What is TNS Earthing System?

In India, TNS (TN-S) earthing systems are commonly used in residential and commercial buildings and are required by electrical codes and standards. These systems are a safe and reliable choice for electrical installations in India, and are compatible with a wide range of electrical devices and appliances.

In addition to being widely used in India, TNS earthing systems are also commonly used in many other countries around the world. They are a popular choice for electrical installations due to their safety, reliability, compatibility, and cost-effectiveness.

Purpose of a TNS Earthing System

The main goal of a TNS (TN-S) earthing system is to ensure the safety of an electrical installation and protect people and property from electrical hazards. It achieves this by providing a low-resistance connection to the ground, which helps dissipate electrical current and prevent electrical shocks or fires.

In a TNS earthing system, the electrical supply connects to the ‘neutral’ conductor (N), and the earth conductor (S) connects to a metallic structure, such as a metal water pipe or metal rod, buried in the ground. The electrical installation connects to the ‘live’ conductor (T). If a fault occurs in the electrical installation (such as a short circuit), the fault current flows through the earth conductor to the ground, rather than through the electrical installation or the people using it. This helps prevent electrical shocks and damage to the electrical installation.

It is important to note that a TNS earthing system does not prevent a fault or short circuit from occurring, but it ensures that the fault current dissipates safely to the ground, protecting people and property from electrical hazards.

TNS Earthing System VS TN-C, TN-C-S, IT

Several different types of earthing systems are used in electrical installations, including TN-S, TN-C, TN-C-S, and IT. Each system has specific characteristics and suits different situations. It depends on the needs of the electrical installation and local electrical codes.

A TN-C earthing system is similar to a TN-S system. In this system, the earth conductor (C) also serves as the neutral conductor. The earth conductor connects both the neutral point of the electrical supply and a metallic structure buried in the ground.  Typically, smaller installations, such as single-phase residential dwellings, use TN-C systems.

A TN-C-S earthing system combines the TN-C and TN-S systems. In this case, the system uses the earth conductor (C) as the neutral conductor, and it also includes a separate earth conductor (S) that connects to a metallic structure buried in the ground. TN-C-S systems often serve larger installations, such as multi-phase commercial or industrial buildings.

An IT (isolated neutral) earthing system is used in systems with a high voltage level (greater than 1 kV). In an IT system, the system isolates the neutral conductor from the earth or any other metallic structure. The system connects the electrical installation to both the live conductor (T) and the neutral conductor (N). IT systems are typically used in power generation, transmission systems, and some industrial applications.

TNS earthing systems are generally less expensive to install and maintain than other types of earthing systems, such as IT systems. There are several reasons why TNS earthing systems may be less expensive to install and maintain.

1. Simplicity: TNS earthing systems are relatively simple and straightforward, with fewer components and a more straightforward installation process. This can make them less expensive to install and maintain than more complex systems.
2. Compatibility: TNS earthing systems are compatible with a wide range of electrical devices and appliances, including those with a neutral conductor. This means that they can be used in a variety of applications without the need for specialized equipment or materials.
3. Materials: TNS earthing systems typically use inexpensive materials, such as copper or aluminium conductors and metallic structures (such as metal rods or water pipes) for the earth connection. This can make them less expensive to install and maintain than systems that use more expensive materials.
4. Labour: TNS earthing systems are relatively easy to install and maintain, which can result in lower labour costs compared to other types of earthing systems.

It is important to note that the cost of installing and maintaining an earthing system depends on various factors. These factors include the size and complexity of the electrical installation, materials used, and labor required. TNS earthing systems may be less expensive to install and maintain than other types of earthing systems. However, this depends on the specific circumstances of each installation.

