IS-283, Indian Standard for Porcelain Insulator for telegraph and telephone lines.

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B U R E A U O F I N D I A N S T A N D A R D S

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

IS : 283 - 1976

(Reaffirmed 2001)

Edition 4.4

(2003-09)

Price Group 5

Indian StandardSPECIFICATION FOR

PORCELAIN INSULATORS FORTELEGRAPH AND TELEPHONE LINES

( Third Revision )

(Incorporating Amendment Nos. 1, 2, 3 & 4)

UDC 621.315.62 : 621.315.612.2 : 621.39

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IS : 283 - 1976

© BIS 2004

BUREAU OF INDIAN STANDARDS

This publication is protected under the Indian Copyright Act (XIV of 1957) and

reproduction in whole or in part by any means except with written permission of the

publisher shall be deemed to be an infringement of copyright under the said Act.

Indian Standard

SPECIFICATION FORPORCELAIN INSULATORS FOR

TELEGRAPH AND TELEPHONE LINES

( Third Revision )

Electrical Insulators and Accessories Sectional Committee, ETDC 3

Chairman Representing

SHRI L. C. J AIN Ministry of Energy

Members

A DDITIONAL CHIEF ENGINEER, POSTS

AND TELEGRAPHS, J ABALPUR

DIRECTOR OF TELEGRAPHS (L)( Alternate )

DIVISIONAL ENGINEER,TELEGRAPHS (C) ( Alternate )

Directorate General of Posts and Telegraphs(Department of Communications),New Delhi

SHRI V. R. A NANTHANARAYANAN Bengal Potteries Limited, Calcutta

SHRI CHANDER P ARKASH ( Alternate )

SHRI N. S. S. A ROKIASWAMY Tamil Nadu Electricity Board, Madras

SHRI P. S. THIRUNAVUKKARASU ( Alternate )

DR A. S. BHADURI National Test House, Calcutta

SHRI S. K. MUKHERJEE ( Alternate )

SHRI B. N. BHAGAT

SHRI B. C. D AW ( Alternate ) All India Pottery Manufacturers’ Association,

Calcutta

SHRI D. S. CHABHAL Directorate General of TechnicalDevelopment, New Delhi

SHRI A. K. CHOPRA

SHRI NIRVAIR SINGH ( Alternate )Punjab State Electricity Board, Patiala

SHRI A. N. DEB

SHRI A. C. BOSE ( Alternate )Damodar Valley Corporation, Calcutta

DIRECTOR OF RESEARCH Maharashtra State Electricity Board, Bombay

DIRECTOR (TRACTION AND

INSTALLATION)DEPUTY DIRECTOR STANDARDS

(OHE) ( Alternate )

Research, Designs and StandardsOrganization (Ministry of Railways),Lucknow

( Continued on page 2 )






IS : 283 - 1976

2

( Continued from page 1 )

Members Representing

DIRECTOR (TRANSMISSION)DEPUTY DIRECTOR

(TRANSMISSION) ( Alternate )

Central Electricity Authority, New Delhi

SHRI H. M. S. LINGAIAH Karnataka Electricity Board, Bangalore

SHRI G. S. M AHAGAONKAR Mysore Porcelains Ltd, Bangalore

SHRI M. L. MITTAL

SHRI S. P. SINGH ( Alternate )

Bharat Heavy Electricals Ltd, Bhopal

DR G. M. PHADKE

SHRI K. N. J AYARAM ( Alternate )

Indian Electrical Manufacturers’ Association,

Bombay

SHRI P. S. R AMAN

SHRI E. P. WILFRED ( Alternate )

New Government Electric Factory Ltd,

Bangalore

SHRI M. K. S ANKARALINGAM

SHRI G. R. BHATIA ( Alternate )

Directorate General of Supplies and Disposals,

New DelhiSHRI K. M. S ANKARAN

SHRI P. R AO ( Alternate )

Rural Electrification Corporation Ltd,

New Delhi

SHRI N. S. SEETHURAMON

SHRI V. SRINIVASAN ( Alternate )

W. S. Insulators of India Ltd, Madras

DR U. S. SINGH

SHRI A. D. DUA ( Alternate )

High Tension Insulator Factory, Ranchi

SHRI SURENDRA SINGH

SHRI T. B. L. SRIVASTAVA

( Alternate )

U. P. Government Pottery Development

Centre, Khurja

SHRI L. V ENKATASUBBU

SHRI R. V. A CHUTHAN ( Alternate )

Seshasayee Industries Ltd, Vadalur Post

(South Arcot District)

SHRI S. P. S ACHDEV ,Director (Elec tech)

Director General, ISI ( Ex-officio Member )

Secretary

SHRI R. C. J AIN

Deputy Director (Elec tech), ISI






IS : 283 - 1976

3

Indian Standard

SPECIFICATION FOR

PORCELAIN INSULATORS FORTELEGRAPH AND TELEPHONE LINES

( Third Revision )

0. F O R E W O R D

0.1 This Indian Standard (Third Revision) was adopted by the IndianStandards Institution on 2 April 1976, after the draft finalized by theElectrical Insulators and Accessories Sectional Committee had beenapproved by the Electrotechnical Division Council.

