Abstract:
This recommended practice provides short-circuit current information
including calculated short-circuit current duties for the application in industrial
plants and commercial buildings, at all power system voltages, of power system
equipment that senses, carries, or interrupts short-circuit currents. Equipment
coverage includes, but should not be limited to, protective device sensors such as
series trips and relays, passive equipment that may carry short-circuit current such
as bus, cable, reactors and transformers as well as interrupters such as circuit
breakers and fuses.
Keywords: available fault current, circuit breaker, circuit breaker applications,
fuse, power system voltage, reactors, short-circuit applications guides, shortcircuit duties
Contents
Chapter 1
Introduction
1.1 Scope
1.2 Definitions
1.3 Acronyms and abbreviations
1.4 Bibliography
1.5 Manufacturers’ data sources
Chapter 2
Description of a short-circuit current
2.1 Introduction
2.2 Available short-circuit
2.3 Symmetrical and asymmetrical currents
2.4 Short-circuit calculations
2.5 Total short-circuit current
2.6 Why short-circuit currents are asymmetrical
2.7 DC component of short-circuit currents
2.8 Significance of current asymmetry
2.9 The application of current asymmetry information
2.10 Maximum peak current
2.11 Types of faults
2.12 Arc resistance
2.13 Bibliography
Chapter 3
Calculating techniques
Introduction
3.2 Fundamental principles
3.3 Short-circuit calculation procedure
3.4 One-line diagram
3.5 Per-unit and ohmic manipulations
3.6 Network theorems and calculation techniques
3.7 Extending a three-phase short-circuit calculation procedures program
to calculate short-circuit currents for single-phase branches
3.8 Representing transformers with non-base voltages
3.9 Specific time period and variations on fault calculations
3.10 Determination of X/R ratios for ANSI fault calculations
3.11 Three winding transformers
3.12 Duplex reactor
3.13 Significant cable lengths
3.14 Equivalent circuits
3.15 Zero sequence line representation
3.16 Equipment data required for short-circuit calculations
3.17 Bibliography
Chapter 4
Calculating short-circuit currents for systems without ac delay
4.1 Introduction
4.2 Purpose
4.3 ANSI guidelines
4.4 Fault calculations
4.5 Sample calculations
4.6 Sample computer printout
4.7 Conclusions
4.8 Bibliography
Chapter 5
Calculating ac short-circuit currents for systems with contributions from
synchronous machines
5.1 Introduction
5.2 Purpose
5.3 ANSI Guidelines
5.4 Fault calculations
5.5 Nature of synchronous machine contributions
5.6 Synchronous machine reactances
5.7 One-line diagram data
5.8 Sample calculations
5.9 Sample computer printout
5.10 Sample computer printout for larger system calculations
5.11 Conclusions
5.12 Bibliography
Chapter 6
Calculating ac short-circuit currents for systems with contributions from
induction motors
6.1 Introduction
6.2 Purpose
6.3 ANSI guidelines
6.4 Fault calculations
6.5 Nature of induction motor contributions
6.6 Large induction motors with prolonged contributions
6.7 Data accuracy
6.8 Details of induction motor contribution calculations according to
ANSI standard application guides
6.9 Recommended practice based on ANSI-approved standards for representing
induction motors in multivoltage system studies
6.10 One-line diagram data
6.11 Sample calculations
6.12 Sample computer printout
6.13 Bibliography
Chapter 7
Capacitor contributions to short-circuit currents
7.1 Introduction
7.2 Capacitor discharge current
7.3 Transient simulations
7.4 Summary
7.5 Bibliography
Chapter 8
Static converter contributions to short-circuit currents
8.1 Introduction
8.2 Definitions of converter types
8.3 Converter circuits and their equivalent parameters
8.4 Short-circuit current contribution from the dc system to an
ac short circuit.
8.5 Analysis of converter dc faults
8.6 Short circuit between the converter dc terminals
8.7 Arc-back short circuits
8.8 Examples
8.9 Conclusions.
8.10 Bibliography
Chapter 9
Calculating ac short-circuit currents in accordance with ANSI-approved standards
9.1 Introduction
9.2 Basic assumptions and system modeling
9.3 ANSI recommended practice for ac decrement modeling
9.4 ANSI practice for dc decrement modeling
9.5 ANSI-conformable fault calculations
9.6 ANSI-approved standards and interrupting duties
9.7 One-line diagram layout and data
9.8 First cycle duty sample calculations
9.9 Interrupting duty sample calculations
9.10 Applying ANSI calculations to non-60 Hz systems
9.11 Normative references
9.12 Bibliography
Chapter 10
Application of short-circuit interrupting equipment
10.1 Introduction
10.2 Purpose
10.3 Application considerations
10.4 Equipment data
10.5 Fully rated systems
10.6 Low voltage series rated equipment
10.7 Low voltage circuit breaker short-circuit capabilities less than rating
10.8 Equipment checklist for short-circuit currents evaluation
10.9 Equipment phase duty calculations
10.10 Equipment ground fault duty calculations
10.11 Capacitor Switching
10.12 Normative references
Chapter 11
Unbalanced short-circuit currents.
11.1 Introduction
11.2 Purpose
11.3 ANSI guidelines
11.4 Procedure
11.5 Connection of sequence networks
11.6 Sample calculations
11.7 Conclusions
11.8 Bibliography
Chapter 12
Short-circuit calculations unser international standards
12.1 Introduction
12.2 System modeling and methodologies
12.3 Voltage factors
12.4 Short circuit currents per IEC 60909
12.5 Short circuits “far from generator”
12.6 Short circuits “near generator”
12.7 Influence of the motors
12.8 Fault calculations in complex systems
12.9 Comparing the ANSI-approved standards with IEC 909
12.10 Sample calculations.
12.11 Normative references
12.12 Bibliography
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