Types of Insulator - Pin, Strain, Disc, Shackle, Suspension

Hey, in this article we are going to learn about the main important types of insulators used in overhead electrical transmission lines. The main function of an insulator is to provide electrical isolation between a current conductive part and a non-conductive path by providing very high resistance to the flow of electric current. These insulators are mainly used in overhead lines to support the conductors and to prevent the flow of current from the conductor to pole or earth.

The most usable important types of insulator are,

• Pin Type Insulator
• Disc Type Insulator
• Suspension Type Insulator
• Strain Type Insulator
• Shackle Insulator
• Stay Insulator

Pin Type Insulator

Application Voltage Range: Up to 33KV

Pin type insulator is the most common and old insulator but till the day it used very much. It is the most simple type of insulator. It is mostly used in domestic power distribution and low voltage transmission lines. The single RCC Electric Pole uses the pin insulator. Pin type insulator is mostly used in 11KV lines but somewhere it is used up to 33KV lines. It may be used in one part or multiple parts. For example, in an 11KV system, if one part is used then in a 33KV system three parts are connected together. So the voltage capacity of a single pin insulator is 11KV. This type of insulator has more mechanical strength than other types of insulators. It can be constructed easily and can be placed in both horizontal and verticle positions.

Disc Type Insulator

Application Voltage Range: 11KV

This type of insulator is also used in both transmission lines and distribution lines. This is made of high-grade raw material. The main advantage of the Disc insulator is its lightweight. It is mostly used in low and medium polluted areas. It is corrosion protective also. Generally, a single disc type insulator is rarely used, it is used with multiple quantities by forming strain or suspension type insulator.

Suspension Type Insulator

Application Voltage Range: Beyond 33KV

Suspension means hanging. It is a combination of multiple disc insulators connected in series to form a string. Each insulator is made of a disc insulator. We can say multiple disc insulators are connected together to make the suspension type insulator. Each disc can carry the voltage 11KV(up to 15KV also). So, in a 33KV system, three discs are used. So the number of discs connected in a suspension string depends upon the voltage rating. It is mostly used in high voltage transmission lines where the pin-type insulator and other low-quality insulators can not be used. The suspension insulator is generally placed vertically. In high voltage electric poles, you can see its applications.

Strain Insulator

Application Voltage Range: Beyond 33KV

In the corner of the transmission line, the strain insulator comes in the use. The strain insulators are also built with multiple numbers of disc insulators but they are placed horizontally. At the corner of the transmission line, where a line end and a new line started, there two strain insulators are used. Strain insulator also used beyond the 33KV lines. For, 33KV lines three-disc insulators are used in both strain and suspension type insulators but above the 33KV such as 66KV, 132KV, the strain insulator has one extra disc insulator than the Strain insulator.

Shackle Insulator

Application Voltage Range: 230V, 440V

Shackle insulators are mostly used in low voltage distribution lines such as domestic electric poles, 440V lines, 230V lines, etc. These are the smallest size insulators. it is most suitable for line bend areas. Shackle insulators are placed in both horizontal and verticle positions.

Stay Insulator

Application Voltage Range: 230V

This type of insulator is not used to directly provide insulation between the live conductors and non-conductive parts. They are used in supporting lines of the electric poles. You can see the 230V electric poles are supported by a metallic wire or conductor and an insulator is connected in the middle of the wire. It is a rectangular-shaped device. Basically, it acts as a safety device to protect if accidentally the supporting wire is connected to the live conductor.

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