The successful operation of an overhead line depends to a considerable extent upon the proper selection of insulation. There are several types of insulators but the most commonly used are pin type, strain insulator, shackle insulator and suspension type.
- Pin type insulator
- Suspension type insulator
- Strain insulator
- Shackle insulator
Pin type insulator-
As the name suggests, the pin insulator is secured to the cross-arm on the pole. There is a groove on the top of the insulator to hold the conductor. The conductor passes through groove and is bound by the same material as the conductor.
Pin type insulator are used for transmission and distribution of electrical power at voltage up to 33kv.Beyond operating voltage of 33kv, the pin type insulator become too bulky and hence uneconomical
Suspension type insulator-
The cost of pin type insulator increases if the voltage capacity will increased. Therefore, this insulator is not economical preferred beyond 33kv. for high voltage (>33kv), it is usual practice to use suspension type insulators.
A number of porcelain discs are connected in series to form this insulator. Each unit disc is designed for low voltage. Say 11kv. The number of discs in series will vary with vary in working voltage. If the voltage is 33 KV then three disc is required in series.
- Suspension type insulator are cheaper then pin type insulator for voltage beyond 33kv.
- If anyone disc is damaged, the whole string does not became useless because the damaged disc can be replaced by the sound one..
- Depending upon the working voltage, the desired number of discs can be connected in series.
In high voltage line, strain insulator are used. For low voltage transmission line, strain insulator consists of an assembly of suspension insulators. The disc of strain insulator are used in the vertical plane.
In early days, the shackle insulator
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