When installing electrical networks in premises for various purposes, protection must be provided to prevent possible electric shock to a person. And for this, grounding and zeroing are used. And not everyone knows what their difference is. After all, both of them ensure the safety of the use of electrical appliances.
По сути, эти два понятия во многом схожи, из-за чего их часто путают, но выполняют они свои функции по-разному. Поэтому постараемся разобраться, что в них общего и чем отличаются.
Grounding
Let’s start by looking at each system individually.
So, grounding is a deliberate connection of an electrical network, device or equipment with a special design, buried in the ground through a neutral conductor.
In fact, this is a single system that connects the conductive elements of instruments and equipment (for example, their cases), wires connected to them, and pins buried in the ground (circuit).
Due to the high resistance of the circuit when the phase wire touches the case in the event of a breakdown, most of the voltage goes to the ground, and although the potential will still remain on the case, its value will be significantly reduced and harmless to humans.
The international standard developed by the IEC includes several grounding systems, the differences between which come down to different types of grounding of the power source (generator or transformer substation), and grounding of open network sections, devices.
The standard includes three systems – TN, TT and IT.
The first letter of the index indicates the type of source grounding (T – “ground”, it turns out that in the first two systems the transformer substation is connected to the ground loop.
As for the third (IT), then its power source is insulated, or it is connected to a device that provides high resistance (I – isolation).
The second letter of the index indicates the type of grounding of open sections of the network. In the TN (N – neutral) system, these sections are connected to the neutral conductor of the source connected to the ground loop (deaf neutral ground).
To connect equipment and devices, working (N) and protective (PE) neutral conductors are used.
As for the other two systems – TT and IT, the second letter index indicates that open sections of the network, equipment and devices are grounded by their own separate circuit.
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In turn, the TN system is divided into subsystems, there are three of them – TN-C, TN-S, TN-CS.
The differences between them come down to the use of different protective conductors, with which consumers are connected to the source neutral.
The TN-C subsystem uses a combined conductor (PEN), which combines both the working and the protective “zero”. This subsystem is already obsolete, so it is not used when laying new electrical networks.
The TN-S subsystem is different in that it has a working and protective “zeros” – these are different conductors. That is, the N-conductor is connected to the neutral, and the PE-conductor is connected to the ground loop, even though they are combined on the power source.
Третья подсистема – TN-C-S является промежуточным звеном между первыми двумя подсистемами. У нее от нейтрали отходит PEN-проводник, то есть нулевые проводники объединены, но на определенном участке сети они разделяются и к потребителям подходит отдельно рабочий и защитный «нули». После разделения защитный «нуль» дополнительно заземляется.
Более подробно о системах заземления, их достоинствах и недостатках можно почитать здесь https://elektrikexpert.ru/sistemy-zazemlenij.html.
The requirements for grounding are quite serious. After all, it must ensure the removal of dangerous voltage from the device or equipment in the event of a breakdown.
Grounding is mandatory for networks in which the voltage is higher than 42 V AC or 110 V DC.
Therefore, when designing, parts of the network and equipment that are subject to mandatory grounding must be correctly selected, and control must be exercised so that the grounding circuit is not interrupted anywhere.
Seriously approach the choice of conductors, their cross section should provide the appropriate bandwidth.
Все требования, которые выдвигаются системам заземления прописаны в ПУЭ (Правила устройства электроустановок).
Here you can learn more about how to make grounding in a private house.
Zanulenie
And now for zeroing. The definition of this term indicates that zeroing is a deliberate connection of conductive, but not energized, elements of instruments and equipment with a dead-earthed neutral (three-phase transformers), a current source output (single-phase transformer), the midpoint of a source supplying direct current.
That is, the case of any device connected to the network must be additionally connected to the neutral of the power source.
For TT and IT systems, zeroing is not used, since a separate circuit is used to ground consumers.
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To create a zero, a zero protective conductor (PE) is used, which is connected to the source neutral.
