Types of Electrical Insulators | Overhead Line Insulators

Generally 3 types of electrical insulators are used as overhead insulator. But i will discuss here about of 4 types of electrical insulators they are-:

  1. Pin Types Insulators

  2. Suspension Types Insulators

  3. Strain Types Insulators

  4. Post Types Insulators

Here neglecting the shackle & Stay type insulators, because they are used mainly for low voltage(400/230 V) application.


Pin Types Insulators

png Pin Type Insulators

A pin type insulator is small, simple in construction and cheap & it is earlier developed overhead line insulator. Pin type insulator is used on lines upto and including 33kV lines. It has bound into a groove on the upper end for keeping the conductor. Single or multiple pin insulators are placed on the cross arm of the physical supporting tower. This type of insulator is made of cemented on to a galvanized steel pin attached to the crossarm on the pole or tower. However, the number of insulators used depends upon the application’s voltage.


Suspension Types Insulators

Suspension Types Insulators

Suspension type of insulator are used in higher voltage, when line above 33kV. They are also known as disc type insulator or string insulators because of their disc like shape. The cost of a pin insulators increases proportionally with increase in line voltage. 

Rated Voltage(kV) Number of disc insulator used in suspension type insulators string
33KV 3
66KV 4-5
132KV 9-10
220KV 15-16
 400Kv 22-23

Strain Types Insulator

Strain Types Insulators

Strain insulator are special mechanically strong, that is designed to work in mechanical tension, to withstand the pull of a suspended electrical wire or cable. The disc of a strain insulator are in a vertical plane as compared to the disc of suspension insulator which are in a horrizontal plane. 

Rated Voltage(kV) Number of disc insulator used in Strain type insulator string
33KV 3
66KV 4
132KV 8
220KV 14

Post Types Insulators

post Types Insulators

These type of insulators usually used for supporting the bus bars ,& disconnecting switches in the sub-station. These insulators are constructed in the form of a cylinder. In extra high voltage sub-station like that 400kV & above , in this purpose polycon post insulators are used. These insulators exhibit high resistance to puncture proof, solid core insulator for outdoor use. 

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