POWER QUALITY VAR Compensat ion in Power Systems

R. Sastry Vedam Mulukutla S. Sarma

Lßp) CRC Press VV1^ J Taylor & Francis Group

Boca Raton London New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

Contents

Chapter 1 Power Quality 1 1.1 Introduction 1 1.2 Importance of Power Quality 1 1.3 Common Disturbances in Power Systems 2 1.4 Short-Duration Voltage Variation 2 1.5 Long-Duration Voltage Variations 4 1.6 Transients 4

1.6.1 Impulsive Transients 4 1.6.2 Oscillatory Transients 5 1.6.3 Voltage Imbalance 5

1.7 Harmonics 6 1.8 Interharmonics 6 1.9 DC Offset 7 1.10 Notching 7 1.11 Noise 7 1.12 Voltage Fluctuations 8 1.13 Power Frequency Variations 8 1.14 Solutions to Power Quality Problems 8 1.15 Ambiguous Terms 10 1.16 CBEMA and ITI Curves 10 1.17 Features of Voltages in Power Systems 11 1.18 Grounding 11

1.18.1 Ground Electrodes 12 1.18.1.1 Ground Rods, Ground Rings, Plates 13 1.18.1.2 Signal Reference Ground (SRG) 14

1.18.2 Single-Point and Multipoint Grounding 14 1.18.3 Ground Loops 17 1.18.4 Isolated Ground 17 1.18.5 Electrochemical Reactions Due to Ground Grids 17

1.19 Reactive Power in Power Systems with Harmonic Distortion 18 1.19.1 Single-Phase Systems 18

1.20 Reliability 20 1.21 Power Quality Data Collection 20 1.22 Summary 21 Appendix 22 References 24

Chapter 2 Static Var Compensators 27 2.1 Introduction 27

2.1.1 Increase in Transient Stability Margin 27 2.1.2 Damping of Power Oscillations 27 2.1.3 Voltage Support 29

2.2 Static Var Compensator Systems Versus Synchronous Condensers, Capacitors, and Reactors 30

2.3 Shunt and Series Compensation 31 2.4 Fundamentals of Load Compensation 31 2.5 Reactive Power Relationships Between Wye- and Delta-Connected

Systems 34 2.6 Static Var Compensators for Transmission Systems 39

2.6.1 SVC Using a TCR and an FC : 40 2.6.2 SVC Using a TCR and TSC 42 2.6.3 STATCOM (SVC Using Self-Commutated Inverters) 42 2.6.4 SVC Using a Saturated Reactor (SR) 43 2.6.5 Comparison of Static Var Systems 46 2.6.6 Specification of SVCs 46

2.7 A Case Study (Australia): Central Queensland Railway Project 47 2.7.1 Limits for Voltage Unbalance 48 2.7.2 Three-Phase Power Flow Studies 49

2.8 Chester-Maine SVC Project 51 2.9 Conclusions 51 References 52

Chapter 3 Control of Static Var Compensators 55 3.1 Introduction 55 3.2 Control Systems for SVCs in Transmission System Applications 55

3.2.1 Voltage Regulation 55 3.2.2 Gain Supervision 56 3.2.3 Reactive Power Control and Coordination 57 3.2.4 Control Signals for System Transient Stability, Power

Oscillation Damping, and Subsynchronous Resonance Damping Enhancement 58

3.3 Control Systems for SVCs in Traction Applications 59 3.3.1 Load Compensation 59 3.3.2 Voltage Regulation and Balancing 61 3.3.3 Measurement of Sequence Components 62

3.4 Phase-Locked Oscillator Control System 65 3.5 Implementation Details of a Programmable High-Speed Controller 65

3.5.1 Priority Logic 66 3.5.2 Detection of Faults 66

3.5.3 Program Sequence 67 3.5.4 Special Features of the Programmable High-Speed Controller 67

3.6 Conclusions 67 References 68

Chapter 4 Harmonics 71 4.1 Converter Harmonics 72

4.1.1 Effect of Transformer Connections 74 4.1.2 Harmonics When There Is Overlap in the Commutation

Process 75 4.1.3 Direct-Voltage Harmonics 76 4.1.4 Imperfect System Conditions 77

4.2 Single-Phase Power Supplies 79 4.3 DC Drives 81 4.4 AC Drives 81 4.5 Pulse-Width Modulation (PWM) 82 4.6 Telecontrol Signals 84 4.7 Cycloconverters 84 4.8 Transformers 84

4.8.1 Harmonics in No-Load Exciting Current 84 4.8.2 Harmonics due to Inrush Current 85 4.8.3 DC Magnetization 85

4.9 Harmonics in Rotating Machines 86 4.10 Harmonics in Arc Furnace Loads 87 4.11 Harmonics in a Thyristor-Controlled Reactor 87 4.12 TheK-Factor 88 4.13 Conclusions 90 References 90

