VIGNAN INSTITUTE OF TECHNOLOGY AND MANAGEMENT A SEMINAR ON

“INSULATOR IN OVER HEAD LINE”

PRESENTED BY GUIDED BYL.SUSHREE SRABANI DAS PROF.AMAR KUMAR BARIK1221301014

1.INTRODUCTION2.TYPES OF INSULATOR3.INSULATING MATERIAL4.INSULATION FAILURE5.TESTING OF INSULATOR6.USES7. CONCLUSION8.REFERENCE

CONTENT

INTRODUCTION

INSULATOR

INTRODUCTION-Transmission line insulators are device use to contain,separateOr support electrical conductors on high voltage electricity supplyNetworks.

The Insulators provide necessary insulation between line conductor and supports and thus Prevents any leakage current from conductors to earth.

Insulator play an important role in over head line.

PIN TYPE INSULATOR

Pin type insulator is secured to the cross arm on the pole.There is a groove on the upper end of the insulator for housing the conductor.Pin type insulator used in transmission & distribution of electric power voltage up to 33kv.

ADVANTAGES OF SUSPENSION TYPE INSLATOR

1.Each suspension disc is designed for normal voltage rating 11KV(Higher voltage rating 15KV), so by using different numbers of discs, a suspension string can be made suitable for any voltage level. 2.If any one of the disc insulators in a suspension string is damaged, it can be replaced much easily.

3. Mechanical stresses on the suspension insulator is less since the line hanged on a flexible suspension string.

4.It is cheaper than pin type insulator.

SHACKLE TYPE INSULATOR

The shackle insulator or spool insulator is usually used in low voltage distribution network.

It can be used both in horizontal and vertical position. The use of such insulator has decreased recently after increasing the using of underground cable for distribution purpose.

INSULATING MATERIALS

• There are several types of materials are used in over head line i.e glass,wood,mica,porcelain,rubber,fibre etc.

• But in over head line most commonly porcelain is used.

porcelain

INSULATING FAILURE

There are different causes due to which failure of insulation in electrical power system may occur. Let's have a look on them one by one-

1) Cracking of InsulatorThe porcelain insulator mainly consists of three different materials. The main porcelain body, steel fitting arrangement and cement to fix the steel part with porcelain.

2) Defective Insulation MaterialIf the insulation material used for insulator is defective anywhere, the insulator may have a high chance of being puncher from that place.

3) Porosity in The Insulation MaterialsDue to porosity , insulator absorb water from atmosphere and electrical resistance of insulator decreases.

4)Flash Over Across Insulator-If flash over occurs, the insulator may be over heated which may ultimately results into shuttering of it.

5)Mechanical Stresses on Insulator-If an insulator has any weak portion due to manufacturing defect, it may break from that weak portion when mechanical stress is applied on it by its conductor.

TESTING OF INSULATOR

To ensure the desired performance of an electrical insulator, that is for avoiding unwanted insulator failure, each insulator has to undergo numbers of insulator test.

1.MECHANICAL TESTING:If an insulator has any weak portion due to manufacturing defect, it may break from that weak portion when mechanical stress is applied on it by its conductor.2.POROSITY TESTING:In this test insulator broken into pieces and immersed in some kindof dye solution with high3.FLASHOVER TESTING:This test is performed to get the flashover voltage ofcertain insulator.

Flashover testing is 3 types-

Dry flashover test.

Wet flashover test.

Impulse flashover test.

4.PUNCTURE TESTING: This test is performed to find puncture test of an insulator.

In this test, the total insulator is immersed in oil and subjected to a gradually increased voltage.

USES OF INSULATOR

Electrical Insulator must be used in electrical system to prevent unwanted flow of electric current to the earth from its supporting points.

It is mainly used in over head line to hold the bare conductor which carries the voltage and current one end to another end without fail.

The insulator plays a vital role in electrical system. Electrical Insulator is a very high resistive path through which practically no electric current can flow.

CONCLUSION-Insulator is a main part of an overhead line.

So it is mainly used in over head line to hold the bareConductor.

REFERENCE-V .k meheta , power system, 3nd ed., S. Chand publication.

Sue Taylor (May 2003). Bullers of Milton. ISBN 978-1-897949-96-2.

www.Insulating Material _ Porcelain Glass Polymer Insulator _ Electrical4u.htm

Www. Electrical Insulator Testing _ Cause of Insulator failure _ Electrical4u.htm

ANY QUESTION…