Национальный горный университет — соответствие Времени



UDC 621.311(075.8)
P 27

Confirmed by Ministry of Education and Science of Ukraine

Reviewers:

A. Shidlovsky, Academician of the National Academy of Sciences of Ukraine (The Institute of Electrodynamics of the National Academy of Sciences of Ukraine);

I. Zhezhelenko, Academician of the Academy of Sciences of Ukrainian Higher School, Ph.D, professor (Priazovye State Technical University);

The Department of Theoretical Electrical Engineering and Electric Power Supply of Vinnitsa State Technical University.

Authors: G. Pivnyak. V. Vinoslavskiy, A. Rybalka, L. Nesen, V. Prokopenko

Transients in Electric Power Supply Systems. Textbook for institutions of higher education. / G. Pivnyak, V. Vinoslavskiy, A. Rybalka, L. Nesen, V. Prokopenko; under the general editorship of G. Pivnyak, Academician of the National Academy of Sciences of Ukraine. Editorship of the English version and terminology by Professors O. Ivanov and S. Kostritskaya - 5th edition: Translation from Ukrainian. - Dnipropetrovsk: National Mining University. - 2009. - 406 pp.


ISBN 978-966-350-122-2

The electromagnetic and electromechanical processes in electric power supply systems are considered. Physical effects leading to transients and methods of their calculation are described. The material is assisted by control questions and topics for essay.

The textbook is meant for students of higher education institutions, for use in learning professional English in the field of electric power engineering. It can be used by undergraduate and post-graduate students, scientists and practical engineers for design, maintenance of electric power supply systems and enterprises, and also for training in the professional English language.

Розглянуті електромагнітні та електромеханічні процеси в системах електропостачання. Викладені фізичні явища, які обумовлюють перехідні процеси, методи їх аналізу і розрахунку. Матеріал супроводжується контрольними запитаннями для освоєння англійської мови у сфері професійної діяльності.

Для студентів вузів, які вчаться за спеціальностями електроенергетичних напрямів і вивчають англійську мову. Може бути використаний студентами, магістрами, аспірантами і інженерно-технічними працівниками для вирішення задач проектування, експлуатації систем електропостачання підприємств і виробництв, освоєння англійської мови.


© G. Pivnyak, V. Vinoslavskiy, A. Rybalka, L. Nesen, V .Prokopenko, 2009
© National Mining University, 2009


ISBN 978-966-350-122-2



CONTENTS

INTRODUCTION 9

PART 1 ELECTROMAGNETIC TRANSIENTS
 

CHAPTER
 1.

GENERAL INFORMATION ABOUT TRANSIENTS
14
 
1.1. Kinds, reasons and consequences of short circuits
15
  1.2. Purpose of electromagnetic transients calculation, design conditions 18
  1.3. Basic regularities of short circuit currents calculation 20
  1.4. Design circuit of electric power supply system and its components description 22
  1.5. Equivalent circuit and methods of its parameters calculation 25
  1.6. Transformations of equivalent circuits 32
  1.7. Application of approximate reduction in per unit 36
  Test questions 38
  Topics for essay 38

CHAPTER
 2.

TRANSIENTS AT THREE-PHASE SHORT CIRCUITS
39
 
2.1. Short circuit in radial network without transformer coupling
40
  2.2. Short circuit on generator's terminals 48
  2.3. Short circuit at remote points of electric supply network 52
  2.4. Initial value of periodic component of short circuit current 54
  2.5. Periodic component of short circuit current for any instant of time 57
  2.6. Short circuit current of emergency steady state 59
  Test questions 61
  Topics for essay 61

CHAPTER
 3.

EVALUATION OF TRANSIENTS UNDER THREE-PHASE SHORT CIRCUITS
62
 
3.1. Basic statements
63
  3.2. Use of short circuit periodical component diagrams in network with one source 64
  3.3. Use of short circuit current periodical component diagrams in a network with several sources 70
  3.4. Calculation of short circuit current periodical component for any time instant by rectified characteristics method 72
  3.5. Short circuit currents calculation on the principle of superposition 79
  3.6. Calculation of short circuit current components stipulated by load centers 81
  3.7. Calculation of short circuit currents in electrical installations with voltage up to 1 kV 91
  3.8. Computer-aided calculation of short circuit current 107
  Test questions 111
  Topics for essay 111

CHAPTER
 4.

KEY ITEMS CONCERNING ANALYSIS OF TRANSIENTS UNDER ASYMMETRY IN THREE-PHASE NETWORK
112
 
4.1. General information
113
  4.2. Generation of higher harmonics by synchronous generator 113
  4.3. Method of symmetric components 116
  4.4. Relationships between symmetrical components of current and voltage 119
  4.5. Resistances of negative and zero sequences of circuit elements 121
  4.6. Drawing up equivalent circuits for symmetrical components 138
  4.7. Resulting electromotive forces and impedances of equivalent circuits for separate sequences 141
  Test questions 142
  Topics for essay 143

CHAPTER
 5.

