What are the 5 IEC types of earthing systems?

In electrical engineering, proper earthing is crucial to ensure the safety and stability of electrical installations. The International Electrotechnical Commission (IEC) has established a set of standards for earthing systems. This article aims to explain the 5 different types of earthing systems defined by the IEC in a simple and easy-to-understand manner.

Type 1 - TN-S System

The TN-S system, also known as separated neutral and protective earth, is one of the most common earthing systems utilized worldwide. In this type, both the neutral conductor and the protective earth conductor are separated throughout the entire electrical installation. The power source provides a direct connection to earth through the protective earth conductor, ensuring a high level of safety.

Type 2 - TN-C-S System

The TN-C-S system, also called combined neutral and protective earth, integrates the neutral and protective earth up to a certain point. In this system, the supply network has a combined PEN conductor (Protective, Earth, and Neutral) that is split into separate protective earth and neutral conductors after a specific point. This allows for efficient distribution of earth fault currents and reduces the risk of electric shock.

Type 3 - TT System

The TT system, or separately derived system, relies on an independent power source, such as a generator or transformer. In this system, the neutral point of the power source is earthed, while the exposed conductive parts have their individual earthing connections. The TT system offers good reliability and is often used in situations where the earth fault loop impedance is expected to be high.

Type 4 - IT System

The IT system, or isolated system, is commonly employed in sensitive environments where uninterrupted power supply is crucial. In this system, all equipment and structures are electrically isolated from earth, except for a single point called the reference earth point. The IT system provides high reliability and reduces the risk of electric shock by limiting current flow in case of a fault.

In conclusion, the IEC defines 5 distinct types of earthing systems: TN-S, TN-C-S, TT, and IT. Each system has its own advantages and purposes, ensuring a safe and reliable operation of electrical installations. By understanding these different types of earthing systems, electrical engineers can choose the most suitable one for specific applications, ensuring the safety and efficiency of electrical systems.