• IEC 60781:1989

    Withdrawn A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.

    Application guide for calculation of short-circuit currents in low-voltage radial systems

    Available format(s):  Hardcopy, PDF, PDF 3 Users, PDF 5 Users, PDF 9 Users

    Withdrawn date:  31-12-2021

    Language(s):  English - French

    Published date:  30-01-1989

    Publisher:  International Electrotechnical Committee

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    Table of Contents - (Show below) - (Hide below)

    1 Scope
    2 Object
    3 General calculation methods and calculation assumptions
    4 Definitions
       4.1 Short circuit
       4.2 Far-from-generator short circuit
       4.3 Short-circuit current
       4.4 Prospective (available) short-circuit current
       4.5 Initial symmetrical short-circuit current
       4.6 Peak short-circuit current
       4.7 Symmetrical short-circuit breaking current
       4.8 Steady-state short-circuit current
       4.9 Nominal system voltage
       4.10 Short-circuit impedances of electrical equipment
       4.11 Short-circuit impedances at the short-circuit location
       4.12 Voltage source
       4.13 Equivalent voltage source
       4.14 Voltage factor c
    5 Symbols, subscripts and superscripts
       5.1 Symbols
       5.2 Subscripts
       5.3 Superscripts
    6 Short-circuit types
    7 Calculation methods and assumptions
       7.1 Symmetrical components
       7.2 Equivalent voltage source at short-circuit location
       7.3 Conditions for disregarding the influence of motors
    8 Short-circuit impedances of electrical equipment
       8.1 High-voltage network feeders
       8.2 Transformers
       8.3 Overhead lines and cables
       8.4 Other impedance elements
       8.5 Conversion of impedances
    9 Calculation of short-circuit currents
       9.1 Balanced three-phase short-circuit current
       9.2 Line-to-line short-circuit current without earth
       9.3 Line-to-earth short-circuit current
    10 Example of short-circuit current calculations using forms
       10.1 General procedure
       10.2 Explanations for using the calculation forms
    11 Example for a housing installation
       11.1 Network diagram
       11.2 Data of electrical equipment
       11.3 Special remarks

    Abstract - (Show below) - (Hide below)

    This application guide presents a practical method to be used when calculating short-circuit currents in low-voltage networks. The method corresponds strictly with IEC 60909 and leads to conservative results with sufficient accuracy.Two short-circuit currents which differ in magnitude are to be calculated:-the maximum short-circuit current which causes the maximum thermal and electromagnetic effects on electrical equipment and determines the required capacity or rating;-the minimum short-circuit current which may be a basis for the adjustment of protective devices.

    General Product Information - (Show below) - (Hide below)

    Development Note Also numbered as BS 7638(1993) (10/2005)
    Document Type Standard
    Publisher International Electrotechnical Committee
    Status Withdrawn

    Standards Referenced By This Book - (Show below) - (Hide below)

    C22.1-15 PACKAGE Consists of C22.1-15, Canadian electrical code, part I (23rd edition), safety standard for electrical installations; C22.1HB-15, Canadian electrical code handbook - an explanation of rules of the Canadian electrical code, part I and the 2015 Electrical quick reference
    C22.1HB-18 Canadian Electrical Code Handbook - An Explanation of the Rules of the Canadian Electrical Code, Part I
    C22.10-10 Québec Construction Code, Chapter V - Electricity Canadian Electrical Code, Part I (Twenty-first Edition) with Québec Amendments
    C22.1-18 Canadian Electrical Code, Part I (24th Edition), Safety Standard for Electrical Installations

    Standards Referencing This Book - (Show below) - (Hide below)

    IEC 60038:2009 IEC standard voltages
    IEC 60050-131:2002 International Electrotechnical Vocabulary (IEV) - Part 131: Circuit theory
    IEC 60050-151:2001 International Electrotechnical Vocabulary (IEV) - Part 151: Electrical and magnetic devices
    IEC 60050-441:1984 International Electrotechnical Vocabulary (IEV) - Part 441: Switchgear, controlgear and fuses
    IEC 60909:1988 Short-circuit current calculation in three-phase a.c. systems
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