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Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

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“Step Out From the Old to the New”

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“The Right to Information, The Right to Live”

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“Knowledge is such a treasure which cannot be stolen”

“Invent a New India Using Knowledge”

है”ह”ह

IS 9921-3 (1982): Alternating Current Disconnectors(Isolators) and Earthing Switches for Voltages Above 1000V, Part III: Design and Construction [ETD 8: High VoltageSwitchgear and Controlgear]

IS : 9921( Part III) - 1982

Indian Standard

SPECIFICATION FOR ALTERNATING CURRENT DISCONNECTORS (ISOLATORS ) AND

EARTHIHG SWITCHES FOR VOLTAGES ABOVE 1000 V

PART III DESIGN AND CONSTRUCTION

( Second Reprint MARCH 1992 )

UJX 621.316.545.025

Q Copyright 1982

BUREAU OF XNDI’AN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Cr2

L

Sepember 1982

ts t 9821 (Part III) - 1982

Indian Standard

SPECIFICATION FOR ALTERNATING CURRENT ’ -DISCONNECTORS ( ISOLATORS ) AND

EARTHIHG SWITCHES FOR VOLTAGES ABOVE 1000 V

PART III DESIGN AND CONSTRUCTION

High Voltage Switehgear and Controlgear Sectional Committee, ETDC ,58

Chairman

SEBI II. M. PAI Members

Repreanting

The Ahmedabad Electricity Co Ltd, Ahmadabad

SHBI M. B. BAHULEAB ( At&mate to Shri H. M. PAI )

Smtx K. K. Boem Calcutta Electric Supply Corporation Ltd, Calcutta

SEBI T. K. GHOEE ( Alternate ) SHBI R. C~ANDBAXOULI Tata Hydro-Electric Power Supply Co Ltd,

SERIMATI C. BALI~A ( Alternate ) Born bay

DIBEOTO~, S u B - ST A T I o N Central Electricity .Authority, New ~Delhi I)IBEOTOBAT~

DEPUTY DIBEOTOR, SUB-STATION

D~ano::?r~~‘) Central Power Research Institute, B&galore _ - SH~I S. AN~TEA KBI~HNAXU

( Alternate ) SEXI V. JAYAOEANDBAN ( Altemute )

SHSI M. L. DONWE Bombay Electric Supply and Transport Under-

SHBI Y. K. PALVANKA~ ( Alternuh) taking, Bombay

SH~I B. V. E~WAR ASEA, Nalik SHBI S. SUBBAMANI~ ( Alternate )

SHBI K. L. GABO Directorate General of Supplies and Disposals, New Delhi

SHBI R. V. NAILAYA~PAN ( Alternate )

( Continued on page 2 )

BUREAU OF INDIAN STANDARDS’ Thid publioation la protected under the Indian Co&right Act ( XIV of 1957 ) and reproduction in whole or in pert by any meen, except with written permission of the publisher lhall be deemed to be an infringement of copyright under the said Act.

IS :9921( Part In ) - 1982

( Conlinusdfrom pagg 1 )

Mmbns

SHRI B. N. CHOSE

SRI A. RAJA RAO ( Ahmate) SHRI D. K. SINQLE ( Altma:e )

SHBI D. P. GIJPTA

Bharat Heavy Electrical8 Ltd, R & D Unit, Bhopal

Directorate General of Technical Development, New Delhi

SHBI L. GOPALAKBIEOKNAN ( Altmafr ) SHBI JAYAXT N. GVBJA~ Xirloekar-Asea Limited, Bangalore Strax P. D. JAHAQIBDAB Maharashtra State Electricity Board, Bombay SERIJAV~CD AHWED NGEF Limited, Bangalore

SHBI~K. P. SA~ATEY ( Alfrmota) SHBI P. M. JOEWE Aluminium Industries Limited, Kundara

