There are several types of earthing systems used in electrical installations to provide a safe path for fault currents to flow into the ground. The choice of earthing system depends on factors such as the local regulations, the type of electrical installation, and the level of fault protection required. Here are some common types of earthing systems:

1. TN-S System (Separated Neutral and Protective Earth):

   • In a TN-S system, the neutral conductor (N) and the protective earth conductor (PE) are separate throughout the entire electrical installation.
   • The neutral conductor is connected to the earth at the transformer or generator, while the protective earth conductor is connected to the earth at multiple points along the installation, typically at each socket outlet or equipment.
   • This system provides a low-impedance path for fault currents and ensures that the earth connection remains independent of the neutral conductor.

2. TN-C System (Combined Neutral and Protective Earth):

   • In a TN-C system, the neutral conductor (N) and the protective earth conductor (PE) are combined into a single conductor, known as the combined neutral and earth (CNE) conductor or PEN conductor.
   • The PEN conductor is connected to the earth at the transformer or generator, and it serves as both the neutral and protective earth conductor throughout the installation.
   • This system simplifies the wiring but requires careful monitoring and maintenance to ensure the integrity of the PEN conductor and to prevent dangerous conditions such as loss of the neutral connection.

3. TT System (Separate Earth and Neutral):

   • In a TT system, each electrical installation is individually earthed with its own earth electrode, such as a metal rod driven into the ground.
   • The neutral conductor (N) and the protective earth conductor (PE) are separate throughout the installation.
   • This system provides a high level of safety and reliability, especially in areas where the quality of the earth connection may vary.

4. IT System (Isolated or Impedance Earthed System):

   • In an IT system, the neutral point of the electrical system is not connected to earth, or it is connected through a high impedance.
   • Fault currents are limited by impedance, and the system relies on insulation monitoring and fault detection to ensure safety.
   • IT systems are commonly used in critical installations where continuous operation is essential, such as data centers, hospitals, and industrial plants.

5. Solid or Pipe Electrode Earthing:

   • This involves driving metal rods or pipes into the ground to provide a low-resistance path for fault currents.
   • Solid or pipe electrodes are typically made of materials such as copper or galvanized steel and are buried at a depth sufficient to ensure good electrical contact with the soil.

These are the main types of earthing systems used in electrical installations. Each system has its advantages and limitations, and the appropriate choice depends on factors such as the specific application, local regulations, and the desired level of safety and reliability.