TYPES OF PORCELAIN INSULATORS IN POWER SYSTEMS

1. Disc insulators/Suspension insulators/Tension insulators

Standard type for normal area & Fog type for heavy pollution area.

In suspension insulator numbers of insulators are connected in series to form a string and the line conductor is carried by the bottom most insulator. Each insulator of a suspension string is called disc insulator because of their disc like shape.

2. Pin tye insulators

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.

3. Station post insulators

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 vertically. The insulator is made of one piece of porcelain and it has clamp arrangement are in both top and bottom end for fixing.

4. Line post insulators

Line post insulators are solid core wet process porcelain and are manufactured and tested in conformance with ANSI Standard C29.7, the insulators can be divided into four separate groups-tie top designs, and clamp top designs of vertical, horizontal stud mount and horizontal gain base application.

All insulator hardware (clamp yokes and bases) is ferrous.

Color is gray or brown.

5. Stay and Shackle insulators

For low voltage lines, the stays are to be insulated from ground at a height. The insulator used in the stay wire is called as the stay insulator and is usually of porcelain and is so designed that in case of breakage of the insulator the guy-wire will not fall to the ground.

The shackle insulator (also known as a spool insulator) is usually used in low voltage distribution network. It can be used in both the horizontal or vertical positions. The use of such insulator has decreased recently after increasing the using of underground cable for distribution purpose.

The tapered hole of the spool insulator distributes the load more evenly and minimizes the possibility of breakage when heavily loaded. The conductor in the groove of shackle insulator is fixed with the help of soft binding wire.