Overhead Line Insulations/ Insulators

There are Three types of insulators used for over head lines:

1. Pin Type

2. Suspention Type
3. Strain Type

1.Pin Type Insulator:- Pin Type insulator consists of a single or multiple shells (petticoats or rain sheds) adopted to be mounted on a spindle to be fixed to the cross arm of the supporting structure. Multiple shells are provided in order to obtain sufficiant length of leakage path so that the flash over voltage between power conductor and the pin of the insulator is increased.

Fig- Pin Type Insulator

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2.Suspention Type Insulator:- Suspention insulators being free to swing,the cearanance required between the power conductor and the supporting structure are more as compared to pin type insulators.This means that the length of the cross arm for suspension insulators is more as compared with the pin type.The suspention insulators is more as compared to pin type for voltage more than 33kV.

Fig- Practical Picture

Fig- Structure Of Suspension Insulator

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3.The Strain Insulators:- The Strain Insulators Are exactly identicalin shape with the suspention insulators. These Strings are placed in the horizontal plane rather than the vertical plane as is done in case of suspention insulators.These are Used to take the tension of the conductors at line terminals, at angle tower, at road crossing and at junction of overhead lines with cable.These insulators are,there fore,known as tension or strain insulators. For Low Voltage of the order of 11kV,shackle insulators are used. But for Higher Voltages a String of Insulator is Used.