Common Types of Insulators Used in Power Transmission Lines

An insulator is a material that does not allow electricity to flow freely. This is due to the insulator’s electrons being more tightly bonded and unable to move freely. Paper, plastic, rubber, glass, and air are all common insulators. Semiconductors and conductors are non-insulator materials, meaning they can easily conduct electric currents. Insulators have higher resistivity than semiconductors or conductors. They’re mostly used to protect materials that conduct electricity.

For instance, the plastic cover that surrounds the wires stops electricity from flowing where it isn’t required. Furthermore, insulators are utilized to connect power distribution and transmission cables to utility poles and transmission towers. In this article, you’ll learn the different types of insulators used in power transmission lines. You’ll also the advantages and disadvantages of these insulators.



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Types of Power Transmission Insulators

The following are the common types of insulators used in power transmission lines:

  1. Disc insulators
  2. Post insulators
  3. Pin insulators
  4. Strain insulators
  5. Suspension insulators
  6. Shackle insulators
  7. Stay insulators
  8. Polymer insulators
  9. Glass insulators
  10. Long rod insulators

Disc insulators

These types of insulators get their name from the shape of the insulator, which resembles a disc. In high-voltage transmission and distribution lines, these insulators are utilized. The requisite electro-mechanical strength is met by disc insulators.
Furthermore, they are a cost-effective option for polluted regions with medium to low levels of pollution. Transmission lines and industrial and commercial applications are among the uses for these insulators, which have high-efficiency qualities such as reduced corrosion and a strong design. In suspension and tension systems, they provide insulation as well as support for line conductors. It can also maintain high voltages in heavy-load situations.

disc insulator

Post insulators

This type of transmission line insulator is a high-voltage insulator that can handle a variety of voltage levels, making it ideal for use in substations. These are used to ensure that electricity generated in power plants is distributed safely and reliably.

Post insulators are constructed of ceramic or a single piece of composite material (silicone rubber) and may hold up to 1100 kV of power. Because of its outstanding mechanical qualities, it is commonly used to protect transformers, switchgear, and other connected equipment when mounted vertically.

post insulator


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Pin insulators

Pin types of insulators are typically seen in power distribution lines. It’s a device that protects a wire from physical support, such as a utility pole pin (wooden or metal dowel). It’s a single-layer, non-conducting shape composed of porcelain or glass.

Depending on the voltage application, one or multiple pin insulators might be utilized on the physical support. The pin insulator is developed with a high mechanical strength material and can carry voltages up to 11kV. These can be positioned either vertically or horizontally.

pin insulator

Strain insulators

These types of insulators are made to withstand the stretch of a hung electrical wire or cable when subjected to mechanical stress. It is used to support radio antennae and overhead power lines, similar to a suspension insulator.

Between two lengths of wire, a strain insulator is used to electrically disconnect them while preserving a mechanical connection. Alternatively, it can be utilized to deliver the pull of wire to support while electrically insulating it when a wire links a pole or tower. The voltage potential of these insulators is around 33kV.


Suspension insulators

Insulators like this are commonly employed as conductors to safeguard overhead transmission lines. The suspension insulator is a type of insulator that is widely used in towers and is composed of porcelain. They have a form string with a succession of insulators linked to it.

It is hinged on the tower’s cross arm and has a power conductor at its lowest point. When a higher voltage of around 33 kV is required, they are employed. As the size and weight of the insulator increase, the pin insulator becomes more cost-effective. A suspension insulator is utilized to solve these challenges.



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Shackle insulators

Shackle types of insulators are utilized in low voltage distribution systems and are typically tiny in size. This kind of insulator can be utilized both vertically and horizontally. This insulator can be connected with a metal strip and has a voltage carrying capacity of roughly 33 kV.

It has a tapered hole that evenly distributes the load force, lowering the risk of fracture when highly loaded. After the widespread usage of subterranean cables for distribution, the use of insulators has declined recently.

shackle insulator

Stay insulators

Stay types of insulators are low-voltage insulators that combine a stay wire and a primary grip to balance and fasten dead-end poles. These insulators are rectangular and come in smaller sizes than other types of insulators.

Between the line conductor and the earth, these insulators can be placed. Furthermore, they serve as protection devices, guarding against abrupt voltage changes due to faults. When the poles collapse to the ground or the stay wires are accidentally damaged owing to increased mechanical load, the value of these insulators is evident.

stay insulator

Polymer insulators

These types of insulators are electrical devices that are typically made of polymer materials with metal fittings. Furthermore, these insulators are enclosed by polymer weather shelters and are formed of fiberglass rods. The insulator core is protected from the elements by weather shades.

Polymer insulators are lighter than porcelain insulators and provide more power. It is generally thought to be a good heat and electrical insulator. Because of its unusual electrical, mechanical, chemical, and thermal qualities, it is utilized as an insulator.



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Glass insulators

These types of insulators are made of annealed or toughened glass that is used in power transmission lines. This insulator’s job is to insulate electrical lines so that electricity does not leak into all of the poles and the ground.

In the past, glass insulators were employed in telegraph and telephone lines, but in the 19th century, ceramic and porcelain varieties took their place. Toughened glass kinds were produced to counter the glass’s frailty, and they quickly became popular due to their extended lifespan.

glass insulator

Long rod insulators

To insulate transmission lines, long rod insulators are commonly hinged on steel towers. Furthermore, they serve as safety devices by properly supplying power. Long rod insulators are usually made up of many insulators, depending on the usage and demand.

On the outside, these are porcelain rods with weather sheds and metal end fittings. This type of insulator has the advantage of being able to be used in both tension and suspension applications.

long rod insulator


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That is all for this article, where the common types of insulators used in transmission lines are been discussed. I hope you learn a lot from the reading, if so, kindly share with other students. Thanks for reading, see you around!