SHBI C. M. A. NAYA~ ( Altarnate ) Sam S. C. KEUBANA Rural Electrification Corporation Ltd, New Delhi

SHRI G. L. DUA ( Altarnats ) Sass B. N. KISHORE Crompton Greavea Ltd, Bombay

SHBI A. N. VENUQOPAL ( Altanats ) SHBI P. C. MALKANI Central Public Works Department, New Delhi

SURVZYO~ OB WORXS III ( Aft&& ) SHBI V. S. MANI Hindu&an Brown Boveri Ltd, Bombay

SHRI S. R. POTNI~ ( Altsrnafr ) SHBI S. G. MENON Tata Consulting Engineer, Bombay

SHRI C. S. KUMAR ( Altnnak ) SHRI S. K. MWHEBJEE ’ National Test House, Calcutta

SHRI P. c. PRAI,EAN ( A&mats ) SHRI B. S. NARASIMEAN Myrore Electrical Industries, Bangalore

SHRI R. SATYANARAYANA ( Altmats ) SHRI JS. NE~I Jyoti Limited, Vadodara

SHRI R. M. NANAVATI ( Alternate ) SHRI S. G. N~WE Siemenr India Ltd, Bombay

SH~I TX. NEELAKANTAN ( Ahnats ) SHRI A. S. PINTO Delhi Electric Supply Undertaking, New Delhi

SH~I S. K. BASU ( Altern&) THIRU T. E. B. SAMUEL Tamil Nadu Electricity Board, Madras

TEIRU T. SHEMBAHABAJAN ( Utmurb) SHRI S. P. SAOHDEV, Director General, IS1 ( Ex-o&io Mmnbev )

Director ( Elec tech )

SH~I K. GANES= Assistant Director ( Elec tech ), IS1

2

IS : 9921 ( Rart III ) - 1982

Indian Standard SPECIFICATION FOR ALTERNATING CURRENT

DISCONNECTORS (ISOLATORS) AND EARTHING SWITCHES -FOR

VOLTAGES ABOVE 1 OOd V

PART III DESIGN AND CONSTRUCTION

0. FOREWORD

0.1 This Indian ‘Standard (Part III ) was adopted by the Indian Standards Institution on 26 May 1982, after the draft finalized by the High Voltage Switchgear and Controlgear Sectional Committee had been approved by the Electrotechnical Division Council.

0.2 With the large scale manufacture of air-break isolators in India, the need for specifying uniform requirements of such equipment was felt particularly in view of different practices being followed by the manu- facturers because of their tie-ups with different overseas manufacturers. This standard was, therefore, originally prepared as IS : 1818 in 196 1 to meet this need and to provide guidance to the new manufacturers in this field,

0.3 The first revision of IS : 1818 was brought out in 1972, mainly for the purposes of taking into account the rdevelopments at the international level, as well as to expand the scope to cover ratings up to 420 kV. The revision, in comparison to the original version, also covered oil-break type isolators and earthing switches; the latter considered similar in operation to the former, The revision, however, recognized the fact that when both the isolators and earthing switches are combined in one unit, an interlock is needed to be provided to ensure proper operation and safety.

0.4 During the last few years, in the development of high voltage switch- gear there had been considerable advancement in knowhow on the per- formance of the equipment and the associated stipulations that are to be precisely made in the national standards. Considerable modifications were, therefore, made necessary in the specifications on circuit breakers, switches, fuses, etc,-in order to keep pace with the international thinking on the subject.

3

ISr9921(PartIIn)-1982

0.5 The present version of the standard on the subject is, therefore, being brought out to incorporate the latest in technology as is also recognized in the international field. For the purposes of clarity, this standard is being brought out in five parts as follows:

Part I

Part II

Part III

Part IV

Part V

General and definitions,

Rating,

Design and construction,

Type tests and routine tests ( U&Y @$~~rutiun ), and

Information to be given with tenders, enquiries and orders and rules for selection, transport, erection and main- tenance ( under pre$~rution ).

