Choosing the right earthing system

Choosing the right earthing system for your power supply is crucial to protecting both people and property. And to make the right choice, you must understand how the different earthing systems affect electromagnetic compatibility.

What is an electrical earthing system?

An electrical earthing system is a critical part of any electrical installation, defining how the neutral point of a power supply, typically a transformer, is connected to the ground. The main function of an earthing system is to safeguard people and property from electrical faults while providing a stable reference for the electrical source. By doing so, it ensures that excess electrical energy, such as from a fault or lightning strike, is safely directed into the earth rather than causing harm.

Electrical earthing systems were designed decades ago to ensure safety and reliability, and they remain essential in today’s electrical installations. Beyond safety, the choice of an earthing system also affects the electromagnetic behavior of the installation. Different types of earthing systems can influence how electromagnetic disturbances, overvoltages, or transient currents travel through the electrical network. Improper selection of an earthing system can lead to unwanted noise, interference with sensitive equipment, or even damage to electrical devices.

Therefore, understanding the types of earthing systems and their implications is essential when designing an electrical installation. A well-planned electrical earthing system ensures not only safety and compliance with standards but also optimal performance and minimal electromagnetic interference across the network.

The four earthing systems

There are four main types of earthing systems: TT, IT, TN-C, and TN-S. Each has a specific setup suited to different applications.

• TT earthing system: In this system, the protective earth (PE) of the installation is independent of the utility’s earth. The consumer installs their own grounding electrode, which is not connected to the supply neutral. This earthing system is commonly used in rural areas or where a reliable utility earth is not available. It provides good protection against electric shocks but requires sensitive residual current devices (RCDs) for effective fault protection.
• IT earthing system: In IT systems, the supply neutral is either isolated from earth or connected through a high impedance, while the installation itself is earthed separately. This restricts fault currents during a single line-to-earth fault, helping lower the risk of electric shock and protecting equipment from damage. IT systems are often used in hospitals, industrial plants, and critical installations that require continuous power supply.
• TN-C earthing system: In TN-C systems, the neutral and protective earth conductors are combined into a single conductor called PEN. This electrical earthing system simplifies wiring but carries higher risk if the PEN conductor fails, as exposed parts could become live.
• TN-S earthing system: In this configuration, the neutral and protective earth are separate throughout the system. TN-S provides higher safety and reliability by preventing current flow through the protective earth, which reduces fault risks and electromagnetic interference.

Comparison of earthing system types

The main characteristics of the four earthing systems

In modern electrical installations, selecting the right earthing system is critical to ensure safety, reliability, and optimal performance. Among the available options, the TN-S earthing system is highly recommended by EU and international standards. Its design separates the neutral and protective earth conductors, which provides a stable reference point for the electrical source and minimizes risks associated with electrical faults. This electrical earthing system is particularly suitable for environments that include IT networks and communication systems, where electromagnetic disturbances can disrupt sensitive equipment.

• The TN-S earthing system offers a low-resistance path for fault currents, ensuring both personnel and equipment remain protected during electrical faults.
• By keeping neutral and protective conductors separate, this electrical earthing system reduces the risk of stray currents, improving system stability and reliability.
• Electromagnetic compatibility (EMC) is significantly enhanced with a TN-S earthing system, which is essential in installations with IT networks, data centers, and communication infrastructure.
• The independent conductors simplify fault detection and maintenance. Faults can be detected and resolved promptly without disrupting the rest of the system.
• International standards emphasize selecting an electrical earthing system that supports safety as well as EMC performance. TN-S consistently meets these criteria, providing a stable reference potential and limiting interference in sensitive equipment.
• Adopting this earthing system ensures uninterrupted operation of IT and communication networks while maintaining the overall reliability of electrical installations.

The TN-S electrical earthing system protects people and property, improves electromagnetic compatibility, and enhances the safe operation of modern electrical networks. Its compliance with global standards makes it the preferred choice for installations where safety, reliability, and system integrity are priorities.

Tips

• The earthing system should be chosen at the beginning of the installation design process.
• Neutral must be connected to earth at a single point as close to the transformer as possible.
• IT, TT, and TN-C earthing systems are often the source of disturbances; a separation transformer should be used in these cases.
• If the earthing system is not known, use a dedicated transformer to supply sensitive equipment (automation devices, electronics, interfaces, etc.).
• Use separate transformers to supply sensitive systems or systems that create disturbances.
• Use EMC filters (of the right size and correctly implemented).
• Use overvoltage protectors (of the right size and correctly implemented).
• Pay special attention to leakage current generated by EMC filter (phase and neutral to earth capacitors).

Tags: Electrical Installations, electrical panels, Electrocution, electromagnetic compatibility