Definition: Materials that do not allow current to pass through them are called electrically insulating materials. The insulating material provides a high resistance path for the current, and it is almost impossible for the current to conduct through the current. Simply put, the electrical insulation material does not move freely. It is used for overhead transmission lines between the tower and the conductor to prevent current from flowing from the conductor to the ground.
Characteristics of electrical insulation materials
The insulating material should have the following characteristics.
1. In order to carry the weight and tension of the conductor, it is necessary to have a high mechanical strength.
2. He needs to have high dielectric strength.
3. To prevent leakage current from flowing from the conductor to ground, the material needs to have high resistance.
4. The material is non-porous and free of impurities.
5. The electrical and chemical properties of the material should not be affected by temperature.
The electrical insulator is made of tempered glass or high quality wet porcelain. Porcelain is usually painted brown on the entire exposed surface, but sometimes a creamy glazed insulator is used.
Prestressed or tempered glass has been used to construct line insulators. The surface layer of the tempered glass insulator is in a highly compressed state, thereby being resistant to high mechanical and thermal stresses. The insulating material is toughened by heating the material above its strain temperature and the air on its surface is cooled.
The following are the advantages of tempered glass insulators versus porcelain insulators.
1. Tempered glass insulators have higher puncture strength.
2. They have higher mechanical strength and therefore less damage during transportation and installation.
3. They have high heat reserves and resistance, thus reducing damage caused by power flashover.
4. If the insulator is damaged by electrical and mechanical reasons, the casing ruptures and falls on the ground. The cap and pin maintain sufficient strength to support the conductors they are positioned in.
5. The life of tempered glass insulators is very long.
A disadvantage of glass insulators is that moisture easily condenses on its surface. However, when the puncture strength in the air is tested with a steep shock wave, the performance of the glass insulator is similar to that of the porcelain unit.
The polymer insulation material is used as an electrical insulation material. It consists of a combination of fiberglass and epoxy polymer instead of porcelain. Polymer insulators are 70% lighter than equivalent porcelain units.
Characteristics of Polymer material：
1. Anti-piercing and high mechanical strength.
2. Its high thermal resistance characteristics can reduce flash damage.
3. Excellent radio interference voltage performance,
4. Smaller hardware corrosion and better performance in a polluted environment.