Types of Insulators Used in Transmission
(Overhead) Lines
Type of Insulators Used in Transmission lines
There are 5 types of insulators used in transmission lines as overhead insulation:
1. Pin Insulator
2. Suspension Insulator
3. Strain Insulator
4. Stay Insulator
5. Shackle Insulator
Pin, Suspension, and Strain insulators are used in medium to high voltage systems. While Stay
and Shackle Insulators are mainly used in low voltage applications.
Pin Insulator
Pin insulators are the earliest developed overhead insulator, but are still commonly used in
power networks up to 33 kV system. Pin type insulator can be one part, two parts or three parts
type, depending upon application voltage.
In a 11 kV system we generally use one part type insulator where whole pin insulator is one
piece of properly shaped porcelain or glass.
, As the leakage path of insulator is through its surface, it is desirable to increase the vertical
length of the insulator surface area for lengthening leakage path. We provide one, two or more
rain sheds or petticoats on the insulator body to obtain long leakage path.
In addition to that rain shed or petticoats on an insulator serve another purpose. We design these
rain sheds or petticoats in such a way that while raining the outer surface of the rain shed
becomes wet but the inner surface remains dry and non-conductive. So there will be
discontinuations of conducting path through the damp pin insulator surface.
In higher voltage systems – like 33KV and 66KV – manufacturing of one part porcelain pin
insulator becomes more difficult. The higher the voltage, the thicker the insulator must be to
provide sufficient insulation. A very thick single piece porcelain insulator is not practical to
manufacture.
In this case, we use multiple part pin insulator, where some properly designed porcelain shells
are fixed together by Portland cement to form one complete insulator unit. We generally use two
parts pin insulators for 33KV, and three parts pin insulator for 66KV systems.
Post Insulator
Post insulators are similar to Pin insulators, but post insulators are more suitable for higher
voltage applications.
Post insulators have a higher number of petticoats and a greated height compared to pin
insulators. We can mount this type of insulator on supporting structure horizontally as well as
(Overhead) Lines
Type of Insulators Used in Transmission lines
There are 5 types of insulators used in transmission lines as overhead insulation:
1. Pin Insulator
2. Suspension Insulator
3. Strain Insulator
4. Stay Insulator
5. Shackle Insulator
Pin, Suspension, and Strain insulators are used in medium to high voltage systems. While Stay
and Shackle Insulators are mainly used in low voltage applications.
Pin Insulator
Pin insulators are the earliest developed overhead insulator, but are still commonly used in
power networks up to 33 kV system. Pin type insulator can be one part, two parts or three parts
type, depending upon application voltage.
In a 11 kV system we generally use one part type insulator where whole pin insulator is one
piece of properly shaped porcelain or glass.
, As the leakage path of insulator is through its surface, it is desirable to increase the vertical
length of the insulator surface area for lengthening leakage path. We provide one, two or more
rain sheds or petticoats on the insulator body to obtain long leakage path.
In addition to that rain shed or petticoats on an insulator serve another purpose. We design these
rain sheds or petticoats in such a way that while raining the outer surface of the rain shed
becomes wet but the inner surface remains dry and non-conductive. So there will be
discontinuations of conducting path through the damp pin insulator surface.
In higher voltage systems – like 33KV and 66KV – manufacturing of one part porcelain pin
insulator becomes more difficult. The higher the voltage, the thicker the insulator must be to
provide sufficient insulation. A very thick single piece porcelain insulator is not practical to
manufacture.
In this case, we use multiple part pin insulator, where some properly designed porcelain shells
are fixed together by Portland cement to form one complete insulator unit. We generally use two
parts pin insulators for 33KV, and three parts pin insulator for 66KV systems.
Post Insulator
Post insulators are similar to Pin insulators, but post insulators are more suitable for higher
voltage applications.
Post insulators have a higher number of petticoats and a greated height compared to pin
insulators. We can mount this type of insulator on supporting structure horizontally as well as