0.2 This standard, originally published in 1951, was first revised in1959, when the single-shed pot-head insulators and oil-cup insulatorswere excluded from its scope since the Posts and TelegraphsDepartment of the Government of India had decided to discontinuetheir use. Provision was also made for the inclusion of double-shedpot-head insulators which were found to be satisfactory.

0.2.1 The second revision was issued in 1966 with a view to aligning this standard with other electrical insulator standards and effecting complete metricization. In that revision, which included all theamendments issued to-date to the first revision, a statistical sampling

plan for the selection of insulators for acceptance tests had also beenincorporated.

0.3 The third revision has been undertaken with a view to simplifying the manufacture of large and small double-shed insulators bymodifying the shape of the top of these type of insulators.

0.4 This standard has been prepared primarily to meet therequirements of the Indian Posts and Telegraphs Department. Theinsulators covered by this standard should also be suitable fortelegraph and telephone lines of the Railways and other users. Thestandard does not, however, cover the insulators required for thecommunication circuits run solely for the operation and maintenanceof electric transmission systems and in close proximity to such lines.

0.5 The stalks for use with these insulators are covered byIS : 1441-1966*.

*Specification for insulator stalks for telegraphs and telephone lines ( first revision ).






IS : 283 - 1976

4

0.6 In the preparation of this standard, assistance has been derivedfrom BS 16 : 1949 ‘Telegraph material insulators, pole fittings, etc’issued by British Standards Institution.

0.7 This standard is one of a series of Indian Standard specification onporcelain electrical insulators.

0.8 This edition 4.4 incorporates Amendment No. 1 (October 1983), Amendment No. 2 (March 1989) Amendment No. 3 (October 1991) and Amendment No. 4 (September 2003). Side bar indicates modification of the text as the result of incorporation of the amendments.

0.9 For the purpose of deciding whether a particular requirement of thisstandard is complied with, the final value, observed or calculated,expressing the result of a test, shall be rounded off in accordance withIS : 2-1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

1. SCOPE

1.1 This standard covers the pin type porcelain insulators intendedfor use in supporting telegraph and telephone lines.

1.1.1 This standard does not cover insulators for communication linesrunning in close proximity to power transmission lines.

2. TERMINOLOGY

2.0 For the purpose of this standard, the following definitions shall apply.

2.1 Pin Insulator — A rigid insulator consisting of single piece of

porcelain or of two or more porcelain components permanentlyconnected together, and intended to be mounted rigidly on a supporting structure by an insulator pin passing up inside the insulator. Unlessotherwise stated, this term excludes the insulator pin.

2.2 Lot of Insulator — All the insulators of the same type and designmanufactured under similar conditions of production, offered foracceptance; a lot may consist of the whole or part of the quantity ordered.

2.3 Type Tests — Tests carried out to prove conformity with thespecification. These are intended to prove the general qualities anddesign of a given type of insulator.

2.4 Acceptance Tests — Tests carried out on samples taken from alot for the purpose of acceptance of the lot.

2.5 Routine Tests — Tests carried out on each insulator to checkrequirements which are likely to vary during production.

*Rules for rounding off numerical values ( revised ).






IS : 283 - 1976

5

3. GENERAL REQUIREMENTS

3.1 Material — The porcelain shall be sound, free from defects (suchas cracks, chips, dots, specks, and other imperfections), thoroughly

vitrified and smoothly glazed.

3.2 The glaze shall cover all the porcelain parts of the insulator exceptthose areas which serve as supports during firing or are left unglazedfor the purpose of assembly.

3.3 Colour — Unless specified otherwise by the purchaser, the glazeshall be white in colour.

3.4 Threading — The threads on the insulator shall conform to theprofile shown in Fig. 1.

FIG. 1 PROFILE OF INSULATOR THREADS






IS : 283 - 1976

6

3.4.1 In the case of pot-head insulators, no sealing compound shall beapplied, but the threaded portion of the cap and the corresponding threads on the insulator shall be lightly brushed with pure paraffinwax so as to enable the cap to be easily screwed on and off withoutdamage to the threads.

