Disturbance Analysis for Power Systems

More than ninety case studies shed new light on power system phenomena and power system disturbances
Based on the author′s four decades of experience, this book enables readers to implement systems in order to monitor and perform comprehensive analyses of power system disturbances. Most importantly, readers will discover the latest strategies and techniques needed to detect and resolve problems that could lead to blackouts to ensure the smooth operation and reliability of any power system.
Logically organized, Disturbance Analysis for Power Systems begins with an introduction to the power system disturbance analysis function and its implementation. The book then guides readers through the causes and modes of clearing of phase and ground faults occurring within power systems as well as power system phenomena and their impact on relay system performance. The next series of chapters presents more than ninety actual case studies that demonstrate how protection systems have performed in detecting and isolating power system disturbances in:
Generators
Transformers
Overhead transmission lines
Cable transmission line feeders
Circuit breaker failures
Throughout these case studies, actual digital fault recording (DFR) records, oscillograms, and numerical relay fault records are presented and analyzed to demonstrate why power system disturbances happen and how the sequence of events are deduced. The final chapter of the book is dedicated to practice problems, encouraging readers to apply what they′ve learned to perform their own system disturbance analyses.
This book makes it possible for engineers, technicians, and power system operators to perform expert power system disturbance analyses using the latest tested and proven methods. Moreover, the book′s many cases studies and practice problems make it ideal for students studying power systems.

Spis treści :
Preface xvii
1 POWER SYSTEM DISTURBANCE ANALYSIS FUNCTION 1
1.1 Analysis Function of Power System Disturbances 2
1.2 Objective of DFR Disturbance Analysis 4
1.3 Determination of Power System Equipment Health Through System Disturbance Analysis 5
1.4 Description of DFR Equipment 6
1.5 Information Required for the Analysis of System Disturbances 7
1.6 Signals to be Monitored by a Fault Recorder 8
1.7 DFR Trigger Settings of Monitored Voltages and Currents 10
1.8 DFR and Numerical Relay Sampling Rate and Frequency Response 11
1.9 Oscillography Fault Records Generated by Numerical Relaying 11
1.10 Integration and Coordination of Data Collected from Intelligent Electronic Devices 12
1.11 DFR Software Analysis Packages 12
1.12 Verification of DFR Accuracy in Monitoring Substation Ground Currents 21
1.13 Using DFR Records to Validate Power System Short–Circuit Study Models 24
1.14 COMTRADE Standard 31
2 PHENOMENA RELATED TO SYSTEM FAULTS AND THE PROCESS OF CLEARING FAULTS FROM A POWER SYSTEM 33
2.1 Shunt Fault Types Occurring in a Power System 33
2.2 Classification of Shunt Faults 34
2.3 Types of Series Unbalance in a Power System 39
2.4 Causes of Disturbance in a Power System 39
2.5 Fault Incident Point 40
2.6 Symmetric and Asymmetric Fault Currents 41
2.7 Arc–Over or Flashover at the Voltage Peak 44
2.8 Evolving Faults 48
2.9 Simultaneous Faults 51
2.10 Solid or Bolted (RF¼0) Close–in Phase–to–Ground Faults 52
2.11 Sequential Clearing Leading to a Stub Fault that Shows a Solid (RF¼0) Remote Line–to–Ground Fault 53
2.12 Sequential Clearing Leading to a Stub Fault that Shows a Resistive Remote Line–to–Ground Fault 54