Designing a TNS Earthing System

There are several considerations that should be taken into account when designing a TNS (TN-S) earthing system for a particular location or type of building:

1. Local codes and standards: Adhere to local electrical codes and standards when designing a TNS earthing system. These codes specify the minimum requirements for earthing systems in the area. They include materials, size of the earth conductor, earthing electrode, and earthing resistance limits. For India, refer to IS 3043 (2018) – Code of Practice for Earthing and the National Building Code (2016)
2. Soil conditions: The soil conditions at the site impact the design of the TNS earthing system. For example, if the soil is highly resistive (such as dry, sandy soil), it may be necessary to use a larger earthing electrode. Special measures, such as using chemical earthing, may also be required to ensure that the earthing resistance is kept within acceptable limits.
3. Building materials: The materials used in the construction of the building affect the design of the TNS earthing system. For example, if the building is made of materials that are not conductive (such as concrete or brick), a larger earthing electrode with a larger surface area may be required. This ensures a low-resistance connection to the ground.
4. Size and complexity of the electrical installation: The size and complexity of the electrical installation impact the design of the TNS earthing system. Larger or more complex installations may require a more robust earthing system with a larger earth conductor and earthing electrode. They may also require additional protective devices, such as circuit breakers or fuses.

Components of a TNS Earthing System

The main components of a TNS (TN-S) earthing system include:

1. Earth conductor: This conductor (usually made of copper or aluminium) connects the electrical installation to the ground. In a TNS earthing system, the system connects the earth conductor (S) to a metallic structure (such as a metal water pipe or metal rod) buried in the ground.
2. Neutral conductor: This conductor (usually made of copper or aluminium) connects the electrical installation to the neutral point of the electrical supply. In a TNS earthing system, the system connects the neutral conductor (N) to the electrical supply.
3. Live conductor: This conductor (usually made of copper or aluminium) carries electrical current from the electrical supply to the electrical installation. In a TNS earthing system, the system connects the live conductor (T) to the electrical installation.
4. Earthing electrode: This metallic structure (such as a metal rod or water pipe) is buried in the ground to provide a low-resistance connection to the earth. In a TNS earthing system, the system connects the earth conductor (S) to the earthing electrode.
5. Protective devices: These devices (such as circuit breakers or fuses) protect the electrical installation from overcurrent or short circuit conditions.
6. Wiring: This conductor (usually made of copper or aluminium) connects the various components of the electrical installation.

TNS Earthing Installed in a Building/Structure

The installation of a TNS (TN-S) earthing system in a building or other structure typically involves the following steps:

1. Design: The first step in installing a TNS earthing system is designing the system according to relevant electrical codes and standards. Consider the size and complexity of the electrical installation, soil conditions at the site, and materials used in the building’s construction.
2. Installation of earthing electrode: The installation team uses a metallic structure (such as a metal rod or water pipe) as the earthing electrode. This provides a low-resistance connection to the ground. They dig a hole at the desired location and insert the electrode into the ground.
3. Connection of earth conductor: The installer uses a conductor (usually made of copper or aluminium) as the earth conductor to connect the electrical installation to the earthing electrode. They run the conductor from the electrical installation to the earthing electrode and connect it using a suitable connector.
4. Connection of neutral conductor: The installer uses a conductor (usually made of copper or aluminium) as the neutral conductor. It connects the electrical installation to the neutral point of the electrical supply. They run the conductor from the electrical installation to the main electrical panel and connect it to the neutral point of the electrical supply.
5. Connection of live conductor: The installer uses a conductor (usually made of copper or aluminium) as the live conductor to carry electrical current.

Potential Hazards associated with a TNS Earthing

1. Electrical shock: If the TNS earthing system does not function properly, users risk electrical shock. Various factors can cause this. Those include a damaged earth conductor, earthing electrode, or a failure of protective devices like circuit breakers or fuses. To reduce this risk, regularly inspect and maintain the TNS earthing system. Ensure it is properly designed and installed according to relevant electrical codes and standards.
2. Fire: If the TNS earthing system does not function properly, electrical fires may occur. This happens due to the accumulation of electrical current in the installation. To reduce this risk, regularly inspect and maintain the TNS earthing system. Ensure it is properly designed and installed according to relevant electrical codes and standards.
3. Corrosion: The materials in a TNS earthing system, such as copper or aluminum conductors and metallic structures, can corrode over time. Corrosion can affect the system’s performance and increase electrical hazards. To mitigate this risk, use corrosion-resistant materials when designing and installing the TNS earthing system. Regularly inspect and maintain the system to ensure it functions properly.