4. DIMENSIONS

4.1 The shapes and dimensions of insulators shall be in accordancewith the figures referred to against each:

NOTE — Wherever dimensions are not given, the shape of the insulator shallconform to the one indicated in the relevant drawing.

Type Fig. No.

Large, double-shed 2

Small, double-shed 3

Pot-head, double-shed 4

FIG. 2 INSULATOR, L ARGE, DOUBLE-SHED






IS : 283 - 1976

7

5. MARKING

5.1 Each insulator shall be legibly and indelibly marked to show thefollowing:

a) Name or trade-mark of the manufacturer,b) Month and year of manufacture,

c) Country of manufacture, and

d) Minimum failing load in newtons.

5.1.1 Markings on porcelain shall be printed and shall be appliedbefore firing.

5.1.2 The insulators may also be marked with the ISI CertificationMark.

NOTE — The use of the ISI Certification Mark is governed by the provisions of theIndian Standards Institution (Certification Marks) Act and the Rules and

Regulations made thereunder. The ISI Mark on products covered by an IndianStandard conveys the assurance that they have been produced to comply with therequirements of that standard under a well-defined system of inspection, testing and quality control which is devised and supervised by ISI and operated by theproducer. ISI marked products are also continuously checked by ISI for conformityto that standard as a further safeguard. Details of conditions under which a licencefor the use of the ISI Certification Mark may be granted to manufacturers orprocessors, may be obtained from the Indian Standards Institution.

FIG. 3 INSULATOR, SMALL, DOUBLE-SHED






IS : 283 - 1976

8

FIG. 4 INSULATOR, POT-HEAD, DOUBLE-SHED






IS : 283 - 1976

9

6. PACKING

6.1 All insulators shall be packed in layers in a wooden box with cardboard separators fitted with suitable cushion/grass packing on all

inside walls of the box and also between layers if packing consists of more than one layer for the same box.

7. TESTS

7.1 General

7.1.1 Type Tests — The following shall constitute the type tests:

a) Verification of dimensions (7.2),

b) Temperature cycle test (7.3),

c) Insulation resistance test (7.4),

d) Mechanical test (7.5),

e) Porosity test (7.6), and

f) Visual examination (7.7).

7.1.2 Acceptance Tests — The following shall constitute theacceptance tests:

a) Verification of dimensions (7.2),

b) Temperature cycle tests (7.3),

c) Insulation resistance test (7.4),

d) Mechanical test (7.5); and

e) Porosity test (7.6).

7.1.2.1 Unless otherwise agreed, recommended sampling plan givenin Appendix A shall be followed.

NOTE — The sampling plan has been prepared on the basis of IS : 2500 (Part 1) 1973‘Inspection by attributes and by count of defects ( first revision )’, shall provideuniform protection to the supplier of insulators either in small lots or bigger lots.This has been necessitated due to the fact that the earlier criteria of acceptance of lots give less protection to the supplier of smaller lots than the supplier of biggerlots.

7.1.3 The following shall be carried out as routine tests:

a) Routine verification of dimensions (7.2.2),

b) Routine insulation resistance test (7.4.2), and

c) Visual examination (7.7).






IS : 283 - 1976

10

7.2 Verification of Dimensions

7.2.1 The gauges shall be of hardened tool steel and shall be inaccordance with Fig. 5 to 9. They shall he finished bright and all

surfaces shall be protected from oxidation by treatment with neutralpetroleum jelly

7.2.1.1 The insulators shall pass the gauge test as described inTable 1.

7.2.1.2 For dimensions not covered by the gauges a tolerance of ± 5percent shall be allowed. However, the negative tolerance shall not bepermitted for the thickness of the outer shed. The thickness shown inthe figures shall be taken as the minimum permitted. In the case of unimportant dimensions for radii, the tolerances are given for

guidance only and may not be rigidly followed.7.2.2 Routine Verification of Dimensions — In the case of routineverification of dimensions, the insulators shall be tested with the ‘GO’screw gauge ( see Fig. 5 ).

7.3 Temperature Cycle Test

7.3.1 The insulators shall be quickly and completely immersed in awater-bath maintained at a temperature of 70°C above that of the coldwater and left submerged for a period of 15 minutes. They shall thenbe withdrawn and quickly and completely immersed, without being

placed in an intermediate container, in a bath of cold water for thesame period of 15 minutes.

7.3.2 The complete test shall comprise five transfers; namely, hot tocold, cold to hot, hot to cold, cold to hot and hot to cold. The time takento transfer the insulators from one bath to the other shall be as shortas possible and shall not exceed 30 seconds. The quantity of water inthe test tanks shall be large enough not to cause a temperaturevariation of more than 5°C in the water, when the insulators areimmersed.

