Understanding different types of earthing systems.

The TT earthing system is one of the three main types of earthing systems used worldwide, particularly in domestic electrical installations.

In a TT system, the first ‘T’ stands for the direct connection of one point in the power supply to the earth (usually the neutral point in a distribution network), and the second ‘T’ stands for the earth electrode independently installed at the consumer’s premises.

This means that there is no reliance on the utility’s earth connection, and each consumer has their own earth electrode, providing an independent path for fault currents to flow directly to the ground.

The TN-C earthing system is a type of earthing system where the functions of both neutral and protective earth are combined in a single conductor throughout the distribution system.

This is known as a combined PEN conductor. In this system, the ‘T’ stands for the direct connection of one point in the power supply to earth (usually the neutral point), and ‘N-C’ stands for Neutral and Combined (protective and neutral functions).

It’s important to note that in this system, there is no separate protective earth (PE) conductor, which can lead to certain safety risks if not properly managed.

The TN-S earthing system is a type of earthing system where the neutral and protective earth functions are separated.

In this system, ‘T’ stands for the direct connection of one point in the power supply to earth (usually the neutral point), and ‘N-S’ stands for Neutral and Separate (protective and neutral functions).

This means that there are separate conductors for neutral and protective earth throughout the distribution system, providing a clear and distinct path for fault currents to return to the source and enhancing safety by reducing the risk of electric shock.

The TN-C-S earthing system is a type of earthing system that combines aspects of both TN-C and TN-S systems.

In this system, ‘T’ stands for the direct connection of one point in the power supply to earth (usually the neutral point), ‘N’ stands for Neutral, ‘C’ stands for Combined (protective and neutral functions), and ‘S’ stands for Separate (protective and neutral functions).

The system starts as a combined PEN conductor from the source and then separates into individual PE (protective earth) and N (neutral) conductors before entering the premises.

This allows for the benefits of both systems: the economy of a combined neutral and earth conductor with the safety of separate conductors within the installation.

The IT earthing system is a type of earthing system where the electrical installation is isolated from the earth or one point is earthed through a high impedance.

In this system, ‘I’ stands for Isolation (or Impedance) from Earth, and ‘T’ stands for Terra (earth).

This system is often used in applications where power continuity is critical and where the first fault does not lead to a disconnection of the power supply.

It provides a high level of safety against electric shocks, as there is no direct connection to the earth that would allow fault currents to flow, thus reducing the risk of electric shock.