Main types of earthing system?

1. TN-S system: In this system, the neutral and protective earth conductors are separate throughout the installation.

2. TN-C system: In this system, the neutral and protective earth conductors are combined up to a certain point, after which they are separated.

3. TN-C-S system: This system is a combination of TN-C and TN-S systems, where the neutral and protective earth conductors are combined at some points and separate at others.

4. TT system: In this system, the earth electrode is connected to the electrical installation at the point of supply, and each individual electrical device is connected to the earth electrode via its own earth connection.

5. IT system: In this system, the neutral point of the electrical installation is not connected to earth, and the earth electrode is connected to the electrical installation at a separate point.

6. PME system: This system is a variant of the TN-C-S system, where the neutral and protective earth conductors are combined at the point of supply and then separated within the installation.