Types Of Insulators In Transmission Lines

The main types of insulators in transmission lines are Pin type,Suspension type, Strain type and Shackle insulator. These are the types of insulator used in overhead lines.

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Types of Insulators used in Transmission lines

There common types of overhead line insulators used are;

Pin type Insulator
Suspension type Insulator
Strain type Insulator
Shackle insulator

Pin type Insulator

Pin type insulators are used for transmission and distribution of electric power at voltages
up to 33 kV.

Pin type insulator is fixed to the cross-arm on the pole and the conductor is housed
in a groove at the upper end of the insulator.

The conductor sits in the groove of this insulator and it is clamped with the assistance of an annealed wire of the same material as the conductor.

Suspension type Insulator

Suspension type insulators are used for voltages higher than > 33 kV.

A suspension type insulator consists of a number of porcelain discs connected in series by metal links in the form of a string.

The conductor is suspended at the bottom end of this string and the other end of the string is
fixed to the cross-arm of the tower.

Strain type Insulator

Strain type insulators are used when there is a dead end of the line or there is corner or sharp curve, under the influence of which the line is subjected to excessive tension.

Strain insulators help relieve this tension in high voltage transmission lines.

It consists of an assembly of suspension insulators in which the discs are used in the vertical
plane.

In case of long transmission lines, such as those over the width of the river, two or more insulators can be used in parallel.

For low voltage lines (< 11 kV), shackle insulators are used as strain insulators.