electrical insulator

Electrical Insulator and why we use them

Electricity is no joke

In today’s world from lighting a bulb to charging your brand new tesla, electricity is a crucial part of our lives. But as much as electricity is helpful, it is a dangerous thing also ( if used irresponsibly ).

Materials that pass electricity or electric current through them are called conductors. As much as conductors are useful in current conduction, electrical insulators are in resisting the flow of current.

Today here we understand what is an insulator and why we use them.

What is an electrical insulator?

Insulators are material which does not conduct electricity. They do so by providing resistance to the electrical current.

Mostly the electrical conductors are covered with some insulating material (it may be solid, liquid, or any other element), which prevents the unnecessary flow of the current.

For eg. all of us have seen an electrical wire, the current-conducting material (copper, aluminium, etc.) is covered with some plastic-type material. That is PVC (polyvinyl chloride) or PE (polyethylene) an insulating material.

Energy band of an insulator

The energy band of the insulator is shown below:

energy band diagram of electrical insulator

Insulators are known to restrict the current flow. The energy band of the insulator consists of the conduction band and valence band. Unlike conductor or semiconductor, the forbidden energy gap between the valence band and the conduction band is so high that the free electrons present in the valence band are not able to move to the conduction band. Therefore, insulators do not conduct.

Classification of an electrical insulator

Insulators are classified based on the 2 following things:

Classification based on the insulating material

  • Solid
  1. Glass
  2. Wood
  3. Porcelain
  4. Mica
  5. PVC, etc.
  • Liquid
  1. Linseed oil
  • Gases
  1. Carbon dioxide
  2. Nitrogen
  3. Argon, etc.

Classification based on the temperature

Types of electrical insulator

Pin insulator

Pin type is one of the earliest developed and the most commonly used insulators. It is still used in transmission lines up to 33kV. This type of insulator is usually made up of porcelain or sometimes glass.

Post insulator

The post type is similar to the pin type insulator. Like pin type, post type insulator is also made from porcelain. It has more rain sheds (petticoats) and the conductor connected on both the top and bottom side is connected by a clamp.

There are two types of post insulators listed below:

  • Line post insulator

Line post insulators are made of porcelain. It can be used for voltages up to 132kV.

  • Station post insulator

Station post insulators are generally used for high voltage switches and substations. It requires minimum maintenance because the coating on the exterior side of the insulator keeps dirt and other pollutants adhering to it. Mostly it is used vertically.

Strain insulator

A strain insulator is used for high voltage transmission lines. It is used to support the horizontal tension of long wires. Depending on the tension load, more strain insulators can be added in parallel.

Suspension insulator

The suspension insulator works for voltage beyond 33kV. Few discs made of glass or porcelain are connected in series by a metallic string. The bottom end of the string is connected to a conductor and the upper end is connected to the tower.

The number of discs used can be changed depends on the voltage.

Shackle insulator

In the past, a shackle insulator is used as a pin insulator but in today’s world, it is used for low voltage lines. It can be used in both horizontal and vertical positions.

Long road insulator

Long road insulators are used in high voltage lines. It can bear many loads like wind load, ice load, etc. continuously for a long time.  

Stay insulator

Porcelain is used to make stay insulators. This insulator is connected to the stay wire, so when the tower falls to the ground the lower end of the wire doesn’t conduct current.

Properties of insulator

  • It does not allow the electric current to flow through it i.e it produces high resistance.
  • Insulators do not have free electrons which conduct electricity.
  • An insulator has a vast dielectric strength.
  • High air permeability.

Why do we use an insulator?

  • For safety purposes: an electrical insulator does not allow the current to flow through it. So when working with high voltage applications an electrical insulator helps in keeping the operator safe from very high current.
  • For controlled operations: as the insulator can restrict the flow of current, the electrical systems without any insulator result in a failed operation. It is the insulator that helps in controlling the current flow and better transmission of current.

Application of electrical insulator

Electrical insulators are used for restricting the flow of current. Few applications where insulators are used are listed below:

  • Used as a coating for a conducting cable
  • Used in overhead transmission line
  • Used in electrical machines

Quick summary

Electrical insulators do not allow the electrical current to pass through it. You can see it around the overhead transmission lines or coating around the conducting cables in everyday life.

It is classified based on the materials and the temperature. There are few types of electrical insulators like pin type, post type, suspension type, etc.   

So, it is a good practice to use insulating equipment like a rubber glove, etc. during working with an electrical system.

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