Protection of Modern Power Systems

Janaka Ekanayake, Ph.D. is a Senior Professor and the Chair of Electrical and Electronic Engineering of the University of Peradeniya, Sri Lanka. He is a Visiting Professor at the Institute of Energy at Cardiff University, UK, and an Honorary Professor of the University of Wollongong, Australia. He has published widely on intelligent electronic devices, renewable energy and power systems. Vladimir Terzija is a Professor of Newcastle University, UK. Prior to that he was a Full Professor and the Head of Laboratory of Modern Energy Systems at Skoltech, Moscow, Russian Federation. He has worked in the field of power system protection for over 25 years. He has published widely on power system protection and WAMPAC and is a member of the IEEE. Ajith Tennakoon is a Senior Power Systems Engineer for Vysus Group, Australia, involved in grid connection studies fowr renewable energy sources. He has extensive experience in Power System protection and has been heading the Transmission Network protection in Sri Lanka. Previously he was a senior protection engineer engaged in design and implementation of Generator protection systems in Sri Lanka. Athula Rajapakse is a Professor at the University of Manitoba, Canada. He leads the Intelligent Power Grid Laboratory at the University of Manitoba and has conducted a wide range of research related to power system protection, wide area protection and control, protection of future HVDC grids, and grid integration of renewable energy.

• Preface xiiiAbout the Authors xvList of Abbreviations xviiAbout the Companion Website xix1 Review of Principles of Protection 11.1 Introduction 11.2 Historical Development 11.3 Faults, Fault Currents, Voltages, and Protection 21.3.1 Types of Faults 21.3.2 Currents and Voltages under Fault Situations and Protection 21.4 Fault Current Contribution from Generators 51.5 Philosophy of Protection Relaying 51.5.1 Selectivity 51.5.2 Speed of Operation 51.5.3 Sensitivity 51.5.4 Reliability, Dependability, and Security 61.5.5 Primary and Backup Protection 61.5.6 Unit and Non-Unit Protection 61.6 Review Questions 61.7 Problems 62 Instrument Transformers 92.1 Introduction 92.2 Basic Principles of Operation 102.2.1 Shunt Mode 102.2.2 Series Mode 102.3 Current Transformers (CTS) 112.3.1 Steady-state Theory 112.3.2 Excitation Current 122.3.3 Excitation Characteristic 132.3.4 Terminal Marking and Polarity 132.3.5 CT Burden 142.3.6 CT Errors 142.3.7 Accuracy Classes 152.3.8 Accuracy Limit Factor 162.3.9 Rated Currents 162.4 Transient Response of CTs 172.4.1 Power System Fault Current 172.4.2 Flux Required to Transform the Primary Current 182.4.3 Transient Factor 192.4.4 Peak Transient Factor 202.4.5 Maximum Peak Transient Factor (Ktfp,max ) 212.4.6Transient Dimensioning Factor Ktd for Specific Time t'al 212.4.7 Rated Equivalent Limiting Secondary Voltage (Eal) 222.4.8 Primary Time Constant (TP) with Multiple Infeeds 232.4.9 Over-dimensioning Factor (Kh) Due Remanence 232.4.10 Duty Cycle 232.4.11 Auto-reclosing 232.4.12 Errors 242.4.13 CT Classes for Transient Performance 252.5 Selection of a CT 262.5.1 Rated Primary Current 262.5.2 Rated Secondary Current 262.5.3 Class, Burden, and ALF of the CTs 272.6 Voltage Transformers 322.6.1 Inductive Voltage Transformers 322.6.2 Inductive Voltage Transformer Errors 332.6.3 Inductive Voltage Transformer Classes 332.6.4 Inductive Voltage Transformer Selection 342.6.5 Terminal Marking 352.6.6 Inductive Voltage Transformer Transient Behaviour 352.6.7 Voltage Transformer Connections 352.7 Capacitor Voltage Transformer 362.7.1 Capacitive Voltage Transformer Errors 372.7.2 Capacitive Voltage Transformer Classes 372.7.3 Transient Behaviour 382.8 Non-Conventional Current and Voltage Transformers 392.8.1 Introduction 392.8.2 Non-Conventional CTs 402.8.3 Optical Voltage Transformers 452.9 Review Questions 452.10 Problems 463 Review of Principles of Protection 493.1 Introduction 493.2 Excess Current Protection 493.2.1 Discrimination by Current 503.2.2 Discrimination by Time 513.2.3 Discrimination by Time and Current 523.2.4 Inverse Characteristics 523.2.5 Grading of Relays 543.2.6 Co-ordination with Fuses 553.2.7 Plug Setting and Plug Setting Multiplier 563.2.8 Time Multiplier Setting 563.2.9 Discrimination When There Is a Delta-star Transformer 563.2.10 Earth Fault Protection 613.2.11 Directional Relaying 613.3 Differential Protection 623.3.1 Transformer Differential Protection 633.3.2 Protection Against Inter Turn Faults and Earth Faults 653.3.3 Feeder Differential Protection 703.4 Distance Protection 733.4.1 General Principles 733.4.2 Zones 743.4.3 Characteristic Presentation 753.4.4 Distance Relay Inputs for Three-Phase Faults and Phase-to-Phase Faults 753.4.5 Relationship Between Relay Voltage and ZS / ZL Ratio 763.4.6 Distance Measurement 773.4.7 Distance Relay Tele-protection Schemes 773.5 Overload Protection 793.5.1 Overhead