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Topic : Insulator
Paper Name: Seminar
Paper Code: PW-EE-782
Name of the Student: Prakas Chandra Bhowmik
Present Semester: 7th
University Roll No.: 28101619017
Gargi Memorial Institute of Technology
Department of Electrical Engineering

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Contents
 Introduction.
 Type of insulator.
 Properties of Insulator.
 Testing of Insulator.
 Causes of Insulator failure.
 Application of Insulator.
 Reference.
 Conclusion

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Introduction
Insulator is a material in which electric current does not flow
freely. The atoms of the insulator have tightly bound electrons
which cannot readily move.
Insulator provide insulation between the line conductor or
support thus prevent any leakage current from conductor to
earth.
Insulators are made from glass,
porcelain or composite polymer
materials.

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Type of Insulator
i. Pin type insulator
ii. Suspension insulator
iii. Strain type insulator
iv. Stay insulator
v. Shackle insulator
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 Pin type insulator
 Pin type insulator are used for Transmission and distribution of pow
er network up to 33kv .
 Pin type insulator can be one part, two parts or three parts type, dep
ending upon voltage.
 One part Pin Insulator for 11kv System.
 Two part Pin insulator Is Used for 33 kv
System.
 Three part pin insulator is Used for 66kv
System.
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 Suspension insulator
 For high voltages(>33kv), It is usual practice to use suspension type
insulators consist of a number of porcelain Discs Connected in serie
s.
 Each unit or disc is designed for 11kv
 The conductor is suspended at the bottom end of
the strung while the other end of the string is
secured to the cross arm of the tower.
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 Strain Insulator
 This type of insulator used When there is dead end of the line or cor
ner or sharp curve.
 For low voltage line 11kv.
 The discs of strain insulator are used in the vertical plane.
 In order to relive the line of excessive tension, strain insulator are us
ed .
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 Stay Insulator
 Stay insulator is a type of low voltage insulator designed to fasten an
d counterweight the dead end pole by connecting with stay wire ,it is
also called stay type insulator or egg insulator.
 There are two holes in the stay insulator body. The 2 pieces guy grip
s go through from the hole in the opposite direction. The guy grip will
wrap the stay wire to furnish the connection.
 It is used in low voltage line
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 Shackle Insulator
 They can be Directly fixed to the pole with a bolt or to the cross arm.
 It can be used both in horizontal and vertical position.
 Mostly used distribution purpose.
 The conductor in the groove is fixed with a soft binding wire.
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Properties of Insulator
1. Mechanically Strong.
2. High insulation Resistance.
3. High dielectric strength.
4. High Relative permittivity.
5. Free from internal impurities.
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Testing of insulator
1. Mechanical strength test.
2. Electrical insulation test.
3. Environment test.
4. Corona test.
5. Temperature test.
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Causes of Insulator failure
1. Flashover: -The most common cause of the insulator fai
lure is the flashover, that causes unequal expansion of t
he porcelain thereby shattering the insulator with big cra
cks.
2. Cracking of insulator: -This cause occurs due to unequa
l expansion of steel, porcelain and cement during the va
rying conditions of cold and heat.
3. Mechanical stresses.
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Application of insulator
1. It is used in transmission and distribution of electricity s
upply.
2. It is provide necessary safety for human and animals.
3. Many electronic components used insulation materials l
ike plastic.
4. Electricity supply board used insulation.
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 Reference
 www.Wikipedia.com
 www.electrical4u.com
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 Conlusion
Thus a brief idea about the types of insulator
used in overhead transmission line has been
obtained. Each type of insulator is having it's
own area of application. The system was
having a flaw that proper track record of the
insulator and poles. damaged or replacement
was not taken care of.
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Thank You