BS-IEC-61363-1-1998.pdf

BRITISH STANDARD BS IEC 61363-1:1998 Electrical installations of ships and mobile and fixed offshore units Part 1: Procedures for calculating short-circuit currents in three-phase a.c. ICS 47.020.60 ? Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS IEC 61363-1:1998 This British Standard, having been prepared under the direction of the Electrotechnical Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 14 August 2002 © BSI 14 August 2002 ISBN 0 580 40254 1 National foreword This British Standard reproduces verbatim IEC 61363-1:1998 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee JPEL/18, Electrical installations of ships and of mobile and fixed offshore units, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the IEC title page, pages 2 to 41 and the back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 61363-1 Première édition First edition 1998-02 Installations électriques à bord des navires et des plates-formes mobiles et fixes en mer Partie 1: Evaluation des courants de court-circuit en c.a. triphasé Electrical installations of ships and mobile and fixed offshore units Part 1: Procedures for calculating short-circuit currents in three-phase a.c. Numéro de référence Reference number CEI/IEC 61363-1:1998 BS IEC 613631:1998 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI CONTENTS Page FOREWORD 4 Clause 1 Scope and object 5 2 Normative references .6 3 Definitions, symbols, subscripts and superscripts .6 3.1 Definitions 6 3.2 Symbols . 9 3.3 Subscripts .12 3.4 Superscripts .12 4 Introductory information .12 4.1 General .12 4.2 Calculation accuracy 13 4.3 Basic assumptions .13 4.4 Calculation methods .14 5 System components and models .15 5.1 Active components15 5.2 Non-active components 24 6 Simplifying assumptions 25 6.1 General 25 6.2 Synchronous machines 25 6.3 Asynchronous motors .27 7 Application of the equivalent generator .29 7.1 General 29 7.2 Assumptions .29 7.3 Evaluation of the equivalent motor29 7.4 Evaluation of the equivalent generator30 8 System calculations .33 8.1 General 33 8.2 Effects of non-active components connected in series with active components .33 8.3 Short-circuit current at the generator busbars 34 BS IEC 613631:1998 2 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ClausePage 8.4 Short-circuit currents at secondary busses directly connected to the generator bus .35 8.5 Transformers 36 8.6 Semi-conductor converters used on variable speed drives 36 8.7 Calculation procedures 37 9 Interpretation and application of the results .39 BS IEC 613631:1998 3 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI -363168991:CEI © 1 7 INTERNATIONAL ELECTROTECHNICAL COMMISSION ELECTRICAL INSTALLATIONS OF SHIPS AND MOBILE AND FIXED OFFSHORE UNITS Part 1: Procedures for calculating short-circuit currents in three-phase a.c. FOREWORD 1)The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2)The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested National Committees. 3)The documents produced have the form of recommendations for international use and are published in the form of standards, technical reports or guides and they are accepted by the National Committees in that sense. 4)In order to promote international unification, IEC National Committees undertake to apply IEC International Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 5)The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with one of its standards. 6)Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights. This part of International Standard IEC 61363 has been prepared by IEC technical committee 18: Electrical installations of ships and of mobile and fixed offshore units. This standard cancels and replaces IEC 60363, published in 1972. The text of this standard is based on the following documents: FDISReport on voting 18/831/FDIS18/837/RVD Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. BS IEC 613631:1998 4 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI -363168991:CEI © 1 9 ELECTRICAL INSTALLATIONS OF SHIPS AND MOBILE AND FIXED OFFSHORE UNITS Part 1: Procedures for calculating short-circuit currents in three-phase a.c. 1 Scope and object This International Standard outlines procedures for calculating short-circuit currents that may occur on a marine or offshore a.c. electrical installation. The calculation methods are for use on unmeshed three-phase alternating current systems, a) operating at 50 Hz or 60 Hz; b) having any system voltage specified in IEC 60092-201 table 2; c) having one or more different voltage levels; d) comprising generators, motors (both synchronous and asynchronous), transformers, reactor coils, cables, and converter units; e) having their neutral point connected to the ships hull through an impedance (designed to limit the short-circuit current flowing to the ships hull); f) having their neutral point isolated from the ships hull. The calculation procedures are for a three-phase symmetrical short-circuit condition i.e. three- phase conductors shorted together, or shorted to the ships hull and for which the short-circuit occurs on all three poles simultaneously. The calculation of short-circuit currents resulting from asymmetric short-circuit conditions can lead to higher aperiodic (d.c.) components of the short- circuit current and is not considered in this standard. The calculating formulae and methods described produce sufficiently accurate results to calculate the short-circuit current during the first 100 ms of a fault condition. They can be used to calculate the short-circuit current for