Electrical Insulating Material

Definition: The material which does not allow the electricity to pass through them is known as an electrical insulating material. The charge of the insulating material does not move freely, or in other words, it provides the high resistive path to the electric current through which it is nearly impossible for the electric current to conduct through it. It is used in the overhead transmission line between the tower and conductor for preventing the flow of electric current from the conductor to earth.

Properties of an Electrical Insulating Material

The insulating material should have the following properties.

  1. The material must have high mechanical strength so that it carries the tension and weight of the conductors.
  2. They must have high dielectric strength.
  3. The material is highly resistive for preventing the flow of leakage current from the conductor to earth.
  4. The material is non-porous and free from impurities.
  5. The electrical and chemical property of the material should not be affected by the temperature.

The electrical insulator is produced from toughened glass or high-quality wet process porcelain. The porcelain is usually glazed in brown colour overall exposed surface, but sometimes cream glazed insulator are also used.

Pre-stressed or toughened glass has been employed in constructing line insulator. The surface layer of the toughened glass insulator is in the state of high compression due to which it can resist the high mechanical and thermal stress. The insulation material is toughened by heating the material above its strain temperature, and it is cool from the air on its surface.

The following are the advantages of toughened glass insulators over porcelain insulator.

  1. The toughened glass insulator has greater puncture strength.
  2. They possess greater mechanical strength and, therefore, there is less breakage in transport and installation.
  3. They have high thermal stock, resistance and, therefore, damage from power flashover is reduced.
  4. If an insulator is damaged by electrical and mechanical cause,  the outer shed breaks and fall on the ground. The cap and pin remain sufficiently strong to support the conductor in it’s positioned.
  5. The life of the toughened glass insulator is long.

The glass insulator has the disadvantages that the moisture readily condenses on its surfaces. But the performance of the glass insulator is practically similar to that of porcelain unit when tested for puncture strength in the air with steep-fronted impulse waves.

The polymer insulator material is used as an electrically insulating material. It is made up of a combination of fibreglass and an epoxy polymer instead of porcelain. The polymer insulator is 70 percent lighter than its equivalent porcelain unit.

The polymer material is puncture proof and has a high mechanical strength. It has high thermal resistance to reduce the damage of flash over, excellent radio interference voltage performance, lesser hardware corrosion, and better performance in polluted atmospheres.

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