INSULATORSIS:731-1971 Porcelain insulators for overhead Power lines with a nominal

Voltage greater than 1000 V

IS:3188-1965 Dimensions for disc insulators

160 KN EM Strength Porcelain Disc Insulators –

160 KN EM strength Disc Insulators shall be used in the following Insulator strings along with hardware fittings:

Single tension Insulator strings (1x26) for angle towers.Double tension Insulator strings (2x25) for angle towers.Triple tension Insulator strings (3x25) for angle towers and crossings.

In the event of supply of insulators conforming to Standards other than specified, the Bidder shall confirm in his bid that these standards are equivalent to those specified. In case of award, salient features of comparison between the standards proposed by the Bidder and those specified in this document will be provided by the supplier to establish equivalence.

Sl.no Indian Standards TITLE International standard----------------------------------------------------------------------------------------------------------------------------1. IS 731-1974 Porcelain insulators for BS:137-1982

over head power lines with (I & II) a nominal voltage greater than 1000 V IEC:383-

(Part-I)-1993, (Part-II)-1992

TECHNICAL DESCRIPTION1 Details of Disc Insulators1.1 The Insulator of the strings shall consist of standard discs for a three phase, 50

Hz, effectively earthed 400 KV Transmission system in a moderately polluted atmosphere. The discs shall be cap and pin, ball and socket type.

1.2 Bidder shall quote for disc insulators made of electro porcelain in accordance with the above clause

1.3 The size of disc insulator, minimum creep age distance, the number to be used in different types of strings ,their electromechanical strength and mechanical strength of insulator strings along with hardware fittings shall be as in Table below:

PARTICULARS OF INSULATORS AND INSULATOR STRINGS---------------------------------------------------------------------------------------------------------------------------SL# PARTICULARS SINGLE SINGLE „I‟ SINGLE DOUBLE

SUSPENSION SUSPENSION TENSION TENSION"I" PILOT STRING STRING STRINGSTRING

----------------------------------------------------------------------------------------------------------------------------1. No. of standard disc 1X26 1x26 1X26 2x252. Size of disc-mm 255x145 255x145 280x170

280x170or 280x145 or 280x145

3 E&M Strength 120 KN 120 KN 160 KN 2x160 KN

(kg) each string4 Ball and socket 20 20 20 20

Designation (mm)5 Creep age distance

of each disc( mm) 315 315 330 3306 Weight of 250 250 250 500

Insulator strings (Kg.)

2 DIMENSIONS OF INSULATOR DISCS2.1 It shall be ensured that the dimensions of the disc insulators are within the limits specified below:a) Diameter of disc (mm) standard Maximum Minimum

120 KN Disc 255/280 266/293 244/267160 KN Disc 280 293 267

b) Ball to Ball spacing between discs (mm) :120 KN Disc 145 149 141160 KN Disc 170 175 165

Specifications

Profile: Anti fog, normal, open profile

Mechanical strength: up to 420 KN

Creep age distance: up to 690 mm

Applicable standards: IS, IEC, BS, ANSI, Australian specifications

Salient featuresSuspension insulators (Disc porcelain) are the most widely used models for transmission and distribution lines. Their design varies to suit different types of polluted zones and mechanical strength as per customer's requirements. 

Insulators:The towers are being insulated by usingthe insulator sets which are chosen by dependingo n t h e i r i n s u l a t i o n c a p a c i t y l e v e l s . T h e r e i s porcelain and polymer insulators together havegiven place in this prestigious project oft ransmiss ion   l ine. The porce la in i s used,where there was the high mechanical strength requiredand on the  other hand the po lymer i s used, where t h e e a s y   a c c e s s i n g   o f   m o b i l i z a t i o n o f   t h e m a t e r i a l h a s b e e n r e q u i r e d . A n d a l s o t h e   p o l y m e r insulators served the purpose where the towersare existed with more angle deviations.