periods longer than 100 ms when calculating on a bus system to which the generators are directly connected. For time periods beyond 100 ms the controlling effects of the system voltage regulators may be predominant. Calculations including the voltage regulator effects are not considered in this standard. The object of this standard is to present formulae for calculating short-circuit currents of the active components of an electrical system and to indicate how such formulae may be simplified when calculating the short-circuit current at various locations on the electrical system. The calculations give estimates of the prospective short-circuit current when the systems active components produce their maximum contribution. The calculating formulae are developed from basic electrical engineering theories relevant to the system components. To simplify the calculation methods yet retain an acceptable level of accuracy in the results, suitable assumptions are outlined and their effects on the calculation results indicated. This standard provides a calculation procedure. It gives guidance on the interpretation and application of simplifying formulae and the corresponding results when applied to the selection of switchgear. The standard is not intended to provide any other information other than the calculation of the short-circuit current which may flow in the network. BS IEC 613631:1998 5 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI -363168991:CEI © 1 11 In order to understand the methods, and consequences of the results, it is assumed that the person responsible for initiating the short-circuit current calculations, is thoroughly familiar with valid electrical engineering fundamentals. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 60034-4:1985, Rotating electrical machines Part 4: Methods for determining synchronous machine quantities from tests IEC 60038:1983, IEC standard voltages IEC 60050(151):1978, International Electrotechnical Vocabulary (IEV) Chapter 151: Electrical and magnetic devices IEC 60050(411):1996, International Electrotechnical Vocabulary (IEV) Chapter 411: Rotating machinery IEC 60050(441):1984, International Electrotechnical Vocabulary (IEV) Chapter 441: Switchgear, controlgear and fuses IEC 60092-201:1994, Electrical installations in ships Part 201: System design General IEC 60092-202:1994, Electrical installations in ships Part 202: System design Protection IEC 60909:1988, Short-circuit current calculation in three-phase a.c. systems 3 Definitions, symbols, subscripts and superscripts 3.1 Definitions For the purpose of this International Standard the following definitions and symbols apply. 3.1.1 short circuit accidental or intentional connection, by a relatively low resistance or impedance, of two or more points in a circuit which are normally at different voltages. IEV 151-03-41 3.1.2 short-circuit current over-current resulting from a short circuit due to a fault or an incorrect connection in an electric circuit. IEV 441-11-07 BS IEC 613631:1998 6 Licensed Copy: sheffieldun sheffieldun, na, Sun Nov 26 14:31:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI -363168991:CEI © 1 31 3.1.3 prospective current (with respect to a switching device) short-circuit current that would flow in the circuit if each pole of the device were replaced by a conductor of negligible impedance. IEV 441-17-01, modified 3.1.4 symmetrical short-circuit current r.m.s. value of the a.c. symmetrical component of a prospective (available) short-circuit current, the aperiodic component of current, if any, being neglected. (IEC 60909, subclause 3.4) 3.1.5 initial symmetrical short-circuit current I“k r.m.s. value of the a.c. symmetrical component of a prospective (available) short-circuit current applicable at the instant of short circuit if the impedance remains at zero-time value. (3.5 of IEC 60909, see also figure 2). 3.1.6 subtransient short-circuit current I“kd in the direct axis r.m.s. value of the short-circuit current flowing through a circuit with rotating machine(s) having an impedance (reactance) equal to the subtransient impedance (reactance) of the circuit. 3.1.7 transient short-circuit current I'kd in the direct axis r.m.s. value of the short-circuit current flowing through a circuit with rotating machine(s) having an impedance (reactance) equal to the transient impedance (reactance) of the circuit. 3.1.8 steady-state short-circuit current Ikd in the direct axis r.m.s. value of the short-circuit symmetrical current flowing through a circuit with generator(s) which remains after the decay of the transient phenomena. 3.1.9 aperiodic (d.c.) component of the short-circuit current idc component of current in a circuit immediately after it has been suddenly short-circuited, all components of fundamental and higher frequencies being excluded. NOTE It is the mean value between the top and bottom envelope of a short-circuit current decaying from an initial value A to zero according to figure 2. 3.1.10 peak short-circuit current ip maximum possible instantaneous value of the prospective (available) short-circuit current (see figure 2 and 3.8 of IEC 60909). NOTE For three-phase short circuits it is assumed that the short circuit occurs simultaneously in all phase conductors. 3.1.11 direct-axis subtransient short-circuit time constant T“d time required for the rapidly changing component, present during the first few cycles in the direct-axis short-circuit current following a sudden change in operating conditions, to decrease to 1/e, i.e. 0,368 of its initial value, the mac