Electrical insulator is mainly used in electrical system to prevent or protect from unwanted or over flow of current in the transmission or distribution line or electrical circuit to the earth from its supporting point which is connected to the earth.
The insulator plays a vital role in electrical system or power system. Electrical Insulator is a very high resistive path through which no current can flow. In transmission and distribution system, the overhead conductor are generally use as a supported device by supporting tower or poles and it also insulate the poles or tower body from the line electricity. The poles and tower both are grounded to earth so there must be a insulation between the line and ground other wise the line current will directly grounded through the poles or tower body.
The main cause of failure of overhead line insulator are flash over which is occur in between line and earth during abnormal over voltage.
Due to this flash over in the line and earth, the huge heat produce by arcing which cause puncher in insulator body. So, prevent this phenomenon the materials used for electrical insulator, has to posses some specific properties.
Properties of Insulating Material
For the insulating purpose a specific kind of materials generally used which is called insulating material. This insulating material have some specific propertices which are-
- It must be mechanically strong enough to carry tension and weight of conductor.
- It must have very high dielectric strength to withstand the voltage stressed in high voltage system.
- In must possesses high insulation resistance to prevent leakage current to earth.
- The insulating material must be free from unwanted impurities and it should not be porous.
- There must not be any entrance on the surface of electrical insulation. So that the moisture or gases can enter in it.
- There physical as well as well as electrical properties must be less effected by changing temperature.
For the material the insulator are three the type-
- Porcelain Insulator
- Glass Insulator
- Polymer Insulator
For the shape and structure the insulator three are-