2.13 High–Resistance Tree Line–to–Ground Faults 56
2.14 High–Resistance Line–to–Ground Fault Confirming the Resistive Nature of the Fa ult Impedance When Fed from One Side Only (Stub) 58
2.15 Phase–to–Ground Faults on an Ungrounded System 59
2.16 Current in Unfaulted Phases During Line–to–Ground Faults 60
2.17 Line–to–Ground Fault on the Grounded–Wye (GY) Side of a Delta/GY Transformer 63
2.18 Line–to–Line Fault on the Grounded–Wye Side of a Delta/GY Transformer 65
2.19 Line–to–Line Fault on the Delta Side of a Delta/GY Transformer with No Source Connected to the Delta Winding 66
2.20 Subcycle Relay Operating Time During an EHV Double–Phase–to–Ground Fault 68
2.21 Self–Clearing of a C–g Fault Inside an Oil Circuit Breaker Tank 69
2.22 Self–Clearing of a B–g Fault Caused by a Line Insulator Flashover 70
2.23 Delayed Clearing of a Pilot Scheme Due to a Delayed Communication Signal 71
2.24 Sequential Clearing of a Line–to–Ground Fault 72
2.25 Step–Distance Clearing of an L–g Fault 74
2.26 Ground Fault Clearing in Steps by an Instantaneous Ground Element at One End and a Ground Time Overcurrent Element at the Other End 76
2.27 Ground Fault Clearing by Remote Backup Following the Failures of Both Primary and Local Backup (Breaker Failure) Protection Systems 78
2.28 Breaker Failure Clearing of a Line–to–Ground Fault 79
2.29 Determination of the Fault Incident Point and Classification of Faults Using a Comparison Method 81
3 POWER SYSTEM PHENOMENA AND THEIR IMPACT ON RELAY SYSTEM PERFORMANCE 85
3.1 Power System Oscillations Leading to Simultaneous Tripping of Both Ends of a Transmission Line and the Tripping of One End Only on an Adjacent Line 86
3.2 Generator Oscillations Triggered by a Combination of L–g Fault, Loss of Generation, and Undesired Tripping of Three 138–kV Lines 91
3.3 Stable Power Swing Generated During Successful Synchronization of a 200–MW Unit 95
3.4 Majo r System Disturbance Leading to Different Oscillations for Different Transmission Lines Emanating from the Same Substation 96
3.5 Appearance of 120–Hz Current at a Generator Rotor During a High–Side Phase–to–Ground Fault 98
3.6 Generator Negative–Sequence Current Flow During Unbalanced Faults 101
3.7 Inadvertent (Accidental) Energization of a 170–MW Hydro Generating Unit 102
3.8 Appearance of Third–Harmonic Voltage at Generator Neutral 104
3.9 Variations of Generator Neutral Third–Harmonic Voltage Magnitude During System Faults 106
3.10 Generator Active and Reactive Power Outputs During a GSU High–Side L–g Fault 107
3.11 Loss of Excitation of a 200–MW Unit 108
3.12 Generator Trapped (Decayed) Energy 110
3.13 Nonzero Current Crossing During Faults and Mis–Synchronization Events 112
3.14 Generator Neutral Zero–Sequence Voltage Coupling Through Step–Up Transformer Interwinding Capacitance During a High–Side Ground Fault 113
3.15 Energizing a Transformer with a Fault on the High Side within the Differential Zone 115
3.16 Transformer Inrush Currents 118
3.17 Inrush Currents During Energization of the Grounded–Wye Side of a YG/Delta Transformer 120
3.18 Inrush Currents During Energization of a Transformer Delta Side 121
3.19 Two–Phase Energization of an Autotransformer with a Delta Winding Tertiary During a Simultaneous L–g Fault and an Open Phase 124
3.20 Phase Shift of 30Across the Delta/Wye Transformer Banks 127
3.21 Zero–Sequence Current Contribution from a Remote Two–Winding Delta/YG Transformer 128
3.22 Conventional Power–Regulating Transformer Core Type Acting as a Zero–Sequence Source 129
3.23 Circuit Breaker Re–Strikes 130
