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AS 3851-1991
[Current]The calculation of short-circuit currents in three-phase a.c. systems
Specifies standard methods for the calculation of short-circuit currents in three-phase a.c. systems, both radial and meshed with and without contribution from generators and motors, which are suitable for either computer or manual calculation.
Published: 13/05/1991
Pages: 88
Table of contents
Cited references
Content history
Table of contents
Header
About this publication
PREFACE
FOREWORD
1 SCOPE AND GENERAL
1.1 Scope
1.2 Referenced documents
1.3 Definitions
2 NOTATION
2.1 General
2.2 Quantity symbols
3 CHARACTERISTICS OF SHORT-CIRCUIT CURRENTS
4 OUTLINE OF METHOD OF CALCULATION
4.1 General
4.2 Assumptions
4.3 Method of calculation
4.4 Conversion of impedances, currents and voltages
5 MAXIMUM AND MINIMUM SHORT-CIRCUIT CURRENTS
5.1 General
5.2 Maximum short-circuit currents
5.3 Minimum short-circuit currents
6 METHOD OF SYMMETRICAL COMPONENTS
6.1 General
6.2 Short-circuit impedances at the short-circuit location (F)
7 IMPEDANCES, REACTANCES AND RESISTANCES OF ELECTRICAL EQUIPMENT
7.1 General
7.2 Source networks
7.3 Transformers
7.4 Cables and overhead lines
7.5 Synchronous motors and compensators
7.6 Asynchronous motors
7.7 Static converter fed drives
7.8 Synchronous generators
7.8.1 General
7.8.2 Generators connected to systems through transformers
7.9 Series reactors
7.10 Series capacitors
7.11 Shunt capacitors
8 CALCULATION OF SHORT-CIRCUIT CURRENTS IN THE FAULT
8.1 Far-from-generator short-circuits
8.2 Near-to-generator short-circuits
8.3 Meshed and radial systems
8.4 Initial symmetrical r.m.s value (Ik")
8.4.1 General
8.4.2 Three-phase short-circuit
8.4.2.1 General
8.4.2.2 Single-source short-circuits
8.4.2.3 Short-circuits fed from unmeshed sources
8.4.2.4 Short-circuits in meshed networks
8.4.3 Line-to-line short-circuits
8.4.4 Line-to-line-to-earth short-circuits
8.4.5 Line-to-earth short-circuit
8.5 Peak short-circuit current (ip)
8.5.1 General
8.5.2 Three-phase short-circuit
8.5.2.1 Short-circuits fed from unmeshed sources
8.5.2.2 Short-circuits in meshed networks
8.5.3 Line-to-line short-circuits
8.5.4 Line-to-line-to-earth short-circuits
8.5.5 Line-to-earth short-circuits
8.6 Breaking current
8.6.1 General
8.6.2 Symmetrical breaking current
8.6.2.1 Far-from-generator short-circuits
8.6.2.2 Near-to-generator short-circuits
8.6.2.3 Breaking currents for balanced faults in radial networks
8.6.2.4 Breaking currents for faults in meshed networks
8.6.3 Aperiodic component of the breaking current
8.7 Steady-state short-circuit current
8.7.1 General
8.7.2 Contribution to three phase short-circuits from radially connected generators
8.7.2.1 General
8.7.2.2 Maximum steady-state short-circuit current (Ik, max.)
8.7.2.3 Minimum steady-state short-circuit current
8.7.2.4 Radial connection via a transformer
8.7.3 Unbalanced short-circuits
8.8 JOULE INTEGRAL I2t OF A SHORT-CIRCUIT CURRENT
9 INFLUENCE OF MOTORS
9.1 Synchronous motors and synchronous compensators
9.2 Asynchronous motors
9.2.1 Motor contribution
9.2.2 Low voltage motors
9.2.3 Breaking currents
9.2.4 Balanced three-phase short-circuit on asynchronous motors
9.2.5 Unbalanced short-circuits on asynchronous motors
9.2.6 Short-circuit beyond an impedance
9.3 Static converter fed drives
10 DISTRIBUTION OF SHORT-CIRCUIT CURRENTS IN NETWORKS FEEDING THE FAULT
APPENDIX A
APPENDIX B
APPENDIX C
C1 INTRODUCTION
C2 STAR-STAR
C3 STAR-DELTA
C4 STAR-ZIG-ZAG
C5 STAR WINDING AUTO TRANSFORMER WITH DELTA TERTIARY
C6 STAR-STAR TRANSFORMER WITH DELTA TERTIARY
APPENDIX D
D1 INTRODUCTION
D2 EXAMPLE 1
D3 EXAMPLE 2
D4 EXAMPLE 3
D5 EXAMPLE 4
D6 EXAMPLE 5
D7 EXAMPLE 6
D8 EXAMPLE 7
D9 EXAMPLE 8
D10 EXAMPLE 9
D11 EXAMPLE 10
D12 EXAMPLE 11
D13 EXAMPLE 12
D14 EXAMPLE 13
D15 EXAMPLE 14
D16 EXAMPLE 15
APPENDIX E
E1 INTRODUCTION
E2 CONVERSION OF DATA TO COMMON PER UNIT BASE
E3 CALCULATION OF THREE PHASE SHORT CIRCUIT CURRENTS AT FAULT LOCATION (FA)
E3.1 General
E3.2 Initial symmetrical short-circuit current
E3.3 Peak short-circuit current
E3.4 Symmetrical breaking current
APPENDIX F
Cited references in this standard
[Superseded]
Electrical installations — Selection of cables, Part 1: Cables for alternating voltages up to and including 0.6/1 kV
Content history
[Current]
[Superseded]
IEC 60865
AS 3851-1991 Rec:2015
IEC 909-1988
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