Lines 803.5.2 Transformers 803.5.3 Generators 813.6 Load Shedding 813.7 Over-Flux Protection 843.8 Review Questions 843.9 Problems 854 Protection of Distributed Generation 914.1 Introduction 914.2 Fault Current Contribution from Different Generators 924.2.1 Synchronous Generators 924.2.2 Single-fed Induction Generators 934.2.3 Doubly-fed Induction Generators 944.2.4 Full Power Converter Generators 954.3 Protection of Distributed Generation 964.3.1 Protection of Faults within a DG 964.3.2 Protection Requirements for DGs Connected to a Distribution Network 974.3.3 Distribution System Earth Fault Protection 994.3.4 Mains Failure Protection 1004.4 Effect of DG on Distribution Network Protection 1014.4.1 Blinding of Protection 1014.4.2 False Tripping 1054.4.3 Issues with Recloser Operations 1084.4.4 Impact on Distance Protection 1104.5 Review Questions 1114.6 Problems 1115 Protection of Wind Farms 1155.1 Introduction 1155.2 Wind Turbine Configurations 1155.2.1 Fixed Speed Wind Turbines 1155.2.2 Doubly Fed Induction Generator Wind Turbines 1165.2.3 Fully Rated Wind Turbines 1165.3 Wind Turbine Fault Protection 1175.4 Protection of On-shore Wind Farms 1215.4.1 Protection Associated with Grid Interface 1215.4.2 Protection Associated with Collector Network 1245.4.3 Lightning and Surge Protection for Wind Farms 1285.5 Protection of Offshore Wind Farms 1295.5.1 Protection of LCC-HVDC 1315.5.2 Protection of VSC-HVDC 1315.6 Review Questions 1335.7 Problems 1346 Protection of PV Plants 1376.1 Introduction 1376.2 Components of a Solar PV Plant 1376.2.1 PV Cells, Modules, or Arrays 1376.2.2 Power Conversion and Conditioning Equipment 1416.2.3 Controller 1436.3 Protection of Rooftop Solar PV Systems 1436.4 Protection of Ground Mounted Solar PV Systems 1456.5 Review Questions 1516.6 Problems 1517 Signal Acquisition and Processing for Intelligent Electronic Devices 1537.1 Introduction 1537.2 Signal Parameters for an Intelligent Electronic Device 1537.2.1 Signals under Normal and Abnormal Conditions 1537.2.2 Spectral Content of CT/VT Measurements 1547.3 Nyquist Sampling Theorem and Aliasing 1557.4 A to D Conversion 1587.4.1 Sampling 1587.4.2 Quantisation and Encoding 1597.4.3 Issues with A to d 1607.4.4 A to D Conversion Techniques: Successive Approximation Method 1637.5 Discrete-Time Signal Analysis 1647.5.1 Discrete Fourier Transform 1657.6 Sine and Cosine Filter 1687.7 Review Questions 1727.8 Problems 1728 Numerical Relays 1758.1 Introduction 1758.2 Components of a Numerical Relay 1758.2.1 I/V Converter 1768.2.2 Anti-aliasing Filter 1768.2.3 Sample and Hold Circuit, Multiplexer, and A to D Converter (ADC) 1788.2.4 Microprocessor 1798.3 Numerical Overcurrent Relay 1808.4 Numerical Distance Relay 1808.5 Numerical Differential Protection 1868.6 Review Questions 1888.7 Problems 1889 Substation Automation and IEC 61850 1919.1 Introduction 1919.2 Substation Automation 1929.2.1 Input/Output Devices 1929.2.2 Relaying and Controlling Equipment 1929.2.3 Remote Terminal Units 1939.2.4 Station Computer 1939.2.5 Human-machine Interface 1939.2.6 Supervisory Control and Data Acquisition System 1949.3 Communication between Substation Equipment 1949.3.1 Physical Media for Communication 1949.3.2 Serial Communication 1969.4 Connection of Substation Equipment 1989.5 IEC 61850 2009.5.1 The IEC 61850 Data Model 2009.5.2 Time-critical Information Exchange 2069.5.3 Sampled Values 2099.5.4 SA Design 2109.6 Review Questions 2119.7 Problems 21210 Wide Area Monitoring, Protection, and Control Fundamentals 21510.1 System Needs for Wide Area Monitoring, Protection, and Control 21510.2 Synchronised Measurement Technology 21610.2.1 Definition of Synchrophasors 21710.2.2 Synchrophasor Measurement Errors 21810.2.3 Timing Sources 21910.2.4 Phasor Measurement Unit 22010.2.5 PMU Measurement Latency 22110.2.6 Phasor Data Concentrators 22210.2.7 Communication Infrastructure 22310.2.8 Architecture of Synchrophasor Measurement Systems 22410.2.9 Communication Networks for WAMPAC System 22510.3 Wide Area Monitoring, Protection, and Control Applications 22610.3.1 Post-disturbance Analysis and Model Validation 22810.3.2 Characterisation of Load Centres 22910.3.3 Monitoring of Parameters of Synchronous Generators 23210.3.4 PMU-based State Estimation 23310.3.5 PMU-based Monitoring of Inter-area Oscillations 23910.3.6 PMU-based Coordinated Power Oscillations Damping 24010.3.7 PMU-based Adaptive Underfrequency Load-shedding and Smart Frequency Control 24210.3.8 Adaptive PMU Based Fault Location Method 24510.3.9 Transmission Line Fault Location Based on Time Synchronised Samples 24810.4 Practical WAMPAC Examples and Installations 25210.4.1 Future Intelligent Transmission Network Substation (FITNESS) Project 25310.4.2 Visualisation of Real Time System Dynamics Using Enhanced Monitoring (VISOR) Project 25410.4.3 The Enhanced Frequency Control Capability (EFCC) Project 25810.5 Review Questions 260Index 265