But the PUE immediately explains that a working conductor (N) can also be used as a protective conductor, which implies that a PEN conductor can also be used to create a zero.
What is their difference?
It turns out that zeroing, in fact, is the same grounding made according to the TN system, but if we consider in more detail, then there is a difference between them.
The first is that when grounding, the combined neutral PEN conductor (TN-C and TN-CS systems) and the PE conductor (TN-S system) act as an intermediary between the devices and the transformer ground loop.
That is, there is a power source, near which the circuit is buried and together they are connected.
The wiring from the source goes to the consumer (room), where it branches out to provide power to all electrical appliances and equipment.
To ground these devices (provide protection), the same wiring is used, namely neutral conductors, and the transformer circuit.
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But when zeroing, the connection is made not with the circuit, but directly with the neutral conductor of the transformer.
А поскольку в обоих случаях используется один проводник — нулевой (в совмещенном – PEN-проводник, в разделенном – РЕ-проводник), то в конструктивном плане заземление и зануление – одно и то же.
Secondly, each of them works differently, although the design is the same.
In the case of grounding, when a dangerous potential appears in unclosed sections of the network, it will be discharged into the ground through a ground loop with high resistance.
Зануление же работает с точностью до наоборот. При соприкосновении фазы с корпусом, подключенным к нулевому проводнику, происходит резкое возрастание силы тока в следствие малого сопротивления, то есть происходит короткое замыкание, в результате которого срабатывают автоматические выключатели, устройства защитного отключения, либо же плавятся предохранители.
So it turns out that grounding and grounding are technically one and the same, but they provide protection in different ways.
In general, both of them are aimed at ensuring maximum protection of a person from possible electric shock during a phase breakdown to zero, and complement each other.
Features of creating grounding and grounding
Now about how everything looks in practice. When creating a TN-CS subsystem, a combined neutral conductor (PEN) is pulled from the transformer to the room.
In the input switchgear (ASU), it is divided into N and PE conductors. At the same time, three wires reach the end consumer – phase, working and protective zeros.
READ ON TOPIC: How to ground a washing machine.
When connecting the device, it turns out that by means of a PE conductor it is connected to a PEN conductor, which is both a connector with a ground loop and a solidly grounded neutral.
Approximately the same thing happens in the TN-S subsystem with the only difference that grounding and grounding is carried out by separated neutral conductors.
That is, in these two subsystems, creating grounding, zeroing is automatically performed.
But in the TN-C system, this does not happen. The fact is that it uses a PEN conductor, which does not split at the input.
It turns out that only two wires reach the end consumer – phase and working zero, and there is no protective PE conductor, in fact, the end consumer is not grounded.
Therefore, zeroing is created – the connection of consumer cases with a zero working conductor.
If in the above subsystems, creating grounding, zeroing immediately appears, then in this one it has to be created separately.
In this case, grounding is an alternative to grounding to provide at least some protection.
Therefore, TN-C is considered obsolete because it does not provide adequate security.
The question often arises – why is zeroing needed at all, because grounding is considered a safer system.
We simulate the situation: there was a breakdown of the phase on the body. Grounding provided the removal of most of the voltage to the ground, but some of it still remained on the case, while the current value will increase, albeit slightly.
This is not dangerous to humans, but can lead to unpleasant consequences. Since a strong current surge will not occur due to the lack of zeroing, the protective equipment simply will not work, and the damaged area will not turn off.
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As a result, damage to equipment or a section of the electrical network, a fire may occur.
It turns out that grounding and grounding complement each other, the first one disconnects the damaged section of the circuit, and the second one neutralizes the negative consequences of a short circuit in the network, providing the maximum possible protection against electric shock.
It is often stated that zeroing is not done in TN-S and TN-CS systems. And this is so, but only partially. After all, according to the above, when creating grounding, we immediately do zeroing. And only in TN-C zeroing is a separate type of work.
From here you can immediately judge where zeroing is used and where not. It is present wherever the TN system is used. But if in old buildings it had to be created separately, then in new buildings it is done during the installation of grounding.
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