Types of Insulator use in Electrical Power System
Insulator is a device which is used to isolate the live conductor from pole and earth. which are manufacture for different voltage ratings. This all type of insulator are use in electrical power system. there are different types of insulators according to their application,
- Pin type
- Shackle type
- Suspension type
- Strain type
- Material used for insulator are following as below:
- Porcelain: when the mixture of kaolin and quartz are taken in certain proportion and it is heated to high temperature, which result to porcelain material. porcelain is used for making the insulators for overhead lines . Dielectric strength of porcelain is 65kv/cm.
- Glass: It is also used for making the insulator. but it has one limitation is difficult to cast when the shape is irregular. moulded tough glass is used. it has very high dielectric strength is 140kv/cm.
- Steatite: its tensile strength is very high compare to the porcelain. it is used for strain type insulator.
Different type of insulator:-
- Pin type :- this type of of insulator is use for less voltage rating is 11KV to 25KV. if there are two piece insulator and three piece insulator then voltage rating is 33KV and 66KV respectively. in pin type insulator threads are cut at the lower portion of the special shape of porcelain. the conductor is placed at the top of the insulator with the help of soft binding wire.
- Construction of its made such that for there is sufficient porcelain between the conductor and pin, so that sufficient dielectric strength is available. The shape of insulator is made corrugated so that length of leakage path is increase to prevent from leakage of current from the conductor to the earth. This portion known as the rain shed. Due to this shed inner portion remain dry even during the rain. this type use in distribution system.
- Suspension type : pin type are use up-to 33kv . it can be design for 66kv but it is become bulky. so instead of this we can use suspension type for voltage rating above 33kv. In suspension type there are different discs depending upon the system voltage. require number of discs are use and it is prepared as in string.
- When any disc damage only that disc can be replace and whole string is not require to be replace. every disc are design for 11kv voltage rating. if voltage rating is 66kv then 6 disc placed in series will be provide on the string. this type is cheaper then pin type. its provide greater flexibility. this insulator use in transmission system.
- Strain type : when line is subjected to greater tension, There is dead en of the line or there is corner. in order to relive the line of excessive tension, strain type are used. its design for low voltage(11kv) . when voltage is low shackle type are use as strain type.
- When voltage rating is high of transmission line strain type are use. which is consist of an assembly of suspension insulator. the disc of strain insulator are use in the vertical direction and axis of insulator is in the horizontal direction.
- Shackle type : in early days the shackle type were use as strain type. but in now a days they both are frequently use for low voltage distribution line. they can be directly mounted on the pole by bolt or U clamp fitted to the cross-arm.
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