Types of Insulator
Pin type insulator
2. Suspension type insulator
3. Strain type insulator
4. Shackle Type insulator
Theory of Insulator
The over head line conductor should be Supports on poles in such a way that current from conductor do not flow to earth through the supports this is achieved by searing line conductor to supports with the help of insulator. The insulator provided necessary insulator between line conductors.
The insulator should have the following property.
A. High mechanical strength in order to with stand conductor load wind load etc.
B. High electrical resistance of insulator material as in order to avoid leakage current to earth.
C. High relative permittivity of insulator material in order that dielectric strength is high.
D. The insulator material should be non porous free from impurities and Greeks otherwise the pa mites will be lower. The most commonly used material for insulator of over head line is porcelain but and special composition material are also used to a limited range. Porcelain is produced by fixing air high temperature a mixture of kaolin fields and generate. It is stronger mechanical then glass givers less trouble from leakage and is less affected by changes of temperature.
Types of Insulator
1. Pin type Insulator
The pin type insulator fixed to the cross arm on the poles. There is grove on the upper end of the insulator for housing the conductor passes through this groove and is wound by annealed wire of the same material as conductor pin type insulator are for transmission and distribution of electric power voltage up to 33Kv become operating voltage of 33KV The Pin type insulator because too bulky and hence in economy.
2. Suspension type Insulator
The cost of pin type insulator increase rapidly as the working voltage is increased for high voltages.
It is usual practices to use Suspension type insulator.
A consist of no. of porcelain disc in connected in series by metal link by in the form of spring. The conductor is suspended at the bottom end of this string by the other end of the spring connected to the cross arm of the tower. Each this design for a low voltage.
3. Strain type Insulator
When there is a dead end of the line or there is corner or sharp curve the line realizes a greater tension. In order to relive the line excessive tension, strain insulator are used . For low voltage lines shackle insulators are used as strain insulator.
4. Shackle Insulator
In early days the shackle type insulator were used as strain insulator but in the present time distribution lines. Such insulators can be used either in horizontal position or in vertical position
The main advantages of suspension type insulator
· Suspension type of insulators are cheaper then pin or other type insulator they on 33Kv
· Each unit of suspension type insulator is design for a low voltage .internally 11kv.
· If one disk is damaged, the whole string does not become use less because the damaged disk can be replace by another one.
· The Suspension arrangement provided greater flexibility to the time.
· The suspension type insulators are generally used with still tower.