Chapter 5 Utility Harmonic Regulations and Standards 93 5.1 Introduction 93 5.2 Undesirable Effects of the Harmonics 93 5.3 Specification of the Harmonic Limits 96 5.4 Philosophical Differences between IEEE 519-1992

and IEC 61000-Series Standards 97 5.5 IEEE 519-1992 97 5.6 IEC 61000-Series Standards 100

5.6.1 Assessment Procedure (Harmonic Limits) 101 5.6.2 Summation Laws for Combining Harmonics 104

5.7 General Comments on the Standards 105 5.7.1 Allocation of Harmonic Voltage or Current or Both Limits

to the Customers 105

5.7.2 Empirical Nature of the Standards 106 5.7.3 Legal Responsibility for Damages due to Harmonic Problems 107

5.8 Application of the Standards 107 5.8.1 Application of Standards—B.C. Hydro's Approach 108

5.9 Examples of the Harmonic Studies 111 5.10 Conclusions Ill References 112 Appendix—IEC 61000-Series Standards 113

Chapter 6 Harmonic Filters 117 6.1 Introduction 117 6.2 Undesirable Effects of Harmonics 117 6.3 Harmonic Sources 117 6.4 Types of Filters 118

6.4.1 Types of Damped Filters 118 6.5 AC Network Impedance 119

6.5.1 Overhead Lines 119 6.5.1.1 Line Constants 120

6.5.2 Underground Cables 121 6.5.3 Transformers 121 6.5.4 Rotating Machines 122 6.5.5 Passive Loads 123

6.5.5.1 Electronic Loads 123 6.5.6 Norton Equivalents of Residential Loads 123

6.6 Design of Single-Tuned Filters 124 6.7 Design of Double-Tuned Filters 127 6.8 Filter Performance Evaluation 127 6.9 Design of Damped Filters 129 6.10 Filter Component Ratings 130

6.10.1 Filter Capacitors 130 6.10.2 Tuning Reactors 131

6.11 Outline of Filter Design in Two Queensland (Australia) Projects 132 6.11.1 Transmission SVC Project 132 6.11.2 Queensland Railway (QR) Project 133

6.12 Conclusions 135 References 135

Chapter 7 Computational Tools and Programs for the Design and Analysis of Static Var Compensators and Filters 137 7.1 Introduction 137 7.2 Computational Tools 137 7.3 Digital Computers 138 7.4 Analog Computers 139

7.5 Special Problems in the Simulation of Power Electronic Circuits 139 7.5.1 Constant Topology 139 7.5.2 Varying Topology 140

7.6 Transient Electrical Network Analyzers 141 7.7 Special-Purpose Simulators 141 7.8 Computer Programs 141

7.8.1 PSS TM E Version 30 142 7.8.2 EMTP 143

7.8.2.1 Inductance 143 7.8.2.2 Capacitance 144 7.8.2.3 Lossless Line 144 7.8.2.4 Nodal Equations 146 7.8.2.5 Frequency Scan Facility 146

7.8.3 ATP 149 7.8.4 PSCAD/EMTDC 149 7.8.5 SuperHarm 149

7.8.5.1 SuperHarm Models 150 7.8.5.2 SuperHarm Solution Procedure 150 7.8.5.3 Support Options 151 7.8.5.4 Pricing and Availability 151

7.8.6 Three-Phase Power Flow Programs 151 7.8.6.1 Powerlink Program 151 7.8.6.2 HARMFLO Program 152

7.9 DADiSP 152 7.10 Conclusions 153 References 154

Chapter 8 Monitoring Power Quality 155 8.1 Introduction 155 8.2 Site Surveys 156

8.2.1 Spectrum Analyzers 157 8.2.2 Special-Purpose Power System Harmonic Analyzers 157 8.2.3 Transient-Disturbance Analyzers 157 8.2.4 Combination Disturbance and Harmonic Analyzers 158 8.2.5 Flicker Meters 158

8.3 Transducers 158 8.3.1 Measurement of the Frequency Response of Instrument

Transformers 159 8.3.2 Description of the Instrument Transformers' Tests 162 8.3.3 Summary of the Conclusions from the Tests 164

8.3.3.1 Voltage Transformers 166 8.4 IEC-Recommended Measurement Techniques for Harmonics 167

8.4.1 Harmonics 167 8.4.1.1 RMS Value of a Harmonic Group: Ggn 169 8.4.1.2 RMS Value of a Harmonic Subgroup: Gsgn 169

8.4.2 Total Harmonie Distortion (THD) 169 8.4.2.1 Group Total Harmonie Distortion (THDG) 170 8.4.2.2 Subgroup Total Harmonie Distortion (THDS) 170 8.4.2.3 Partial Weighted Harmonie Distortion (PWHD) 170

8.4.3 Interharmonics 170 8.4.3.1 RMS Value of an Interharmonic Component 170 8.4.3.2 RMS Value of an Interharmonic Group (C/fc„) 171 8.4.3.3 RMS Value of an Interharmonic-Centered Subgroup

