This book provides readers with up-to-date coverage of fault location algorithms in transmission and distribution networks. The algorithms will help readers track down the exact location of a fault in the shortest possible time. Furthermore, voltage and current waveforms recorded by digital relays, digital fault recorders, and other intelligent electronic devices contain a wealth of information. Knowledge gained from analysing the fault data can help system operators understand what happened, why it happened and how it can be prevented from happening again. The book will help readers convert such raw data into useful information and improve power system performance and reliability.
Table of Contents
Preface ix
About the Companion Website xi
1 Introduction 1
1.1 Power System Faults 1
1.2 What Causes Shunt Faults? 4
1.3 Aim and Importance of Fault Location 16
1.4 Types of Fault-Locating Algorithms 19
1.5 How are Fault-Locating Algorithms Implemented? 21
1.6 Evaluation of Fault-Locating Algorithms 25
1.7 The Best Fault-Locating Algorithm 26
1.8 Summary 26
2 Symmetrical Components 27
2.1 Phasors 28
2.2 Theory of Symmetrical Components 29
2.3 Interconnecting Sequence Networks 31
2.4 Sequence Impedances of Three-Phase Lines 36
2.5 Exercise Problems 41
2.6 Summary 46
3 Fault Location on Transmission Lines 49
3.1 One-Ended Impedance-Based Fault Location Algorithms 49
3.1.1 Simple Reactance Method 52
3.1.2 Takagi Method 54
3.1.3 Modified Takagi Method 56
3.1.4 Current Distribution Factor Method 57
3.2 Two-Ended Impedance-Based Fault Location Algorithms 58
3.2.1 Synchronized Method 59
3.2.2 Unsynchronized Method 60
3.2.3 Unsynchronized Negative-Sequence Method 61
3.2.4 Synchronized Line Current Differential Method 62
3.3 Three-Ended Impedance-Based Fault Location Algorithms 62
3.3.1 Synchronized Method 63
3.3.2 Unsynchronized Method 65
3.3.3 Unsynchronized Negative-Sequence Method 66
3.3.4 Synchronized Line Current Differential Method 67
3.4 Traveling-Wave Fault Location Algorithms 68
3.4.1 Single-Ended TravelingWave Method 69
3.4.2 Double-Ended Traveling-Wave Method 71
3.4.3 Error Sources 71
3.5 Exercise Problems 77
3.6 Summary 93
4 Error Sources in Impedance-Based Fault Location 95
4.1 Power System Model 95
4.2 Input Data Errors 96
4.2.1 DC Offset 97
4.2.2 CT Saturation 99
4.2.3 Aging CCVTs 101
4.2.4 Open-Delta VTs 101
4.2.5 Inaccurate Line Length 104
4.2.6 Untransposed Lines 104
4.2.7 Variation in Earth Resistivity 106
4.2.8 Non-Homogeneous Lines 107
4.2.9 Incorrect Fault Type Selection 109
4.3 Application Errors 109
4.3.1 Load 109
4.3.2 Non-Homogeneous System 111
4.3.3 Zero-Sequence Mutual Coupling 111
4.3.4 Series Compensation 118
4.3.5 Three-Terminal Lines 119
4.3.6 Radial Tap 120
4.3.7 Evolving Faults 121
4.4 Exercise Problems 122
4.5 Summary 126
5 Fault Location on Overhead Distribution Feeders 129
5.1 Impedance-Based Methods 134
5.1.1 Loop Reactance Method 135
5.1.2 Simple Reactance Method 140
5.1.3 Takagi Method 140
5.1.4 Modified Takagi Method 141
5.1.5 Girgis et al. Method 141
5.1.6 Santoso et al. Method 143
5.1.7 Novosel et al. Method 144
5.2 Challenges with Distribution Fault Location 146
5.2.1 Load 146
5.2.2 Non-Homogeneous Lines 146
5.2.3 Inaccurate Earth Resistivity 149
5.2.4 Multiple Laterals 150
5.2.5 Best Data for Fault Location: Feeder or Substation Relays 151
5.2.6 Distributed Generation 152
5.2.7 High Impedance Faults 156
5.2.8 CT Saturation 156
5.2.9 Grounding 156
5.2.10 Short Duration Faults 157
5.2.11 Missing Voltage 157
5.3 Exercise Problems 158
5.4 Summary 177
6 Distribution Fault Location With Current Only 179
6.1 Current Phasors Only Method 179
6.2 Current Magnitude Only Method 184
6.3 Short-Circuit Fault Current Profile Method 191
6.4 Exercise Problems 193
6.5 Summary 208
7 System and Operational Benefits of Fault Location 209
7.1 Verify Relay Operation 210
7.2 Discover Erroneous Relay Settings 211
7.3 Detect Instrument Transformer Installation Errors 217
7.4 Validate Zero-Sequence Line Impedance 222
7.5 Calculate Fault Resistance 225
7.6 Prove Short-Circuit Model 226
7.7 Adapt Autoreclosing in Hybrid Lines 227
7.8 Detect the Occurrence of Multiple Faults 228
7.9 Identify Impending Failures and Take Corrective Action 232
7.10 Exercise Problems 232
7.11 Summary 239
A Fault Location Suite in MATLAB 241
A.1 Understanding the Fault Location Script 241
References 261
Index 269