7.3.3 After the completion of the immersion, the insulator shall beexamined to verify that it is not cracked and the glaze is undamaged.






IS : 283 - 1976

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FIG. 5 ‘GO’ G AUGE






IS : 283 - 1976

12

FIG. 6 TELL-T ALE G AUGE






FIG. 7 G AUGES FOR POT-HEAD INSULATOR C AP






IS : 283 - 1976

14

7.4 Insulation Resistance Test

7.4.1 The insulators shall be kept immersed, as described below,inside an air-conditioned chamber maintained at a constant humidityof 80 ± 2 percent and a temperature of 27 ± 1°C for at least half anhour:

a) Large and small double-shed insulators

1) Method of setting up for test — Level of water in the tank andin the space between sheds shall be 25 mm from the edge of the outer shed. Level of water in the screw-thread cavity shallbe 25 mm below the edge of the inner shed.

FIG. 8 G AUGES FOR POT-HEAD INSULATOR BODY TOP






IS : 283 - 1976

15

2) Test Condition — Insulation to be measured:

i) between water in the inter-shed cavity and the screw-threadcavity, and

ii) between water in the inter-shed cavity and the tank.

FIG. 9 ‘GO’ AND ‘NOT GO’ G AUGES






IS : 283 - 1976

16

b) Pot-head, double-shed insulators:

1) Method of setting up for test — Covers shall be removed beforeimmersion. Level of water in the tank and in the spacebetween sheds shall be 25 mm from the edge of the outer shed.Level of water in the screw-thread cavity shall be 25 mmbelow the edge of the inner shed.

2) Test condition — Insulation to be measured between water in

the inter-shed cavity and the screw-thread cavity.Under the same humidity and temperature conditions, the insulatorsshall be subjected to an insulation resistance test at a dc potential of not less than 250 V and not more than 500 V, measured by a sensitivereflecting galvanometer of D’Arsonval type with a minimumsensitivity of 600 mm per microampere at one metre.

The insulation resistance obtained shall be at least 50 000 megaohms.

7.4.2 Routine Insulation Resistance Test — In the case of routineinsulation resistance test, the insulators shall be completelyimmersed in the inverted position in water for not less than 12 hours.

They shall then be kept immersed in the inverted position in water tothe depths mentioned in 7.4.1 for a period of 4 hours before theinsulation resistance tests are conducted.

7.4.2.1 The insulation resistance shall be measured between pointmentioned in 7.4.1 with a 500-volt, 100 megaohms range insulationtester, and shall not be below the infinity mark, the relative humiditybeing not more than 80 percent.

TABLE 1 GAUGES FOR INSULATORS

( Clause 7.2.1.1 )

G AUGE WHERE USED FIG. NO.

(1) (2) (3)

‘GO’ screw‘TELL-TALE’

For all typesdo

56

‘GO’ plug For cap of pot-head insulatordouble-shed

7‘NOT GO’ plug ‘THREAD’

dodo

‘GO’ ring

‘NOT GO’ ring

For top of body of pot-headinsulator double-shed

do8

‘GO’ tool

‘NOT GO’ tool

For checking the diameter of LS wire-leading in-hole

do9






IS : 283 - 1976

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7.5 Mechanical Test — The insulators shall be mounted on a testpin with a head identical to the one which is used in actual service.The pin shall be fixed upright to a metal bracket on the testing machine. A flexible wire rope, about 6 mm in diameter, shall be loopedround the tie-wire groove and shall be pulled at right angles to theaxis of the insulator. The pull shall be increased gradually and evenlyto the value shown in Table 2 and maintained for one minute. Thereshall be no fracture of the insulator.

7.6 Porosity Test

7.6.1 Porcelain fragments from the insulators shall be immersed inone percent alcoholic solution of fuchsin (1 g fuchsin in 100 g of methylated spirit) under a pressure of not less than 15 MN/m2 for aperiod such that the product of the test duration in hours and the testpressure in MN/m2 is not less than 180.

7.6.2 The fragments shall then be removed from the solution, washed,

dried and broken. Examination with naked eye of the freshly brokensurface shall not reveal any dye penetration. Penetration into smallcracks formed during the initial breaking shall be neglected.

7.7 Visual Examination

7.7.1 A visual examination of the insulator shall be made. Theinsulator shall be free from physical distortion of shape and thevitrified glaze shall be hard and smooth, free from cracks or any otherdefect likely to be prejudicial to satisfactory performance in service.

7.7.2 With the exception of screw threads and those areas [as shown

on the drawings ( see Fig. 2 to 4 )] which serve as supports during firing, the area of unglazed or defectively glazed parts shall not exceed0.25 cm2 per insulator.

