Fault Location on Transmission and Distribution Lines: Principles and Applications

1 Introduction 1 1.1 Power System Faults 1 1.2 What Causes Shunt Faults? 4 1.3 Aim and Importance of Fault Location 18 1.4 Types of Fault-Locating Algorithms 21 1.5 How are Fault-Locating Algorithms Implemented? 25 1.6 Evaluation of Fault-Locating Algorithms 29 1.7 The Best Fault-Locating Algorithm 30 1.8 Summary 30 2 Symmetrical Components 33 2.1 Phasors 34 2.2 Theory of Symmetrical Components 35 2.3 Interconnecting Sequence Networks 37 2.4 Sequence Impedances of Three-Phase Lines 44 2.5 Exercise Problems 50 2.6 Summary 55 3 Fault Location on Transmission Lines 57 3.1 One-Ended Impedance-Based Fault Location Algorithms 57 3.1.1 Simple Reactance Method 60 3.1.2 Takagi Method 62 3.1.3 Modified Takagi Method 63 3.1.4 Current Distribution Factor Method 66 3.2 Two-Ended Impedance-Based Fault Location Algorithms 68 3.2.1 Synchronized Method 68 3.2.2 Unsynchronized Method 69 3.2.3 Unsynchronized Current-Only Method 70 3.2.4 Synchronized Line Current Differential Method 71 3.3 Three-Ended Impedance-Based Fault Location Algorithms 72 3.3.1 Synchronized Method 73 3.3.2 Unsynchronized Method 75 3.3.3 Unsynchronized Current-Only Method 76 3.3.4 Synchronized Line Current Differential Method 77 3.4 Traveling Wave Fault Location Algorithms 78 3.4.1 Single-Ended Traveling Wave Method 81 3.4.2 Double-Ended Traveling Wave Method 81 3.4.3 Error Sources 82 3.5 Exercise Problems 89 3.6 Summary 109 4 Error Sources in Impedance-Based Fault Location 111 4.1 Power System Model 111 4.2 Input Data Errors 113 4.2.1 DC Offset 113 4.2.2 CT Saturation 115 4.2.3 Aging CCVTs 118 4.2.4 Open-Delta VTs 118 4.2.5 Inaccurate Line Length 122 4.2.6 Untransposed Lines 122 4.2.7 Variation in Earth Resistivity 124 4.2.8 Non-Homogeneous Lines 127 4.2.9 Incorrect Fault Type Selection 128 4.3 Application Errors 128 4.3.1 Load 128 4.3.2 Non-Homogeneous System 130 4.3.3 Zero-Sequence Mutual Coupling 134 4.3.4 Series Compensation 140 4.3.5 Three-Terminal Lines 141 4.3.6 Radial Tap 142 4.3.7 Evolving Faults 143 4.4 Exercise Problems 144 4.5 Summary 150 5 Fault Location on Overhead Distribution Feeders 153 5.1 Impedance-Based Methods 160 5.1.1 Loop Reactance Method 161 5.1.2 Simple Reactance Method 167 5.1.3 Takagi Method 168 5.1.4 Modified Takagi Method 168 5.1.5 Girgis et al. Method 168 5.1.6 Santoso et al. Method 170 5.1.7 Novosel et al. Method 172 5.2 Challenges with Distribution Fault Location 173 5.2.1 Load 173 5.2.2 Non-Homogeneous Lines 174 5.2.3 Inaccurate Earth Resistivity 178 5.2.4 Multiple Laterals 178 5.2.5 Best Data for Fault Location: Feeder or Substation Relays 180 5.2.6 Distributed Generation 180 5.2.7 High Impedance Faults 184 5.2.8 CT Saturation 184 5.2.9 Grounding 185 5.2.10 Short Duration Faults 186 5.2.11 Missing Voltage 186 5.3 Exercise Problems 187 5.4 Summary 210 6 Distribution Fault Location With Current Only 211 6.1 Current Phasors Only Method 211 6.2 Current Magnitude Only Method 216 6.3 Short-circuit Fault Current Profile Method 224 6.4 Exercise Problems 226 6.5 Summary 246 7 System and Operational Benefits of Fault Location 247 7.1 Verify Relay Operation 248 7.2 Discover Erroneous Relay Settings 248 7.3 Detect Instrument Transformer Installation Errors 257 7.4 Validate Zero-Sequence Line Impedance 263 7.5 Calculate Fault Resistance 266 7.6 Prove Short-Circuit Model 267 7.7 Adapt Autoreclosing in Hybrid Lines 268 7.8 Detect the Occurrence of Multiple Faults 270 7.9 Identify Impending Failures and Take Corrective Action 274 7.10 Exercise Problems 274 7.11 Summary 284 Appendix A: Fault Location Suite in MATLAB 285 A.1 Understanding the Fault Location Script 285 References Index