(Cisg,n) 171 8.4.4 Relative and Absolute Harmonic Phase Angle Measurement 172

8.5 Necessity for the Measurement of Harmonic Voltages and Currents 173 8.6 Harmonic Monitoring System 173 8.7 Continuous Harmonic Analysis in Real Time (CHART) 173 8.8 Presentation of Harmonic Measurements 175 8.9 Examples of Projects Needing Harmonic Monitoring in the Powerlink

Queensland System, Australia 177 8.9.1 Aluminum Smelter Project 177 8.9.2 Central Queensland Railway Electrification Project 178

8.10 Flicker 179 8.11 IEC Flicker Meter 180

8.11.1 Short-Term Flicker Evaluation 183 8.11.2 Flicker Standards 184

8.12 Conclusions 185 References 185

Chapter 9 Reactors 189 9.1 Introduction 189 9.2 Losses in the Power System 189 9.3 Switching Surges 190 9.4 Shunt Reactor Installations in EHV Lines 191 9.5 Determination of Shunt Reactor Rating 191 9.6 Choice of Voltage Level for Shunt Reactor Connection 192

9.6.1 Effective Compensation 192 9.6.2 Influence on Transformers and Generators 192 9.6.3 Switchgear Requirements 193 9.6.4 Influence on Operation Reliability of the System 193 9.6.5 Influence on Insulation and Overvoltage Conditions 193

9.7 Single-Pole Autoreclosing of Transmission Lines 193 9.7.1 Arc Extinction with Single-Pole Switching 194 9.7.2 Laboratory Tests to Determine the Secondary Arc-Extinction

Time 195 9.7.3 Choice of Neutral Reactor 196 9.7.4 Secondary Arc Current and Recovery Voltage 197 9.7.5 Single-Pole Autoreclosing of EHV Lines—Field Test Results 198

9.7.6 Effect of X[)IX[ Ratio and Xn on the Secondary Arc Current and Neutral Voltage 201

9.7.7 Effect of Transposition Phasing of Double-Circuit Lines 206 9.7.8 Selective-Pole Switching of Long Double-Circuit EHV Line 207

9.8 Types of Reactors Based on Their Function 208 9.9 Construction of Reactors 208

9.9.1 Types of Reactors Based on Their Construction 209 9.9.2 Testing of EHV Reactors 212

9.10 Conclusions 213 References 213

Chapter 10 Capacitors 215 10.1 Introduction 215 10.2 Capacitor Banks 216

10.2.1 Fuses 217 10.3 Capacitor Bank Connections 217

10.3.1 Ungrounded Wye-Connected Banks 217 10.3.2 Grounded Wye-Connected Banks 218 10.3.3 Delta-Connected Banks 218

10.4 Protection of Capacitor Banks 218 10.4.1 Protection of Grounded Wye-Connected Capacitor Banks 218

10.5 Capacitor Bank Switching 226 10.5.1 Evaluation of Different Methods for Mitigating Remote

Overvoltages due to Shunt Capacitor Energization 226 10.5.2 Series Reactors for Capacitors 228 10.5.3 Location of Series Reactors for Capacitors 229 10.5.4 Transient-Free Switching of Capacitors 229

10.6 Series Capacitors 230 10.6.1 Protection of Series Capacitors 231 10.6.2 NGH Scheme for Damping Subsynchronous Resonance 234 10.6.3 Limitations of Series Capacitor Applications 235

10.6.3.1 Ferroresonance 235 10.6.3.2 Hunting of Synchronous Motors 236 10.6.3.3 Subsynchronous Resonance 236 10.6.3.4 Self-Excitation of Induction and Synchronous

Machines 237 10.7 Metal Oxide Varistors (MOVs) 237

10.7.1 Modeling of MOVs in Computer Simulations 238 10.8 Conclusions 239 References 240

Chapter 11 Fast Fourier Transforms 243 11.1 Fourier Series 243 11.2 Symmetrical Properties of Waveforms 245

11.3 Sine Function 246 11.4 Discrete Fourier Transform (DFT) 247 11.5 Fast Fourier Transform (FFT) 249

11.5.1 Decimation in Time (DIT) 249 11.5.2 Decimation in Frequency (D1F) 250 11.5.3 Some Computational Details of FFT Algorithms 252

11.6 Cooley-Tukey Algorithm 254 11.7 FFT of Two Real Functions Simultaneously 257 11.8 Mixed-Radix FFT 258 11.9 Split-Radix FFT 259 11.10 FFT Pruning 260 11.11 The Convolution Integral 260 11.12 Auto- and Cross-Correlation Functions 262 11.13 Pitfalls of the Discrete Fourier Transform 262

11.13.1 Aliasing 263 11.13.2 Spectral Leakage 263 11.13.3 The Picket-Fence Effect 264

11.14 Guidelines for Using FFT for Harmonic Analysis 266 References 267

Index 269