What is Insulator ?It is a material that do not conduct electricity under normal condition.
Or
It is a material whose internal electric charges does not flow freely .
Paper, plastic, rubber, glass and air are insulating material .Vacuum is also the insulator but it is not a material. To protect and safely flow of electric current ,conductors are covered by insulation.
It is rated in hundreds of volts or hundred thousands of volts when it is used in high transmission and distribution system.
Insulating material
1.Glass
2.Plastic
3.Rubber
4.Porcelain
5.Wood
6.Distilled or pure water
7.Ceramic
8.Asphalt
Insulating material properties
The material which is used as a insulator is called insulating material .For successful used and better performance ,an insulating material should have the following properties .
- It should be strong mechanically so that it can carry tension and weight of conductors.
- The material should have high dielectric strength to withstand the stress voltage in case of high voltage system.
- The material should be free from unwanted impurities .
- The material should not be porous.
- Its should be less effected by the temperature.
- There must be an entrance on the surface of it so that the gases or moisture can enter in it
Porcelain insulator
Porcelain are the most commonly used insulating material in the daily life .Its is Aluminum silicate. when aluminum silicate is mixed with the plastic kaolin, feldspar and quartz ,the porcelain insulator formed
The surface of the insulating material should be glazed so that the water should not kept on it .It should be free from porosity because the porosity is the main cause of deterioration of its dielectric property.
Properties of Porcelain
Dielectric Straingth – 60 KV / cm
Tensile Strength — 500 Kg / cm2
Compressive Strength- 70,000 Kg / cm2
Glass insulator
Glass type Ins are becoming more popular now a days in transmission and distribution system due to their some properties . Annealed tough glass is used as a insulating purpose.
Glass insulat0r have many advantage over the porcelain . It has very high dielectric strength as compare to porcelain. The resistivity of glass is very high .Its has very low thermal expansion coefficient.
Due to their transparency the impurities and air bubble can easilt detected inside the glass. The glass insulator has a very long life as compare to other insulators.
Properties of Glass
Dielectric Straingth– 140 KV / cm
Tensile Strength– 35,000 Kg / cm2
Compressive Strength– 10,000 Kg / cm2
Polymer Insulator
It has two parts, one is glass fiber In a polymer insulator has two parts, one is glass fiber reinforced epoxy resin rod shaped core and other is silicone rubber or Ethylene Propylene Diene Monomer (EPDM) made weather sheds. The weather sheds is useful because its protect insulator from outside environment..Due to its two parts it is called composite insulator.
Type of insulator
There are three main types
1.Pin Type
2.suspension type
3-Strain Type
1–Pin type Insulator
The pin type insulat0r are mounted on a pin on a cross-arm with the pole .On the upper end of the insulator there is a groove.
The conductor which is passed through the groove and is tied by annealed wire of same material as of conductor. Pin type ins are used in transmission and distribution up to 33V..
2–Suspension type Insulator
It separate the line conductors and support it electrically. This type consist number of porcelain insulat0r units connected with each other by a metal links which is form a string. The conductor is connected at the bottom of the string.
Each unit of the insulator operate the voltage of about 11KV so depending upon the voltage the disc can be increase and decrease in the string .If one unit damaged then it can be replace by a new without replacing the whole string. The string which can move in any directions
3–Strain Insulator
When there is dead end or sharp corner in the transmission line ,the line has to sustain a great tensile load of the conductor. To support this load strain insulator are used .It must have mechanical strength as well as necessary electrical insulating properties .
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About The Author
hussainbalti40
I am Hussain Syed from Pakistan .i am electrical engineer by profession and working with a well reputed organization which is related to electrical technology .
