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 an electrical machines and power system. It protects an electrical equipment and power system against short circuit fault current and lightning. In this article, we will deal with the objectives of earthing and the type of earthing.
Objectives of Earthing
- It provides the safety of the 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 a short circuit.
- It limits the over voltages from neutral to ground or line to ground.
- Earthing suppress dangerous earth potential gradients.
Types of Electrical Earthing
- 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
- Ripe Earthing
How earthing protects 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 electrical 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 touch with a motor. If a short circuit occurs in motor the fault current flows through an earth wire instead of flowing through the human body.