All parts shall be read in conjunction with one another. This standard ( Part III ) dealing with design and constructional aspects partly replaces IS : 1818-1972*. All parts of this standard when published shall replace IS : 18 18 completely.

0.6 While preparing this standard, assistance has been derived from IEC Pub 129-1975 ‘ Alternating current discormectors (isolators ) and earthing switches ’ published by the International Electrotechnical Commission.

0.7 In order to facilitate comparison with the international standards and for ease of reference, the committee responsible for the Preparation of this standard has decided to add in the form of an appendix, the major differences between this Indian Standard and. the corresponding IEC Publication. This standard ( Part III ) conforms appreciably to the IEC Publication referred to in 0.6 and there are no major deviations.

0.8 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS : 2-19607. 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 ( Part III ) -coven the design and constructional features of isolators and earthing switches intended for use on system voltages above I 000 V ac.

NOTBI - For detailed scope of this terier of rtandards, on higb voltage ac isolators and earthing switches w 1 of Part I of this stand&.

*Spe+cation for alternating CUrrent ismktor~ ( disconnectora) and emtbingmvitchas ( jirst remwn ) .

tRu1e.q for rounding off numerical valuea ( rtpirud ).

4

2. TERMINOLOGY

2.1 For the purpose of this standard ( Part III ), the definitions given in 4.1 of Part I of this standard shall apply.

3. REQUIREMENTS FOR LIQUIDS AND GASES IN DISCONNECTORSAND EART@ING SWITCHES

3.1 Liquid Level

3.1.1 It shall be possible to fill and drain liquid-filled disconnectors and earthing switches easily. A device for checking the liquid level, even during service, with indication of minimurp and maximuin limits admissi- ble for correct operation shall be provided%

3.2 Li+d Quality

3.2.1 Liquid for use in liquid-filled disconnectors or caxthing switcheu shall comply with the instructions of the manufacturer ( SW also IS : 335 - 197!?).

3.3 Gases

3.3.1 The manufacturer shall specify the type and the required quantity and quality of the gas to be used in a disconnector or earthing switch-and provide the user with necessary instructions for renewing the gas and maintaining its required quality. (An Indian Standard specification for gases in switchgear.is under consideration. )

4. SPECIAL REQUIREMENTS FOR EARTHING, SWITCHES

4.1 Flexible connections between the earthing blade and the frame shtill have a cross-section of at least 51) mms copper or equivalent ira ahnninium.

NATE - The minimum vdue of-the crowsectional are8 of dapper connectiona is given to ensure mechanical strength and resistance to corrosion.

h REQUIREMENTS IN RESPECT OF THE ISOEATBNG DISTANCE OF DISCONNECTORS

5.1 For reasons of safety, disconnectors.should be ao designed that f10 dangerous leakage currents can,pass from the terminals of one side to any of the terminals of the other side of the disconnector.

This safety requirement is met when any leakage.currcnt is.kd a-y to earth by a reliable -earth connection or when the insulation involved is effectively protected against pollution in servicet.

*Specification for new insulating oils for ttanaform&rr and 8wirchgear (A tWision ) .

*Tests to prove the effectiveneaa of the protection againrt pollution and t4e perfor- mance of insulation material io respect of le&age cutteotr.are u8drC conder*on.

5

IS I !w21( Part III ) - 1982

NOTE - For disconnectors which contai a dielectric other than air at atmos- pheric pressure, the dielectric conditions to % e specified for the isolating distance may form the subject of agreement between the manufacturer and the user.

6. EARTHING OF DISCONNECTORS AND EARTHING SWITCHES

6.1 The frame of each disconnector and earthing switch shall be provided with a reliable earthing terminal for connection to an earthing conductor having a clamping screw, suitable for specified earth fault conditions. The diameter of the clamping screw shall be at least. 12 mm. The connecting point shall be marked with the ‘ earth ’ symbol.

