EARTHING SYSTEM AND ITS TYPES


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                  EARTHING SYSTEM AND ITS TYPES

Earthing is the process by which transmitting the immediate discharge of electricity by the help of low resistive wires to the ground. This is called the electrical earthing and is done by connecting non-current carrying part of the conductor to the ground.

System earthing must need to understand the potential of the conductor and it should be provided with the desired value for which the insulation is provided

THREE TYPES OF EARTHING SYSTEM

TT SYSTEM

The LV transformer’s neutral point is directly connected to an earth electrode and then the exposed conductive parts of the installation are connected to an electrically separated earth electrode

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RCD’s are used to reduce the fault currents, the fault current is too weak to trigger the short-circuit protection devices and by this fire protection is created

FEATURES OF TT SYSTEM

  • Fault current limited
  • First fault tripping
  • Human protection
  • Risk of fire is removed
  • Service continuity and simple design
  • Use of RCD’s

TN SYSTEM

In this, the neutral point of the transformer is connected to the earth electrode and the exposed conductive parts of the installation are connected to the same earth electrode by the protective earth conductors

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According to the arrangement of the neutral and protective earth conductors, the TN system is classified into three types

TN-S: the protective earth conductor is separated from neutral conductor

TN-C: the protective earth and the neutral conductors are connected by using a common conductor

TN-C-S: in this, the neutral and protective functions are combined in a single conductor in a part of the system

  • High fault currents
  • Dangerous touch voltage
  • Tripping after the first fault
  • Cost savings
  • Check on tripping conditions

IT SYSTEM

In this the neutral point of the LV transformer is isolated it is not connected to an earth electrode and the exposed conductive part of the loads are connected by the Protective earth conductor to a common earth electrode

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  • Protection of persons
  • Insulation fault is not dangerous
  • Continuity of service
  • First-fault current is very weak
  • First-fault touch voltage is very weak
  • Tripping after the second fault
  • Use of IMD for tracking faults