Types of insulators – they are i) Pin type insulator, ii ) Suspension insulators {a. Hewlett suspension type b. Cemented cap type c. Core and link type}, iii. Strain insulator, iv. Shackle insulator, v. Stay type insulator

Basic Electrical Engineering

Types of insulators

i. Pin type insulator

ii. Suspension insulators

a. Hewlett suspension type

b. Cemented cap type

c. Core and link type

iii. Strain insulator

iv. Shackle insulator

v. Stay type insulator

i. Pin type insulator

This type of insulator is fixed in the crossing arm of the pole. The conductor is placed in the top of semicircular groove and the conductor is placed on it. This type of insulator is used to capture straight conductors

ii. Suspension insulators

The suspension type. This insulator is in hanging shape and is connected to the steel tower. The line conductor is connected in the base. In suspension type insulator, a number of similar units are connected one by one with bi-metallic links. Each suspension insulator is designed for 11KV. Therefore, by connecting a number of such insulator discs, a string of insulator can be designed for any required voltage.

a. Hewlett type

The insulator part is made up of porcelain material. In the middle of the structure, a U shaped groove is provided. Using metal connectivity on it, more than one circular plates are connected through the screws. If the insulator is broken the conductor does not fall down.

b. Cemented cap type

This insulator unit is made up of porcelain. The galvanized cast iron cap is cemented to the top. A steel screw is cemented to the cavity at the bottom. The other end of the steel screw is placed in the ball shape to fit into the pit in the back of the iron cap.

c) Core and link type

It is a combination of both the above two types of suspension insulators. It is better than the above two types. In this type, porcelain discs are placed symmetrically. The metallic cylinder is pressed and tied to the fringe circular of porcelain plate. This type of insulators are unaffected by temperature.

iii. Strain type insulators

These insulators are used in places where there are very high tensions such as dead ends, sharp curves, corners and line which crosses the river. This type of insulator can be used for low voltages up to 11 KV. For the longer spans across river, two or more strings of insulators are used in series. Two or more strings of insulators are used in parallel where having high tensions.

iv. Shackle insulator

This type of insulator mostly used for low voltage distribution lines. Such insulators can either be used in a horizontal position or in a vertical position.

v. Stay insulator

The insulator used in the stay wire is called a stay insulator. This type of insulator is made of porcelain. The size of insulator depends upon the tensile strength of stay wire. It is used to prevent the leakages from the poles up to 33KV. These are provided at a height of 3m from the ground level.

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