Types of Insulators Used in Transmission Lines | Insulators Applications

What Is An Insulator?

In this article explain about What is an Insulator?, Types of Insulators, where can we use the insulator and their applications we will discuss in this article. an insulator is non conducting material which does not flow electrical current through this material called an insulator. Some examples of insulating material are paper, glass, plastic and air and also vacuum is an insulator, but it is not physical material. Insulators are generally rated at hundreds of volts, but in-case of power distribution systems are rated as high as hundreds of thousands of volts. Most electrical conductors are covered by insulation which are transformer winding wire is coated with extremely thin layer of insulation for more turns. Insulators in all applications mainly used for support and keep electrical conductors from making accidental contact each other.

Types of Insulators Used in Transmission Lines

The insulators are broadly classified into different types and rating based on their purpose. These insulators used in both transmission and distribution system so each insulator having several insulating discs. For example one disc used for 11kv voltage.

There are several types of insulators used in transmission lines for overhead insulation they are,

  • Pin Insulator
  • Suspension Insulator
  • Strain Insulator
  • Shackle Insulator
  • Post-Insulator
  • Stay Insulator
  • Disc Insulator

Pin Insulator

Pin Insulator designed with a high mechanical strength material this kind of insulator is used in electrical distribution systems. This type of insulators are developed for overhead lines, pin type insulator commonly used in power networks voltage up to 33kv. Here pin insulator can be divided into three types such as one part, two part and three part type insulators depends on voltage application.

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types of insulators

Pin Insulator

One part type Insulator: This insulator generally used in a 11kV system where whole pin insulator is one piece of properly shaped glass or porcelain material.

Two part type Insulator: This insulator generally use for 33KV system but in higher voltage systems – like 33KV and 66KV – manufacturing of one part porcelain pin insulator becomes more difficult.

Three part type Insulator: This insulator suitable for higher voltage rating applications up to 66KV systems.

Suspension Insulator

Suspension Insulator similar to the disc insulator and the designing of this insulator can be done using porcelain or glass. It is used in overhead transmission lines by ensuring more flexibility. Suspension insulators provides for higher voltage rating, beyond 33KV and up to 765KV transmission lines, it becomes uneconomical to use. In case of one of the insulator gets failure then remaining all the discs will works properly. So we can change the damaged disc easily.

Suspension Insulator

Suspension Insulator

Rated System Voltage

Number of disc insulator used in suspension insulator string

33KV 3
66KV 4
132KV 8
220KV 14


Strain Insulator

A Strain Insulator is designed to work in mechanical strain (tension), to withstand great tensile load of conductor or strain. They are used in overhead transmission lines at dead end or there is a sharp corner in transmission line has to withstand to tensile load of conductor.

strain insulator

Stain Insulator


Rated System Voltage

Number of disc insulator used in strain type insulator

33KV 3
66KV 5
132KV 9
120KV 15

Shackle Insulator

The shackle insulator is generally used in low voltage distribution network. It is also known as a spool insulator it can be used in both horizontal or vertical positions. Shackle insulators are small in size and used in overhead distribution systems.

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Shackle Insulator

Shackle Insulator

The shackle insulator Voltage capacity is 33KV and it works in bend or circular turn positions. Now a days in low voltage distribution lines these insulators used as strain insulators for cost reduction.

Post Insulator

Post Insulators are similar to Pin insulators, the mechanical strength of this insulators are high. The post insulators are most suitable for high voltage rating applications. It is suitable for lower voltage and also for higher voltage

Stay Insulator

Stay Insulator is very small in size as compared with other Insulators, these are in rectangular shape and is used in the distribution lines. This insulator used only for low voltage lines and the stays are to be insulated from ground its acting like a safety device and that protection against sudden voltage changes.

stay insulator

Stay Insulator



Disc Insulator

Disc insulators are widely used in high voltage transmission and distribution systems, which are designed for providing electro mechanical strength. These insulators are provides a cost effective and medium or low polluted conditions and which are designed with high grade raw materials. The advantages of disc insulator include transmission lines, commercial distribution because it has high efficient like low corrosion, robust design.

disc insulator

Disc Insulator

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