Electricity is an essential part of our daily lives. From powering our homes to running industries, it has become an integral part of modern society. However, with the use of electricity comes the risk of electric shocks and equipment damage. This is where electrical earthing comes into play.
Definition: What is Electrical Earthing?
Electrical earthing, also known as grounding, is the process of connecting an electrical system or equipment to the ground. The purpose of earthing is to provide a safe path for electric current to flow in case of a fault or abnormal conditions. It helps prevent electric shocks and protects equipment from damage.
Types of Earthing Systems
There are several types of earthing systems used in the industry. Let’s take a closer look at each of them.
Solid earthing, also known as direct or pipe earthing, is the most commonly used type of earthing system. In this method, the neutral point of the electrical system is directly connected to a buried electrode in the ground. The electrode can be a copper rod, copper plate, or a galvanized iron pipe. The main advantage of solid earthing is its simplicity and low cost. However, in case of a fault, it can cause high magnitude short-circuit currents.
Resistance earthing involves the use of electrical resistance to limit the fault current flow through the ground electrode. This type of earthing uses a resistor in series with the earth connection. The resistor is usually made of graphite, coke breeze or a mixture of salt and charcoal. The main advantage of resistance earthing is that it limits the magnitude of fault current, reducing the risk of electrical fires. However, it requires regular maintenance to ensure the resistance value remains within acceptable limits.
Isolated Neutral Earthing
Isolated neutral earthing, also known as ungrounded or isolated grounding, is used in systems where continuity of service is vital. In this method, the system’s neutral point is not connected to the ground but is grounded through an impedance device such as a resistor or reactance coil. This type of earthing prevents overvoltages from occurring and protects against equipment damage.
Petersen Coil Earthing
Petersen coil earthing is a specialized type of earthing used for ungrounded or high-resistance grounded systems. It involves the use of a special coil, known as the Petersen coil, connected between the neutral and ground to provide earth fault protection. This technique reduces the risk of power outages due to earth faults.
Impedance earthing, also known as high-resistance grounding, is a combination of solid and resistance earthing. It uses a neutral grounding transformer with an impedance connected between the neutral and ground. In this method, the fault current is limited to a safe level while maintaining system continuity.
Safety Aspects of Electrical Earthing
One of the main reasons for having proper electrical earthing is to ensure safety. By connecting the system or equipment to the ground, it reduces the risk of electric shocks and protects against equipment damage. In case of a fault, the current flows through the ground instead of passing through a person or causing an explosion.
Earth Resistance Testing
Regular testing is essential to ensure that the earthing system is functioning properly. The earth resistance should be kept as low as possible to ensure the safe flow of fault current. There are different methods for testing earth resistance, such as using a megohmmeter or clamp-on tester.
Selecting the Right Earthing System
The choice of earthing system depends on various factors such as system voltage, type of equipment, and soil conditions. It is important to consider the trade-offs between different systems and seek expert guidance to ensure the most appropriate system is installed.
Electrical earthing is a crucial aspect of any electrical system, providing safety and protecting equipment. There are different types of earthing systems, each with its advantages and disadvantages. Proper testing and expert guidance should be sought when selecting the most suitable system for a particular application.