TN and its varieties
The most common type of grounding system is TN, in which zero is combined with the earth along its entire length. This type is also called in the supply a dummy neutral, when the conditional zero N of the source is connected to the PE grounding device. The grounding device is not difficult, but nevertheless it is technologically a group of pins driven vertically into the ground to a considerable depth to the aquifer, from 2.5 m or more. These pins are connected by a strip or cable into a single earthing loop of a residential house. Let's consider what classification of TN systems exists today and what is the difference between all varieties.
TN-C
In the old housing stock the type of protection TN-C is used, this is when zero N also acts as PE protective conductor, combined. This is the simplest and cheapest option for grounding an electrical installation up to 1000 V.
The TN-C type is obsolete and electrically dangerous, since it does not have a separate protective conductor, and in the event of an open circuit during an emergency, all potential will be on electrical equipment, exposing itelectric shock or fire.
TN-S
Therefore, in the newly designed buildings, another TN-S subsystem is used, in this device there is a separate wire phase, zero( neutral) and protective conductor PE. Conductors N and PE, starting from a substation with a solidly grounded neutral are separate components of the power supply system.
This type is the most reliable of the accepted types of grounding of the electric network. To its disadvantages can be attributed high cost, as it needs an additional conductor, from substation to consumer.
TN-C-S
Deprived of these drawbacks, the relatively simple TN-C-S system, which combines the advantages of the previously described systems. It is also easily realized during the reconstruction of old buildings. The meaning of this scheme is that the TN-C system is organized prior to the MSB, then a neutral PEN wire is divided into two conductors N and PE, then the TN-S system proceeds.
The disadvantage of this system is the same as for TN-C, when the PEN bus is disconnected the system is under full voltage. With this disadvantage, they are struggling with the installation of additional devices, such as voltage relays, which produce an emergency shutdown of the consumer from the network.
TT and IT
There are two other types of supply that are used in special conditions, this is the TT type - when the delivery of electrical energy is organized by phase conductors from a source with a deadly grounded neutral, and the grounding is organized directly at the consumer. In this way, mobile homes, temporary objects are connected. This type requires mandatory use of residual current circuit-breakers.
Another option is an IT system, a type of supply that does not use a deaf-earthed neutral. The source zero is connected through special devices having high internal resistance, and a zero and protective earthing device is directly installed at the consumer( according to the rules of the CEE 7, Chapter 1.7).This type of supply is used in special laboratories, since the interference introduced in this way is minimal.
We also recommend viewing the video, which provides a description of each type of grounding system with the following abbreviations:
And finally we want to draw your attention - it is forbidden to use heating pipes, gas pipes, water pipes, metal fencing elements as protective earthing. In this case, the appearance on these elements of a total voltage of 220 volts, exposing the life of the surrounding danger. Take care of yourself.
That's all I wanted to tell you about the main types of grounding systems used in Russia. We hope, now you know what are the circuits of ground loops and what are the differences between the existing options!
It will be interesting to read:
- Wiring diagram of voltage relay
- In the bathroom it is shocked - what to do
- How to make grounding in an apartment with your own hands
