protection - zeroing will not help. Great will be the resistance of the phase-zero loop to trip the circuit breaker - and zeroing will not help.

If earlier there were inaccuracies small enough, then here (excuse me!) A very gross mistake. The resistance of the phase-zero loop cannot be reduced in any way when performing protective grounding. The resistance of the phase-zero loop consists of the total resistance of the phase and neutral wires, transition contacts in the line and the internal resistance of the power source. Will there be a zeroing, or will not it - the loop resistance from this will not change in any way. But the current of a single-phase short circuit depends on the resistance of this loop, the magnitude of which selects a circuit breaker in such a way as to provide in the case of a short circuit shutdown time required.

So, the neutralization of the cases of electrical appliances will lead to the fact that a short to the body will become a phase short to the neutral wire and (if the loop resistance is sufficient) to automatically turn off the damaged section of the network. If there is no grounding of the case, then the body of the appliance will remain energized and will be dangerous when touched. That is, the next mistake of the article is that in the absence of zeroing, there will be no current at all! Just the case will be energized.

Again erroneous statement. Yes, there was such a requirement in the EMP 6. Since 2000 (or 2002, too lazy to watch))) it has been canceled.

Instead, the concept of "TT grounding system" was introduced. It is used in accordance with the requirements of paragraph 1.7.59 in cases where safety in the TN system cannot be ensured. Security in the TN system is not ensured in several cases.Well, for example, a very long line and phase-zero loop resistance cannot provide fast automatic shutdown; a country house or a private house connected to an old-type overhead line with bare wires; metal trailer connected to the overhead line.

In these cases, automatic shutdown is organized using an RCD (for a current of 300 mA) installed at the entrance to the building and its own ground, NOT connected to the neutral wire (transformer neutral). The RCD has a high speed of operation, and the trip current is also very small and sufficient to trip when a short to ground occurs. Moreover, the resistance of the grounding loop can be quite large, i.e. there is no need to fence a design with 4 ohms (or 30 ohms).

And the last thing I would like to say:

In fact, of course it is. But in fact))) these are different things, with different purposes, with different principles of work. The main purpose of grounding is to reduce touch voltage. The main purpose of grounding is to create a single-phase short circuit and disconnect the damaged area. And the fact that in everyday life these concepts are often confused is for sure.

I apologize, with an attempt to quote the name GOST R 50571.3-94, an incident turned out, hence the garbage in the message.

Alex Gal, cleaned from garbage, for the expanded comment BIG THANKS!

Thanks to Alex Gal, for the first time I see such a competent and understandable explanation.

Thanks Alex Gal, you need to add to the EMP as an explanatory link "for especially gifted electricians"

Why make so much noise? If 3 wires (phase, zero and earth) come to your outlet (apartment), then safely connect a protected outlet using the icons on the contacts. If two wires (phase and zero) come into the socket (apartment), then first with a test screwdriver you determine which phase (the screwdriver is lit) and which zero (does not light) and after connecting the socket with an additional piece of insulated wire of the same cross section, shorten the zero terminal of the socket with a socket terminal with an earth icon. So you protect yourself from an open circuit in the connected device and phase in the case of this device. In another way, just pull a separate three-core line (phase, ground, zero) into the apartment (house). And do not contradict! If there is no such line, then do it just as I described - otherwise, if there is an open circuit in the device and there is no grounding - the device’s case will be “under phase” and the voltage will only wait when you touch the case and create a conductive circuit with this " phase-casing of the device-man-room-earth "and you will be shocked by the current. ! The machine will not turn off! But when the case is nullified, a short circuit will occur and, at least, the current through the nullified case will pass with less resistance than through you, the room, and so on. So, in this case, there will be an electric shock if it is slight (tingling) that will let you know that the device is not working and must be disconnected from the network. And even better and safer for such systems with two wires (phase and zero), install differential residual current circuit breakers (with a residual current of not more than 30 mA). In this case, it is not necessary to close the wires "zero" and "ground" in the socket (read it is impossible). Such machines even with the indicated tingling will disconnect your network. A mustache.

Neutral, like this, DO NOT DO IT FOR EVERYONE literally in every article, plus a few explain the consequences of such an initiative, so that only pulling three wires and not too lazy to make an intelligent separation of PEN (zero conductor) in the input shield.

Everything is right and true .... that's just the question .... a 5-storey building of an old building ... there is no ground wire ... you can’t write to the pipe, what can you do? .... and it is the apartment on the 5th floor ..

For Pavel, in your case, you still need to stretch the core for grounding, that is, connect the apartment to consumers in the apartment, and to the zero bus in the shield. In this case, even during breakdown, the phase current will be “behind the apartment”. But keep in mind that the electrical conductivity of the ground must be higher than the wiring (zero).

The article is certainly interesting, but there is one point that was missed both in the article and in the comments, protective grounding is used to protect electrical equipment, and protective grounding to protect against electric shock. And this is done only at industrial facilities. In household networks 220/380 it is strictly forbidden to do this because when a zero PEN conductor is burned out in the switchboard in front of the apartment or at the entrance to the house or in another place on the “EARTHED” devices, this way the phase potential will appear. So think you need such protection.

And for those who ask how to make grounding, for example, on the 5th floor, everything is enough just talk with your neighbors throw off money, find people to make normal grounding and talk a separate wire on the riser.

With grounding, everything is very simple. In electrical installations with dead-grounded neutral, it is necessary to provide automatic shutdown of the damaged area when shorting to the housing. The use of grounding in such electrical installations is impractical, since in order to reduce the voltage on the housing during a single-phase circuit to a safe value, grounding devices with low resistance would be required.

Short-term emergency mode allows you to ensure safety (by reducing the time the voltage affects a person) and the safety of electrical equipment. However, the operation of protective devices used in electrical installations (fuses, circuit breakers, etc.) occurs successfully only with significant currents in the circuit, therefore it is necessary to provide a path with a sufficiently high conductivity for the current in the circuit to the case, i.e. exclude current limitation by significant resistance of neutral grounding and equipment. This is achieved by the device of a metal connection between the electrical equipment housings and the neutral, which turns the circuit on the housing into a single-phase short circuit. This is grounding.