इंटरनेट मानक Disclosure to Promote the Right To Information 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. “जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New” IS/IEC 60071-1 (2006): Insulation Co-ordination, Part 1: Definitions, Principles and Rules [ETD 19: High Voltage Engineering] “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda ““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee”” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” IS/IEC 60071-1 : 2006 [Superseding IS 2165 (Part 1) : 1977] Hkkjrh; ekud Å"ekjkès ku leUo;u Hkkx 1 ifjHkk"kk] fl¼kar vkSj fu;e Indian Standard INSULATION CO-ORDINATION PART 1 DEFINITIONS, PRINCIPLES AND RULES ICS 29.080.30 © BIS 2012 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 September 2012 Price Group 12 High Voltage Engineering Sectional Committee, ETD 19 NATIONAL FOREWORD This Indian Standard (Part 1) which is identical with IEC 60071-1 : 2006 ‘Insulation co-ordination — Part 1: Definitions, principles and rules’ issued by the International Electrotechnical Commission (IEC) was adopted by the Bureau of Indian Standards on the recommendation of the High Voltage Engineering Sectional Committee and approval of the Electrotechnical Division Council. This standard was earlier published as IS 2165 (Part 1) : 1977 ‘Insulation coordination: Part 1 Phase to earth insulation coordination principles and rules (second revision)’. The Committee has decided to adopt this standard in a single number as IS/IEC, based on IEC 60071-1 : 2006. This standard supersedes IS 2165 (Part 1) : 1977. After the publication of this standard IS 2165 (Part1) : 1977 shall be treated as withdrawn. The text of IEC Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following: a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’. b) Comma (,) has been used as a decimal marker, while in Indian Standards the current practice is to use a point (.) as the decimal marker. In this adopted standard, references appear to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards, which are to be substituted in their respective places are listed below along with their degree of equivalence for the editions indicated: International Standard Corresponding Indian Standard Degree of Equivalence IEC 60038 : 2002 IEC standard IS 12360 : 1988 Voltage bands for Technically Equivalent voltages electrical installations including preferred voltages and frequency IEC 60060-1 : 1989 High-voltage test IS 2071(Part 1) : 1993 High-voltage Identical techniques — Part 1: General test techniques: Part 1 General definitions and test requirements definitions and test requirements (second revision) IEC 60071-2 Insulation co-ordination IS/IEC 60071-2 : 1996 Insulation co- Identical with — Part 2: Application guide ordination: Part 2 Application guide IEC 60071-2 : 1996 IEC 60099-4 Surge arresters — IS 3070 (Part 3) : 1993 Lightning Technically Equivalent Part4: Metal-oxide surge arresters arresters for alternating current without gaps for a.c. systems systems – Specification: Part 3 Metal oxide lightning arresters without gaps for a.c. systems IEC 60507 Artificial pollution test on IS 8704 : 1995 Artificial pollution Identical with high-voltage insulators to be used on test on high-voltage insulators to be IEC 60507 : 1991 a.c. systems used on a.c. systems (first revision) IEC 60633 Terminology for high- IS 14801 : 2000 Terminology for Identical with voltage direct current (HVDC) high-voltage direct current (HVDC) IEC 60633 : 1998 transmission transmission (Continued on third cover) IS/IEC 60071-1 : 2006 Indian Standard INSULATION CO-ORDINATION PART 1 DEFINITIONS, P RINCIPLES AND RULES 1 Scope This part of IEC 60071 applies to three-phase a.c. systems having a highest voltage for equipment above 1 kV. It specifies the procedure for the selection of the rated withstand voltages for the phase-to-earth, phase-to-phase and longitudinal insulation of the equipment and the installations of these systems. It also gives the lists of the standard withstand voltages from which the rated withstand voltages should be selected. This standard recommends that the selected withstand voltages should be associated with the highest voltage for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this standard. Although the principles of this standard also apply to transmission line insulation, the values of their withstand voltages may be different from the standard rated withstand voltages. The apparatus committees are responsible for specifying the rated withstand voltages and the test procedures suitable for the relevant equipment taking into consideration the recommendations of this standard. NOTE In IEC 60071-2, Application Guide, all rules for insulation co-ordination given in this standard are justified in detail, in particular the association of the standard rated withstand voltages with the highest voltage for equipment. When more than one set of standard rated withstand voltages is associated with the same highest voltage for equipment, guidance is provided for the selection of the most suitable set. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60038:2002, IEC standard voltages IEC 60060-1:1989, High-voltage test techniques – Part 1: General definitions and test requirements IEC 60071-2, Insulation co-ordination – Part 2: Application guide IEC 60099-4, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c. systems IEC 60507, Artificial pollution tests on high-voltage insulators to be used on a.c. systems IEC 60633, Terminology for high-voltage direct current (HVDC) transmission 1 IS/IEC 60071-1 : 2006 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 insulation co-ordination selection of the dielectric strength of equipment in relation to the operating voltages and overvoltages which can appear on the system for which the equipment is intended and taking into account the service environment and the characteristics of the available preventing and protective devices [IEC 604-03-08:1987, modified] NOTE By "dielectric strength" of the equipment, is meant here its rated or its standard insulation level as defined in 3.35 and 3.36 respectively. 3.2 external insulation distances in atmospheric air, and the surfaces in contact with atmospheric air of solid insulation of the equipment which are subject to dielectric stresses and to the effects of atmospheric and other environmental conditions from the site, such as pollution, humidity, vermin, etc. [IEC 604-03-02:1987, modified] NOTE External insulation is either weather protected or non-weather protected, designed to operate inside or outside closed shelters respectively. 3.3 internal insulation internal distances of the solid, liquid, or gaseous insulation of equipment which are protected from the effects of atmospheric and other external conditions [IEC 604-03-03:1987] 3.4 self-restoring insulation insulation which, after a short time, completely recovers its insulating properties after a disruptive discharge during test [IEC 604-03-04:1987, modified] NOTE Insulation of this kind is generally, but not necessary, external insulation 3.5 non self-restoring insulation insulation which loses its insulating properties, or does not recover them completely, after a disruptive discharge during test [IEC 604-03-05:1987, modified] NOTE The definitions of 3.4 and 3.5 apply only when the discharge is caused by the application of a test voltage during a dielectric test. However, discharges occurring in service may cause a self-restoring insulation to lose partially or completely its original insulating properties. 3.6 insulation configuration terminal any of the terminals between any two of which a voltage that stresses the insulation can be applied. The types of terminal are: (a) phase terminal, between which and the neutral is applied in service the phase-to-neutral voltage of the system; (b) neutral terminal, representing, or connected to, the neutral point of the system (neutral terminal of transformers, etc.); (c) earth terminal, always solidly connected to earth in service (tank of transformers, base of disconnectors, structures of towers, ground plane, etc.). 2 IS/IEC 60071-1 : 2006 3.7 insulation configuration complete geometric configuration of the insulation in service, consisting of the insulation and of all terminals. It includes all elements (insulating and conducting) which influence its dielectric behaviour. The following insulation configurations are identified: 3.7.1 three-phase insulation configuration configuration having three phase terminals, one neutral terminal and one earth terminal 3.7.2 phase-to-earth (p-e) insulation configuration three-phase insulation configuration where two phase terminals are disregarded and, except in particular cases, the neutral terminal is earthed 3.7.3 phase-to-phase(p-p) insulation configuration three-phase insulation configuration where one phase terminal is disregarded. In particular cases, the neutral and the earth terminals are also disregarded 3.7.4 longitudinal(t-t) insulation configuration insulation configuration having two phase terminals and one earth terminal. The phase terminals belong to the same phase of a three-phase system temporarily separated into two independently energized parts (e.g. open switching