In this topic, you study Electrical Earthing – Definition, Working, Diagram & Purpose.
Earthing means to connect the bodies of electrical apparatus and equipment to earth with the help of a connecting wire (known as earth wire) of negligible resistance is known as earthing. The other name for earthing is grounding.
Purpose of Earthing
The basic purpose of earthing to avoid the dangers due to electric shock and fire, it is essential to have good and effective earthing. In an electrical installation if a metal part of an electric appliance equipment etc. comes in direct contact with a live wire, the metal, being a good conductor of electricity, will become electrically alive at the same potential as the live wire. If a human being comes in contact with the live metal part, he will experience a shock. It is, therefore, necessary, from a safety point of view, that an easier path is provided for the flow of current from the live metal part to earth so that the operator’s life is not endangered. This is done by connecting the body of electrical appliance to earth by means of a wire of very low resistance so that in case the body of the electrical appliance becomes alive, the current flows direct to earth through low resistance earth wire rather than flowing through the body of the human being which has higher resistance. Since the value of current through the earth wire shall be high, the fuse, circuit breaker or a protective device installed will operate to cut off the supply to the fault. So earthing of an installation is provided to make the operation safe.
As shown in Figure 1, consider the winding insulation of the motor faulty. And a human being comes in contact with the live metal part, experience a shock.
