The main types of earthing systems

By Admin | Electrical Light
20 April 2016

We have already written about grounding: what is it and how to do it, on the rules of grounding and advice on home ground.Member Forum "Home and cottageĀ» _KM_ offers available with varieties of grounding and the peculiarities of their use.

TN-C

for this old system grounding Soviet era characterized by the following: to the earth electrode, which is located in the substation, neutral wire is attached, also acts as a protective (PEN).Because of this protection, constructed in accordance with this scheme, often called "zeroing".This wiring makes the two a four-wire, grounding contacts in the sockets do not.

The main advantage of the system TN-C is the simplicity and low cost.The main drawback - the best of electric shock: protective device protects the network against overcurrent short-circuit, but not the people.

inclusion of modern electrical engineering from the switching power supply in the outlet from the TN-C leads to the phenomenon of removal of stress on the body.The reason for this are

switching power supplies that are at the entrance of a symmetrical filter pulse interference with the mid-point attached to the body.When voltage of 220V devices Vanishing divided on the shoulders of the filter and the housing is 110V.

In rural areas, in the absence of repeated groundings possible burning-off of the zero output of the supply transformer.Depending on the connected load, the voltage on the three phases of the unpredictable way warps, which leads to a failure of electrical household appliances.

Today earthing system TN-C is not used in the construction of new homes or reconstruction of old ones.

In older buildings, we recommend to move from a system of TN-C to TN-CS, ieto enter the building to make a re-grounding neutral conductor followed by separation of the wires on the PEN N (work zero) and PE (protective).To do this, you must make a separate center ground and replace all electrical wiring in the house.If for some reason this can not be done, it should at least provide a vanishing electrical devices.Grounding screws and stationary electrical terminals must be attached to the neutral wire.For portable devices are three-pole socket outlets, which are also attached to the neutral wire.

must be remembered that without these measures in the wiring to the system TN-C is considered safe to use only electrical appliances with double insulation and housing parts conductive.

TN-S

In this modern system of grounding conductors and the PE working neutral N are laid separately over the entire length with three-five conductor wires and cables.The use of such a system to prevent electric shock (differential used machines and protective devices).In addition, the wiring on the TN-S can be used without any risk of electrical consumers with metal casing.

Among the shortcomings of the system can call for the higher costs: necessary wires and cables with additional living and a separate center ground.Note that protect people against electric shock is possible, only using protective devices are not cheap and Emergency circuit breakers.When using the TN-S needs a qualitative and tidy wiring.

The main drawback of the system - the inability to fully use this system because of the fact that the 0.4 kV distribution network in Russia made four- lines.

eliminate this contradiction allows us to combine the grounding system.

TN-CS

Under this system, the protective conductor ground zero and working up to the building entry combined (PEN), to make re-entering the ground, after which they are divided intoPE and N.

System TN-CS is recommended for newly constructed and renovated facilities and buildings.

should be remembered that modern electrical devices intended for connection to networks with TN-CS (TN-S) and did not initially neutral earthing, ietheir metal casings and parts are not connected with supply conductors.Therefore such devices can be connected to the network only three-five-wire cables and wires with a compound of the ground terminal (bolt contact) to the ground terminal in the plug to ensure proper grounding of the automatic device.

It is interesting that many of the old domestic devices characterized by a rigid connection housing with zero.When connecting these devices to the network TN-CS (TN-S) may disable security leakage current.

When using TN-CS system is necessary to secure the re-grounding, also grounded all conductive parts and the building structure.

this purpose to enter the building satisfied the so-called main grounding bus, ieterminals.It is connected to the ground again and the house attached to it unbreakable metal conductors and design elements: reinforcing cage, pipes, metal bars, profiles, etc.

Advantages and disadvantages of TN-CS - the same as in TN-S.

TT

This earthing system is different from previous ones in that each electrical device must be individually grounded conductive housing.This ground zero on the transformer may not be as of the zero (previously common winding connection scheme "triangle", is now used in high-voltage distribution networks).

TT is not commonly used in electrical installations of residential buildings.The circuit may be of interest to the individual developers in the event that there is no proper center ground to enter the building and the need to organize its electrical power from, say, gasoline generator.

However, it should be remembered that, in addition to the frame of the generator to earth ground is necessary to connect one of the output contacts - when using a single-phase generator, the output midpoint - for three-phase.

system IT rarely used.As a rule - in electrical installations and special buildings, which are increased requirements for safety and reliability (for example, in hospitals for emergency lighting and power supply).

on materials forum participant "Home and Cottage"

Editor: Olga Travin