devices). The four terminals belonging to the other two phases are disregarded or earthed. In particular cases one of the two phase terminals considered is earthed 3.8 nominal voltage of a system U n suitable approximate value of voltage used to designate or identify a system [IEC 601-01-21:1985] 3.9 highest voltage of a system U s highest value of the phase-to-phase operating voltage (r.m.s. value) which occurs under normal operating conditions at any time and at any point in the system [IEC 601-01-23:1985, modified] 3.10 highest voltage for equipment U m highest value of phase-to-phase voltage (r.m.s. value) for which the equipment is designed in respect of its insulation as well as other characteristics which relate to this voltage in the relevant equipment Standards. Under normal service conditions specified by the relevant apparatus committee this voltage can be applied continuously to the equipment [IEC 604-03-01:1987, modified] 3 IS/IEC 60071-1 : 2006 3.11 isolated neutral system system where the neutral point is not intentionally connected to earth, except for high impedance connections for protection or measurement purposes [IEC 601-02-24:1985] 3.12 solidly earthed neutral system system whose neutral point(s) is(are) earthed directly [IEC 601-02-25:1985] 3.13 impedance earthed (neutral) system system whose neutral point(s) is(are) earthed through impedances to limit earth fault currents [IEC 601-02-26:1985] 3.14 resonant earthed (neutral) system system in which one or more neutral points are connected to earth through reactances which approximately compensate the capacitive component of a single-phase-to-earth fault current [IEC 601-02-27:1985] NOTE With resonant earthing of a system, the residual current in the fault is limited to such an extent that an arcing fault in air is usually self-extinguishing. 3.15 earth fault factor k at a given location of a three-phase system, and for a given system configuration, the ratio of the highest r.m.s. phase-to-earth power frequency voltage on a healthy phase during a fault to earth affecting one or more phases at any point on the system to the r.m.s. phase-to-earth power frequency voltage which would be obtained at the given location in the absence of any such fault [IEC 604-03-06:1987] 3.16 overvoltage any voltage: – between one phase conductor and earth or across a longitudinal insulation having a peak value exceeding the peak of the highest voltage of the system divided by 3 ; [IEC 604-03-09, modified] or – between phase conductors having a peak value exceeding the amplitude of the highest voltage of the system [IEC 604-03-09:1987, modified] NOTE Unless otherwise clearly indicated, such as for surge arresters, overvoltage values expressed in p.u. refer to U × 2 3 s 4 IS/IEC 60071-1 : 2006 3.17 classification of voltages and overvoltages according to their shape and duration, voltages and overvoltages are divided in the following classes NOTE More details on the following six first voltages and overvoltages are also given in Table 1. 3.17.1 continuous (power frequency) voltage power-frequency voltage, considered having constant r.m.s. value, continuously applied to any pair of terminals of an insulation configuration 3.17.2 temporary overvoltage TOV power frequency overvoltage of relatively long duration [IEC 604-03-12:1987, modified] NOTE The overvoltage may be undamped or weakly damped. In some cases its frequency may be several times smaller or higher than power frequency. 3.17.3 transient overvoltage short-duration overvoltage of few milliseconds or less, oscillatory or non-oscillatory, usually highly damped [IEC 604-03-13:1987] NOTE Transient overvoltages may be immediately followed by temporary overvoltages. In such cases the two overvoltages are considered as separate events. Transient overvoltages are divided into: 3.17.3.1 slow-front overvoltage SFO transient overvoltage, usually unidirectional, with time to peak 20 µs < T ≤ 5 000 µs, and tail p duration T ≤ 20 ms 2 3.17.3.2 fast-front overvoltage FFO transient overvoltage, usually unidirectional, with time to peak 0,1 µs < T ≤ 20 µs, and tail 1 duration T < 300 µs 2 3.17.3.3 very-fast-front overvoltage VFFO transient overvoltage, usually unidirectional with time to peak T ≤ 0,1 µs, and with or without f superimposed oscillations at frequency 30 kHz < f < 100 MHz 3.17.4 combined overvoltage consisting of two voltage components simultaneously applied between each of the two phase terminals of a phase-to-phase (or longitudinal) insulation and earth. It is classified by the component of higher peak value (temporary, slow-front, fast-front or very-fast-front) 5