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Disturbance Analysis for Power Systems

Disturbance Analysis for Power Systems

Mohamed A. Ibrahim

ISBN: 978-0-470-91681-0

Oct 2011

736 pages

In Stock



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.

Preface xvii


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


2.1 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 Fault 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


3.1 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 Major 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 Backfeeding 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


4.1 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


5.1 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 Redundancy 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 Differential Relay Due to a Missing CT Cable Connection as an Input to the Relay Wiring 430

Case Study 5.16 Phase-to-Ground Fault Caused by Flashover of a Transformer 115-kV Bushing Due to a Bird Droppings 434

Case Study 5.17 Using a Transformer Numerical Relay Oscillography Record to Analyze Phase-to-Ground Faults in a 4.16-kV Low-Resistance Grounding Supply 439

Case Study 5.18 Phase-to-Phase Fault Caused by a Squirrel in a 13.8-kVCable Bus Which Evolves into a Three-Phase Fault 447

Case Study 5.19 13.8-kV Transformer Lead Phase-to-Phase Fault Due to Animal Contact, Evolving into a 115-kV Transformer Bushing Fault 451

Case Study 5.20 Undesired Tripping of a Numerical Multifunction Transformer Relay by Assertion of a Digital Input Wired to the Buchholz Relay Trip Output 456


6.1 Line Protection Basics 463

6.2 Case Studies 466

Case Study 6.1 Using a DFR Record From One End Only to Determine Local and Remote-End Clearing Times for a Line-to-Ground Fault 466

Case Study 6.2 Analysis of Clearing Times for a Phase-to-Ground Fault from Both Ends of a 345-kV Transmission Line Using Oscillograms from One End Only 469

Case Study 6.3 Analysis of a Three-Phase Fault Caused by Lightning 471

Case Study 6.4 Analysis of a Double-Phase-to-Ground 765-kV Fault Caused by Lightning 473

Case Study 6.5 Assessment of Transmission Tower Footing Resistance by Analyzing a Three-Phase-to-Ground Fault Caused by Lightning 476

Case Study 6.6 115-kV Phase-to-Ground Fault Cleared First from a Solidly Grounded System, Then Connected and Cleared from an Ungrounded System 478

Case Study 6.7 345-kV Phase-to-Ground Fault (C-g) Caused by an Act of Vandalism 485

Case Study 6.8 345-kV Phase-to-Ground (A-g) Fault Due to an Accident Along the Line Right-of-Way 489

Case Study 6.9 False Tripping of a 138-kV Current Differential Relaying System During an External Phase-to-Ground Fault 495

Case Study 6.10 Undesired Operation of a 13.8-kV Feeder Ground Relay During a Three-Phase Fault Due to an Extra CT Circuit Ground 502

Case Study 6.11 Correction of a System Model Error from Analysis of a Failure of a Post Insulator Associated with a 115-kV Disconnect Switch 512

Case Study 6.12 Location of a 345-kV Line Fault Protected by Electromechanical Distance Relays Using Information from a DFR Record 519

Case Study 6.13 Location of an Outdoor 13.8-kV Switchgear Fault at a Cogeneration Facility Using a DFR Fault Record from a Remote Substation 524

Case Study 6.14 Breakage (Failure) of a 345-kV Subconductor Bundle During a High-Resistance Tree Fault, Due to the Heavily Loaded Line Sagging to a Tree 529

Case Study 6.15 115-kV Phase-to-Phase Fault Caused by Failure of a Circuit Switcher 536

Case Study 6.16 Undesired Tripping of a 115-kV Feeder Due to a Setting Application Error in the Time Overcurrent Element for a Numerical Line Protection Relay 539

Case Study 6.17 Mitigation of Mutual Coupling Effects on the Reach of Ground Distance Relays Protecting Highand Extrahigh-Voltage Transmission Lines 544


Case Studies 572

Case Study 7.1 Optimum Design of Relaying Protection Zones Leads to Quick Identification of a Faulted 345-kV Submarine Cable Section 572

Case Study 7.2 Undesired Operation of a 138-kV Cable Feeder Differential Relay During the Commissioning Phase of a 500-MW Plant 578

Case Study 7.3 Phase-to-Ground Fault Caused by Failure of a 345-kV Cable Connection Between the Generator and the Switchyard, Accompanied by Mechanical Failure of One of the Cable Pot Head Phases 588

Case Study 7.4 Troubleshooting a 345-kV Phase-to-Ground Fault Using Relay Targets Only 595

Case Study 7.5 Failure of a 345-kV Cable Connection Between a 300-MW Generator and a 345-kV Switchyard, Causing a Phase-to-Ground Fault 603

Case Study 7.6 138-kV Cable Pot Head Failure Analysis Using Numerical Current Differential Relay Oscillography and Event Records 607


8.1 Breaker Failure Protection Basics 616

Case Studies 626

Case Study 8.1 Tripping of a Combined-Cycle 150-MW Plant by Undesired Operation of a Solid-State Breaker Failure Relaying System 626

Case Study 8.2 115-kV Dual Breaker Failures Resulting in the Loss of a 1000-MW Plant and Associated Substations 634

Case Study 8.3 230-kV Substation Outage Due to Circuit Breaker Problems During the Clearing of a Close-in Phase-to-Ground Fault 640

Case Study 8.4 Failure of a 230-kV Circuit Breaker Leading to Isolation of a 1000-MW Plant and Associated Substations 646

Case Study 8.5 Generator CB Failure During Automatic Synchronization of the Circuit Breaker 654

Case Study 8.6 Circuit Breaker Re-strikes While Clearing Simultaneous Phase-to-Ground Faults on a 230-kV Double-Circuit Tower 660

Case Study 8.7 345-kV Capacitor Bank Breaker Fault Coupled with an Additional Failure of a Dual SF6 Pressure 345-kV Breaker During the Clearing of the Fault 664

Case Study 8.8 Oil Circuit Breaker Failure Following the Clearing of a Failed 230-kV Surge Arrester 671

Case Study 8.9 Detection of a Remote Circuit Breaker Problem from Analysis of a Local Oscillogram Monitoring Line Currents and Voltages 676

Case Study 8.10 Blackout of a 138-kV Load Area Due to a Primary Relay System Failure and the Lack of DC Control Power for the Secondary Relay System Circuit 678

Case Study 8.11 Installation of Two 345-kV Breakers in Series Within a Ring Substation Configuration to Mitigate the Loss of Critical Lines During Breaker Failure Events 682

Case Study 8.12 Design of Two 138-kV Circuit Breakers in Series to Fulfill the Need of Breaker Failure Protection 682


Index 715

""The author has published a unique and valuable reference book on disturbance analysis for power systems and is to be honored for his life-long dedication and significant contributions to the electric power community. His book enhances power system engineers to understand power system phenomena which impact protective relaying practices. Adequate and safe system operations is the result of understanding power system disturbances and protection system response during power system disturbances. I strongly recommend reading the author book, titled “Disturbance Analysis for Power Systems” published by Wiley on October, 2011, documenting his over 40 years of experience in the protection and control and system disturbance analysis areas.""— Simon R. Chano Hydro-Québec TransÉnergie