3.24 Circuit Breaker Pole Disagreement During a Closing Operation 132
3.25 Circuit Breaker Opening Resistors 133
3.26 Secondary Current Backf eeding to Breaker Failure Fault Detectors 134
3.27 Magnetic Flux Cancellation 136
3.28 Current Transformer Saturation 138
3.29 Current Transformer Saturation During an Out–of–Step System Condition Initiated by Mis–Synchronization of a Generator Breaker 141
3.30 Capacitive Voltage Transformer Transient 143
3.31 Bushing Potential Device Transient During Deenergization of an EHV Line 144
3.32 Capacitor Bank Breaker Re–Strike Following Interruption of a Capacitor Normal Current 146
3.33 Capacitor Bank Closing Transient 147
3.34 Shunt Capacitor Bank Outrush into Close–in System Faults 149
3.35 SCADA Closing into a Three–Phase Fault 153
3.36 Automatic Reclosing into a Permanent Line–to–Ground Fault 154
3.37 Successful High–Speed Reclosing Following a Line–to–Ground Fault 155
3.38 Zero–Sequence Mutual Coupling–Induced Voltage 156
3.39 Mutual Coupling Phenomenon Causing False Tripping of a High–Impedance Bus Differential Relay During a Line Phase–to–Ground Fault 159
3.40 Appearance of Nonsinusoidal Neutral Current During the Clearing of Three–Phase Faults 162
3.41 Current Reversal on Parallel Lines During Faults 164
3.42 Ferranti Voltage Rise 166
3.43 Voltage Oscillation on EHV Lines Having Shunt Reactors at their Ends 168
3.44 Lightning Strike on an Adjacent Line Followed by a C–g Fault Caused by a Separate Lightning Strike on the Monitored Line 172
3.45 Spill Over of a 345–kV Surge Arrester Used to Protect a Cable Connection, Prior to its Failure 173
3.46 Scale Saturation of an A/D Converter Caused by a Calibration Setting Error 174
3.47 Appearance of Subsidence Current at the Instant of Fault Interruption 176
3.48 Energizing of a Medium Voltage Motor that has an Incorrect Formation of the Stator Winding Neutral 177
3.49 Phase Angle Change from Loading Condition to Fault Condition 179
4 CASE STUDIES RELATED TO GENERATOR SYSTEM DISTURBANCES 183
4.1 Generator Protection Basics 184
Case Studies 186
Case Study 4.1 Appearance of Double–Frequency (120–Hz) Current in a Hydrogenerator Rotor Due to Stator Negative–Sequence Current Flow During a 115–kV Phase–to–Ground Fault 186
Case Study 4.2 Inadvertent (Accidental) Energization of a 170–MW Hydro Unit 193
Case Study 4.3 Loss of Excitation for a 200–MW Generating Unit Caused by Human Error 204
Case Study 4.4 Loss–of–Excitation Trip in an 1100–MW Unit 212
Case Study 4.5 Mis–synchronization of a 50–MW Steam Unit for a Combined–Cycle Plant 214
Case Study 4.6 Mis–synchronization of a 200–MW Hydro Unit 222
Case Study 4.7 Undesired Tripping of a Numerical Differential Relay During Manual Synchronization of a Hydro Unit 231
Case Study 4.8 Tripping of a 500–MW Combined–Cycle Plant Triggered by a High–Side 138–kV Phase–to–Ground Fault 236
Case Study 4.9 Tripping of a 110–MW Combustion Turbine Unit in a Combined–Cycle Plant During a Power Swing 244
Case Study 4.10 Analysis of an 800–MW Generating Plant DFR Record for a Normally Cleared 345–kV Phase–to–Ground Fault 247
Case Study 4.11 Tripping of a 150–MW Combined–Cycle Plant Due to a Failed Lead of One Generator Terminal Surge Capacitor 250
Case Study 4.12 Generator Stator Ground Fault in an 800–MW Fossil Unit 260
Case Study 4.13 Three–Phase Fault at the Terminal of an 800–MW Generator Unit 265
Case Study 4.14 Three–Phase Fault at the Terminal of a 50–MW Generator Due to a Cable Connection Failure 271
Case Study 4.15 Generator Stator Phase–to–Phase–to–Ground Fault Caused by Failure of the Rotor Fan Blade 276