LATERAL ASYMMETRY.
144
 
5.1. Starting statements
145
  5.2. Single-phase short circuit 147
  5.3. Two-phase short circuit 149
  5.4. Two-phase short circuit to ground 152
  5.5. Account of contact resistance at the point of short circuit 154
  5.6. Equivalence rule for the current of positive sequence 156
  5.7. Integrated equivalent circuits 159
  5.8. Comparison of currents at different short circuits 162
  5.9. Symmetrical current and voltage components transformation 165
  5.10. Methods of asymmetrical short circuit calculation 172
  Test questions 177
  Topics for essay 177

CHAPTER
 6.

LONGITUDINAL ASYMMETRY AND COMPLEX FAULTS
178
 
6.1. General statements
179
  6.2. Open-phase fault in three-phase network 180
  6.3. Two-phases open fault 182
  6.4. Connection of unequal resistors in network phases 184
  6.5. Double ground connection 187
  6.6. Single-phase short circuit with simultaneous open-phase fault 193
  Test questions 196
  Topics for essay 196

CHAPTER
 7.

TRANSIENTS UNDER SPECIFIC CONDITIONS
197
 
7.1. Short circuits in the network of external electric power supply
198
  7.2. Short-circuit to ground in the network with insulated neutral 200
  7.3. Short circuits in the networks of increased frequency 205
  7.4. Transients stipulated by peculiarities of production process 205
  7.5. Processes taking place under capacitor banks commutation 208
  7.6. Short circuits in DC lines 210
  Test questions 215
  Topics for essay 215

CHAPTER
 8.

LEVELS OF CURRENTS AND POWER OF SHORT CIRCUIT
216
 
8.1. Quality of electromagnetic transients
217
  8.2. Ways of short circuit currents limiting 219
  8.3. Use of technical facilities for short circuit current level optimization 225
  8.4. Short circuit current level optimization 236
  8.5. Short circuit currents levels coordination 238
  Test questions 240
  Topics for essay 240

PART 2 ELECTROMECHANICAL TRANSIENTS
 

CHAPTER
 9.

ANALYSIS TASKS AND ELECTROMECHANICAL PROCESSES CHARACTERIZATION
241
 
9.1. Background of the problem
242
  9.2. Consequences of short-time failures in power supply 243
  9.3. Conditions of power supply system operation mode maintenance 244
  9.4. Mathematical models of power supply system components 245
  9.5. Modeling of industrial enterprise electric load for power supply system stability analysis 251
  Test questions 255
  Topics for essay 255

CHAPTER
 10.

METHODS OF STATIC STABILITY CALCULATION
256
 
10.1. Static stability criteria
257
  10.2. Application of practical static stability criteria 261
  10.3. Analysis of static stability by method of small oscillations 270
  10.4. Account of automatic excitation control in static stability calculations 278
  Test questions 287
  Topics for essay 287

CHAPTER
 11.

STABILITY OF ELECTRIC POWER SUPPLY SYSTEM OPERATION UNDER LARGE DISTURBANCES
288
 
11.1. Dynamic stability of operation
289
  11.2. Simplified methods of dynamic operation stability evaluation 292
  11.3. Estimation of dynamic operation stability of complex electric power system 296
  11.4. Estimation of dynamic stability of operation with account of generators excitation control 301
  11.5. Resulting operation stability 305
  11.6. Estimation of resulting operation stability 307
  11.7. Computation facilities application to study operation stability 311
  Test questions 312
  Topics for essay 312

CHAPTER
 12.

STABILITY OF LOAD NODES OPERATION UNDER SMALL DISTURBANCES
313
 
12.1. Starting positions
314
  12.2. Operation stability of induction and synchronous motors analysis 317
  12.3. Account of influence of electric line parameters on stability of load node operation 319
  12.4. Influence of reactive power compensation on stability of load node operation 324
  12.5. Use of load static characteristics for calculations of complex load node operation stability 329
  Test questions 333
  Topics for essay 333

CHAPTER
 13.

STABILITY OF LOAD NODE OPERATION AT LARGE DISTURBANCES
334
 
13.1. Typical causes of large disturbances occurrence in load nodes
335
  13.2. General set of equations for electromechanical transients in an induction motor 336
  13.3. Analysis of large disturbance having the form of three-phase fault on the terminals of an induction motor 338
  13.4. Analysis of large disturbance having the form of load surge on induction motor 340
  13.5. Starting induction motors 343
  13.6. Self-excitation of induction motors while starting with series capacitive compensation at the network 345
  13.7. Self-starting induction motors 347
  13.8. Equations of electromechanical transients in synchronous motor 350
  13.9. Analysis of large disturbance arising in the form of three-phase fault on terminals of a synchronous motor................................. 352
  13.10. Load surge on synchronous motor 353
  13.11. Starting synchronous motors 356
  13.12. Self-starting synchronous motors 358
  13.13. Electromechanical transients in complex load node 360
  Test questions 366
  Topics for essay 367

CHAPTER
 14.

