Earthing



When we bring a charged body in contact with the earth, all the excess charge on the body disappears by causing a momentary current to pass to the ground through the connecting conductor (such as our body). This process of sharing the charges with the earth is called grounding or earthing.

Earthing is an important component of electrical systems because of the following reasons:

Earthing provides a safety measure for electrical circuits and appliances. A thick metal plate is buried deep in the earth and thick wires are drawn from this plate. These are used in buildings for the purpose of earthing near the mains supply.

The electric wiring in our houses has three wires: live, neutral and earth. The first two carry electric current from the power station and the third is earthed by connecting it to the buried metal plate. Metallic bodies of the electric appliances such as electric iron, refrigerator, TV are connected to the earth wire. When any fault occurs or live wire touches the metallic body, the charge flows to the earth without damaging the appliance and without causing any injury to the humans; this would have otherwise been unavoidable since the human body is a conductor of electricity.

 

Types of Earthing

LOCAL EARTHING

Local earthing is made near the energy meter in a house. A copper rod is connected to a copper plate which is buried inside the ground. Whenever the current in the circuit exceeds a value, it is sent to the ground with the help of the earthing wire.

 


EARTHING AN APPLIANCE

 

It is essential to provide an earthing connection to an electrical appliance. When a faulty wire comes in contact with the metal body of the appliance, it acquires a high potential and can cause severe shocks. These are prevented by earthing the appliance which drives the potential to zero.