Case Study 4.16 Undesired Tripping of a Pump Storage Plant During a Close–in Phase–to–Ground 345–kV Line Fault 286
Case Study 4.17 Tripping of an 800–MW Plant and the Associated EHV Lines During a 345–kV Bus Fault 293
Case Study 4.18 Tripping of a 150–MW Combined–Cycle Plant During an External 138–kV Three–Phase Fault 296
Case Study 4.19 Tripping of a 150–MW Combined–Cycle Plant During a Disturbance in the 138–kV Transmission System 303
Case Study 4.20 Undesired Tripping of a 150–MW Combined–Cycle Plant Following Successful Clearing of a 138–kV Double–Phase–to–Ground Fault 308
Case Study 4.21 Undesired Tripping of an Induction Generator by a Differential Relay Having a Capacitor Bank Within the Protection Zone 311
Case Study 4.22 Undesired Tripping of a Steam Unit Upon Its First Synchronization to the System During the Commissioning Phase of a Combined–Cycle Plant 314
Case Study 4.23 Sequential Shutdown of a Steam–Driven Generating Unit as Part of a 500–MWCombined–Cycle Plant 318
Case Study 4.24 Wiring Errors Leading to Undesired Generator Numerical Differential Relay Operation During the Commissioning Phase of a New Unit 320
Case Study 4.25 Phasing a New Generator into the System Prior to Commissioning 324
Case Study 4.26 Third–Harmonic Undervoltage Element Setting Procedure for 100% Stator Ground Fault Protection 327
Case Study 4.27 Basis for Setting the Generator Relaying Elements to Provide System Backup Protection 330
5 CASE STUDIES RELATED TO TRANSFORMER SYSTEM DISTURBANCES 335
5.1 Transformer Basics 336
5.2 Transformer Differential Protection Basics 344
5.3 Case Studies 347
Case Study 5.1 Energization of a 5–MVA 13.8/4.16–kV Station Service Transformer with a 13.8–kV Phase–to–Phase Bus Fault Within the Transformer Differential Protection Zone 347
Case Study 5.2 Lack of Protection R edundancy for a Generator Step–up Transformer Leads to Interruption of a 230–kV Area 353
Case Study 5.3 Undesired Operation of a Numerical Transformer Differential Relay Due to a Relay Setting Error in the Winding Configuration 357
Case Study 5.4 Location of a 13.8–kV Switchgear Phase–to–Phase Fault Using Transformer Differential Numerical Relay Fault Records 363
Case Study 5.5 Operation of a Unit Step–Up Transformer with an Open Phase on the 13.8–kV Delta Winding 370
Case Study 5.6 Using a Transformer Phasing Diagram, Digital Fault Recorder Record, and Relay Targets to Confirm the Damaged Phase of a Unit Auxiliary Transformer Failure 375
Case Study 5.7 Failure of a 450–MVA 345/138/13.2–kV Autotransformer 381
Case Study 5.8 Failure of a 750–kVA 13.8/0.480–kV Station Service Transformer Due to a Possible Ferroresonance Condition 387
Case Study 5.9 Undesired Tripping of a Numerical Transformer Differential Relay During an External Line–to–Ground Fault 394
Case Study 5.10 Undesired Operation of Numerical Transformer Differential Relays During Energization of Two 75–MVA 138/13.8–kV GSU Transformers 407
Case Study 5.11 Undesired Operation of a Numerical Transformer Differential Relay During Energization of a 5–MVA 13.8/4.16–kV Station Service Transformer 411
Case Study 5.12 Phase–to–Phase Fault Evolving into a Three–Phase Fault at the High Side of a 5–MVA 13.8/4.16–kV Station Service Transformer 414
Case Study 5.13 Phase–to–Phase Fault Evolving into a Three–Phase Fault at the 13.8–kV Bus Connection of a 2–MVA 13.8/0.480–kV Station Service Enclosure 420
Case Study 5.14 Phase–to–Phase Fault in a 13.8–kV Switchgear Caused by Heavy Rain Evolving into a Three–Phase Fault 426
Case Study 5.15 Undesired Operation of a Numerical Transformer Differentia