This is why it is critical to properly maintain any Earthing System that you implement for your structure.

Maintenance of Earthing System

There are several steps that you can take to properly maintain a TNS (TN-S) earthing system:

1. Perform regular inspections: Regularly inspect the components of your TNS earthing system. Ensure they are in good condition and function properly. Check the condition of the earth conductor, earthing electrode, and any protective devices, such as circuit breakers or fuses.
2. Test the earthing resistance: Periodically test the earthing resistance of the TNS earthing system. Ensure it remains within acceptable limits. Use an earthing resistance tester to perform this test.
3. Repair or replace damaged components: Repair or replace any damaged or malfunctioning components of the TNS earthing system. Do this as soon as possible to ensure the safety and reliability of the electrical installation.
4. Follow proper procedures when making changes to the electrical installation: Carry out any changes or modifications to the electrical installation only by a qualified electrician. Ensure they are done in accordance with relevant electrical codes and standards.
5. Follow proper procedures when using electrical appliances: Use electrical appliances in accordance with the manufacturer’s instructions. Unplug them when not in use.

How do I know if my property has a TNS Earthing System Installed?

There are several ways you can determine whether your property has a TNS (TN-S) earthing system installed:

1) Check the electrical panel: Locate the electrical panel in a central area of the building, such as a utility room or basement. The panel contains circuit breakers or fuses that protect the electrical installation from overcurrent or short circuit conditions. The panel also has a grounding terminal, which connects the earth conductor (S) to the earthing electrode. If your property has a TNS earthing system, you should be able to find the grounding terminal in the electrical panel.

2) Check the wiring: If you have access to the wiring in your property (for example, if you have exposed wiring in an unfinished basement or attic), identify the earth conductor (S), neutral conductor (N), and live conductor (T). In a TNS earthing system, the earth conductor (S) connects to the earthing electrode, the neutral conductor (N) connects to the electrical supply, and the live conductor (T) connects to the electrical installation.

3) Consult the property’s electrical plans: The electrical plans for your property should include information about the installed earthing system. You can usually obtain a copy of the electrical plans from the property’s previous owner or the local authorities.

4) Consult a qualified electrician: If you are unsure whether your property has a TNS earthing system installed or if you have concerns about the safety or reliability of the earthing system, consult a qualified electrician. The electrician can inspect the electrical installation, determine the type of earthing system installed, and identify any issues or deficiencies. They will also provide recommendations for repairs or upgrades to ensure the safety and reliability of the earthing system.

Conclusion

In conclusion, TNS earthing systems are a vital component of any electrical installation, and it is important to understand their role in ensuring the safety of people and property.

Axis can provide a range of services to help clients design and install a TNS earthing system, including:

1. Design and engineering services: Axis Electricals can provide expert design and engineering services. They help clients develop a customised TNS earthing system. This system meets the specific requirements and characteristics of their electrical installation. Services may include selecting appropriate materials, sizing earthing conductors, and selecting the most suitable earthing electrodes.
2. Hardware Supply: Axis Electricals supplies the hardware and materials needed for the TNS earthing system. This may include earthing electrodes, such as copper plates, rods, or pipes. They also supply earthing conductors, protective conductors, bonding conductors, and other components.
3. Installation services: Axis Electricals offers professional installation services. They help clients install their TNS earthing system. This may include installing earthing electrodes, connecting earthing conductors, and installing protective devices, such as circuit breakers or fuses.
4. Testing and verification services: Axis Electricals provides testing and verification services. These services ensure that the TNCS earthing system is correctly installed. They also ensure that it functions properly. This may include using specialized test equipment. The equipment measures the performance of the earthing system. It also helps identify any issues that need correction.

By providing both the hardware and the services needed to install the earthing system, Axis offers a complete solution to clients looking to design and install a TNS earthing system.