7. MECHANICAL STRENGTH

7.1 Disconnectors or earthing switches when installed according to the manufacturer’s instructions shall be able to bear on the terminals the total forces ( including wind loading and electrodynamic forces -on the attached conductors ) related to the ~application and rating without impairing their reliability or current-carrying capacity.

8. POSITION OF THE MOVABLE CONTACT SYSTEM AND ITS INDICATING OR SIGNALLING DEVICES

8.1 Securing of Position

8.1.1 Disconnectors and earthing switches, including their operating mechanisms, shall be so constructed that they cannot come out of their open or closed positions by gravity, wind pressure, vibrations, reasonable shocks or accidental touching of the connecting rods of their operating mechanism.

8.1.2 Rand-operated disconnectors and earthing switches shall be SO constructed as to permit locking in both the open and closed positions only.

NOTE 1 -This applies also to the emergency hand-operated devices of auto- matically 0~ retiotely controlled disconnectors and earthing switches.

NOTE 2 -These requirements need not be met in the case of disconnectors or earthing switches which are operated by means of a hook-stick.

8.1.3 Automatically or remotely controlled disconnectors and earthing switches may be so constructed as to permit locking both in the open and the closed positions.

8.2 Indication of Position

8.211 It shall be possible to know the operating position of the discon- nector or earthing switch. This requirement is met if one of the following conditions is fulfilled:

a) the isolating distance or gap is visible, and

6

rs : 9921( Part m ) - 1982

b) the position of each movable contact ensuring the isolating distance or gap is indicated ~by a reliable position-indicating device.

NOTE 1 - Visible moving contacts may serve as the indicating devices.

NOTE 2 - In the case where all poles of a disconnector or earthing switch are so coupled as to be operable as a single utlit, it is permissible to use a common indicating device.

NOTE 3 - For equipment of which the insulating medium is other than air at atmospheric pressure, special requirements will be a subject for study.

8.3 Auxiliary Cdntacte for Signal&g

8.3.1 Signalling of the closed position shal! not take place unless it is certain that the movable contacts will reach a position in which the rated normal current, the peak withstand current and the short-time withstand current can be carried safely.

8.3.2 Signalling of the open position shall not take place unless the movable contacts have reached a position such that the clearance between contacts is at least 80 percent of the gap or the isolating distance, or unless it is certain that the movable contacts will reach their fully open position.

8.3.3 k common signalling device for all poles of disconnector or earthing switch shall be arranged in such a way that the signal is given only in the case of all poles of the disconnector or earthing switch having a position in accordance with 8.3.1 or 8.3.2.

NOTE 1 - In the case where all poles of a disconnector or earthing switch are so coupled as to Abe operable as a single unit, it is permisaible to use a common position- signalling device.

NOTE 2- Upon special request, rignailing of the open position of a disconnector shall not take place until all the movable contacts ,have reached a stable open condition as defined in 8.1.1.

-9. AUXILIARY EQUIPMENT

9.1 Auxiliary switches and auxiliary circuits shall be capable bf carrying a current of at least 10 A continuously. Permissible temperature rises shall be in accordance with Table 4 of Part II of this standard.

9.2 Auxiliary switches shall be capable of breaking the current of the circuits to be controlled, particulars of which should be specified to the manufacturer. In thi absence of such a specification, they shall be capable of breaking at least 2 A at 220 V dc with a circuit time-constant of not less than 20 milliieeonds.

7

r8:992i(Pmtm)-l!M?2

Auxilizky switches sha;ll be positively driven in both directions.

9.3 Auxiliary switches which are installed on the frame of disconnectors or earthing switches shall be suitably protected against accidental arcing from the main circuit.

9.4 The insulating materials of autiliary switches and terminals of auxiliary circuits which are to be used under outdoor conditidns shall be non-tracking and non-hygroscopic.