ENSURING OPERATION STABILITY IN POWER SUPPLY SYSTEMS
368
 
14.1. General statements
369
  14.2. Ensuring power supply system operation stability in project stage 369
  14.3. Use of control means at electric power stations in operating conditions 373
  14.4. Use of protection devices and system automatic equipment 374
  Test questions 378
  Topics for essay 378

CHAPTER
 15.

MONITORING AND DIAGNOSTICS OF EMERGENCY OPERATION MODES
379
 
15.1. Initial statements
380
  15.2. Development of software for circuit diagrams and electric power supply system operation monitoring 382
  15.3. Program complex for distributive networks control 384
  15.4. Monitoring of transients 389
  15.5. Development of methods of short circuit points identification in high-voltage power transmission lines 390

REFERENCES
392

GLOSSARY
395



PREFACE
 

The need to improve electric supply systems is stipulated by development of industry, transport, civil engineering and the agroindustrial complex. These enterprises are the main consumers of electric power in complex infrastructure of industrial centers. They consume electric power with different frequencies, voltages and currents. They are also characterized by high density of electric loads. Their electric supply systems have multilevel stages of power distribution; large-scale load centers with different transformations of electromagnetic energy parameters, power consumers of various types; power sources of power system, local thermal power stations, synchronous compensators, sources of reactive power, in emergencies - motors went to generating mode; significant degree of branching; negative feedback of electric technological processes and powerful consumers on the system operation in emergencies.

Construction and maintenance of the electric power supply systems involves considerable material resources. That is why it is very important to improve their efficiency and reliability in different operating conditions, including malfunctions and post-emergency modes. This stipulates high requirements to these systems, to their operating modes and electric power quality. These requirements can be assessed on the basis of transient investigation.

Methods of investigation and evaluations of transients is the important field of research and development. Their aim is development of new level electric power supply systems, sustaining their modes stability with the required levels of economy, electric power quality, reliability, and maintenance safety. Use of simulation methods and computing facilities greatly contributes to solving tasks arising at analysis and evaluations of transients. They allow to choose the most appropriate circuit designs and electric characteristics of the system components, and also to forecast their economical and technical performances not only in normal, but also in transient modes.

The problems are analyzed with use of language structures, which will assist to students’ self-instruction, their comprehension of teaching material and mastering in modem research and evaluation principles in English.

The book consists of introduction and two parts. In the first part electromagnetic transients caused by shorts, longitudinal and lateral asymmetry are considered. Chapter 1 covers starting positions, basic assumptions and principles of equivalent representation for analysis of transients in electric power supply system. Equivalents of electric supply system elements and its mode parameters are the basis for construction of equivalent circuits (chapter 1), which are used for analytical (chapter 2) and practical (chapter 3) calculations of three-phase short circuits. Various types of lateral (chapter 5) and longitudinal (chapter 6) asymmetry, their combinations and complex faults are analyzed using the method of symmetrical components. Influence of technology and electric consumers operating modes on supply networks is illustrated in chapter 7. Measures of short circuit currents and power limitation are considered in chapter 8. Also conditions for their optimization are formulated.

The part two is devoted to electromechanical transients and to combined influence of the electromagnetic and electromechanical transients on power supply system operation stability. Investigation of the electromechanical transients unlike the electromagnetic processes is based on use of the power supply system characteristics and its components mathematical models (chapter 9). In chapters 10 and 11 techniques of analysis the power supply system important properties such as static and dynamic operation stability with reference to its part and to external power supply networks are described. Influence of large (chapter 12) and small (chapter 13) disturbances on load nodes of internal power supply networks are discussed. Possible measures providing the power supply system operation stability are resulted (chapter 14). In the chapter 15 methods of monitoring and diagnostics of the electric power system emergency operation modes are given.

There are control questions and topics for essays at the end of the chapters for better comprehension of the given material. They will help students' self-dependent activities in learning the discipline.

Authors will gratefully accept remarks and readers’ opinion, which will assist to further improvement of this text-book.

Authors

Acknowledgments

Authors wish to thank O. Balakhontsev, V. Gavrilyuk and L. Tokar, who have translated the book into English; Professors O. Ivanov and S. Kostritskaya for editing the English version of the textbook; assisting lecturers A. Siomin and S. Dybrin who have prepared the computer version of the edition.


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