7.7.3 The colour of the insulators shall approximate the colourspecified ( see 3.3 ). Some variation in the colour shade is permittedand shall not justify rejection of the insulators.

TABLE 2 TEST LOAD ON INSULATORS

T YPE TEST LOAD TO BE A PPLIED

(1) (2)

kN

Large, double-shed 9Small, double-shed 4.5Pot-head, double-shed 9






IS : 283 - 1976

18

A P P E N D I X A

( Clause 7.1.2.1 )

SAMPLING PROCEDURE FOR PORCELAIN INSULATORSFOR TELEGRAPH AND TELEPHONE LINES

A-1. SCALE OF SAMPLING

A-1.1 Lot — In a consignment, all the insulators of the same type anddesign manufactured from the same material in the same factoryunder similar conditions of production shall be grouped together toconstitute a lot.

A-1.2 The number of insulators to be selected from each lot shalldepend upon the size of the lot and shall be in accordance with col 1

and 2 of Table 3. A-1.2.1 These insulators shall be selected from the lot at random. Inorder to ensure the randomness of selection, procedure given inIS : 4905-1968*, may be followed.

A-2. NUMBER OF TESTS AND CRITERIA FOR CONFORMITY

A-2.1 All the insulators selected at random according to col 1 and 2 of Table 3 shall be subjected to dimensions, temperature cycle andinsulation resistance tests. The insulators failing to satisfy either of the requirements shall be termed as defectives. The lot shall beconsidered as conforming to these requirements if the number of

TABLE 3 SAMPLE SIZE AND ACCEPTANCE NUMBER

( Clauses A-1.2, A-2.1, A-2.2 and A-2.3 )

LOT SIZE FOR DIMENSIONS, TEMPERATURE C YCLE

AND INSULATION RESISTANCE TEST

FOR MECHANICAL

TEST AND

POROSITY TEST

First

SampleSize

Second

SampleSize

Acceptance

Number

First

Rejection( r1 )

Second

Rejection( r2 )

First

SampleSize

Second

SampleSize

(1) (2) (3) (4) (5) (6) (7) (8)

Up to 1 000 8 8 0 2 2 5 5

1 001 to 3 000 13 13 0 2 2 8 8

3 001 to 10 000 20 20 0 2 2 13 13

*Methods for random sampling.






IS : 283 - 1976

19

defectives found in the sample is less than or equal to corresponding acceptance number given in col 4 of Table 3. The lot shall be rejected if the number of defectives in the same is greater than or equal to thefirst rejection number ( r1 ) given in col 5. If the number of defectivesis between the acceptance number and the first rejection number, asecond sample of the same size ( see col 3 of Table 3 ) shall be selectedfrom the lot at random and subjected to these tests. The number of defectives in the first sample and second sample shall be combined. If the combined number of defectives is less than the second rejectionnumber ( r2 ) given in col 6 of Table 3, the lot shall be considered asconforming to these requirements. Otherwise the lot shall be rejectedwithout further testing.

A-2.2 The lot which has been found as conforming to the aboverequirements shall then be divided into two parts, as shown in col 7

and 8 of Table 3. The number of insulators to be tested for mechanicaland porosity tests shall be in accordance with col 7 of Table 3. The lotshall be considered as conforming to these requirements if nodefective is found in the sample and shall be rejected if there are twoor more defectives. If there is one defective, a second sample of samesize ( see col 8 of Table 3 ) shall be selected at random and subjected tothe tests. The lot shall be considered as conforming to theserequirements if no defective is found in the second sample; otherwisethe lot shall be rejected without further testing.

A-2.3 The lot shall be considered as conforming to the requirements of acceptance tests if conditions in A-2.1, and A-2.2 are satisfied.






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Amendments are issued to standards as the need arises on the basis of comments. Standards arealso reviewed periodically; a standard along with amendments is reaffirmed when such reviewindicates that no changes are needed; if the review indicates that changes are needed, it is taken upfor revision. Users of Indian Standards should ascertain that they are in possession of the latestamendments or edition by referring to the latest issue of ‘BIS Catalogue’ and ‘Standards : Monthly Additions’.

This Indian Standard has been developed by Technical Committee : ETDC 3 and amended byETDC 6

Amendments Issued Since Publication

Amend No. Date of Issue Amd. No. 1 October 1983

Amd. No. 2 March 1989

Amd. No. 3 October 1991

Amd. No. 4 September 2003

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VISHAKHAPATNAM

IS-283, Indian Standard for Porcelain Insulator for telegraph and telephone lines.

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