Earthing means connecting of the non current carrying parts of an electrical device or equipment or the neutral point of the power system to the earth through a wire or conducting materials having very low resistance. Earthing is very necessary for equipment and power system. It protects the electrical equipment and power system against short circuit fault currents and lightning. In this article, we will deal with the objectives of earthing and types of earthing.
Objectives of Earthing
- It provides the safety to personnel against electric shock. It insures the safety of human beings during insulation failure.
- It protects the device or electrical equipment against damage which may cause due to the flow of overload current during short circuit conditions.
- It limits the over voltages from neutral to ground or line to ground.
- Earthing suppress dangerous earth potential gradients.
Types of Electrical Earthing
Earthing can be divided into two types
- Neutral Earthing
- Equipment Earthing
Neutral earthing deals with the earthing of the system neutral to ensure system security and protection. Neutral earthing is also known as system earthing. There are various methods for neutral earthing. The name of these methods is given below:-
- Isolated Earthing
- Resistance Earthing
- Reactance Earthing
- Solid Earthing
Equipment earthing deals with earthing of non-current carrying parts of the equipment to ensure safety of personnel and protection against lightning. Equipment earthing is also known as safety earthing. The name of different types of earthing is given below.
- Plate Earthing
- Pipe Earthing
How to earthing protect the personnel against electrical shocks?
In this example, we will explain about protection of personnel against electric shock.
In the first case, a man touches an electric motor. If a short circuit occurs in a motor the short circuit current starts flowing through a human body.
In the second case, an electrical machine is earthed. When a man touches the motor during short circuit conditions, the whole fault current flows through an earth wire instead of flowing through the human body.