The comprehensive guide for large turbo-generator operation and maintenance
The Handbook of Large Turbo-Generator Operation and Maintenance is an expanded 3rd edition of the authors’ second edition of the same book. This updated revision covers additional topics on generators and provides more depth on existing topics. It is the ultimate resource for operators and inspectors of large utility and industrial generating facilities who deal with multiple units of disparate size, origin, and vintage. The book is also an excellent learning tool for students, consulting and design engineers. It offers the complete scope of information regarding operation and maintenance of all types of turbine-driven generators found in the world.
Based on the authors' ver eighty combined years of generating station and design work experience, the information presented in the book is designed to inform the reader about actual machine operational problems and failure modes that occur in generating stations and other types of facilities. Readers will find very detailed coverage of:
- Design and construction of generators and auxiliary systems
- Generator operation and control, including interaction with the grid
- Monitoring, diagnostics, and protection of turbo-generators
- Inspection practices for the stator, rotor, and auxiliary systems
- Maintenance testing, including electrical and non-destructive examination
- Ideas on maintenance strategies and life cycle management
- Additional topics on uprating of generators and long term storage are also included
The Handbook of Large Turbo-Generator Operation and Maintenance comes packed with photos and graphs, commonly used inspection forms, and extensive references for each topic. It is an indispensable reference for anyone involved in the design, construction, operation, protection, maintenance, and troubleshooting of large generators in generating stations and industrial power facilities.
Table of Contents
Preface xxi
Acknowledgments xxvii
I THEORY, CONSTRUCTION, AND OPERATION
1 PRINCIPLES OF OPERATION OF SYNCHRONOUS MACHINES 3
1.1 Introduction To Basic Notions On Electric Power 4
1.1.1 Magnetism and Electromagnetism 4
1.1.2 Electricity 7
1.2 Electrical-Mechanical Equivalence 8
1.3 Alternating Current (ac) 8
1.4 Three-Phase Circuits 20
1.5 Basic Principles of Machine Operation 22
1.5.1 Faraday’s Law of Electromagnetic Induction 22
1.5.2 Ampere-Biot-Savart’s Law of Electromagnetic-Induced Forces 22
1.5.3 Lenz’s Law of Action and Reaction 23
1.5.4 Electromechanical Energy Conversion 24
1.6 The Synchronous Machine 26
1.6.1 Background 26
1.6.2 Principles of Construction 28
1.6.3 Rotor Windings 32
1.6.4 Stator Windings 34
1.7 Basic Operation of The Synchronous Machine 37
1.7.1 No-Load Operation 44
1.7.2 Motor Operation 46
1.7.3 Generator Operation 47
1.7.4 Equivalent Circuit 47
1.7.5 Machine Losses 50
Additional Reading 50
2 GENERATOR DESIGN AND CONSTRUCTION 53
2.1 Stator Core 55
2.1.1 General Construction Features 55
2.1.2 Insulated versus Noninsulated Cores 60
2.1.3 Cores Built with Consolidated “Donuts” 62
2.1.4 Robotic versus Hand Core Stacking 62
2.1.5 Core Stacking Pressure and Tightness 63
2.2 Stator Frame 64
2.2.1 General Construction Features 64
2.2.2 Caged Core Design 66
2.2.3 Grounding of Stator Frames 66
2.3 Flux and Armature Reaction 67
2.4 Electromagnetics 70
2.5 End-Region Effects and Flux Shielding 74
2.5.1 Stator Core-End Copper Flux Shields/Screens 75
2.5.2 Stator Core-End Flux Shunts 77
2.5.3 Combination Stator Core-End Flux Screens and Flux Shunts 78
2.5.4 Stator Core-End Packet Stepping 78
2.5.5 Stator Core-End Tooth Slitting 81
2.5.6 Keybar Shorting Straps 83
2.6 Stator Core and Frame Forces 84
2.7 Stator Windings 85
2.7.1 Stator Winding Configuration and Installation Overview 85
2.7.2 Overview of Stator Winding Design Considerations 89
2.7.3 Fundamental Concepts 93
2.7.4 Winding Structure 94
2.7.5 Winding Specific Layouts 95
2.7.6 Basic Formulae 96
2.7.7 Conductor Bar Construction 98
2.8 Stator Winding Wedges 111
2.9 End-Winding Support Systems 114
2.10 Stator Terminal Connections 117
2.11 Rotor Forging 118
2.12 Rotor Winding 124
2.13 Rotor Winding Slot Wedges 131
2.14 Amortisseur (Damper) Winding 133
2.15 Retaining Rings 133
2.16 Bore Copper and Terminal Connectors 143
2.17 Slip/collector Rings and Brush Gear 147
2.18 Rotor Couplings 149
2.19 Rotor Turning Gear 151
2.20 Bearings 152
2.21 Air and Hydrogen Cooling 152
2.21.1 Basic Cooling Arrangements 155
2.22 Rotor Fans 156
2.23 Hydrogen Containment 158
2.23.1 Journal-Type Hydrogen Seals 161
2.23.2 Thrust Collar-Type Hydrogen Seals 161
2.24 Hydrogen Coolers 162
2.25 Air Coolers 164
2.26 Water-Cooled Rotors 165
References 166
3 GENERATOR AUXILIARY SYSTEMS 169
3.1 Lube-Oil System 170
3.2 Hydrogen Cooling System 170
3.3 Seal-Oil System 173
3.4 Stator Cooling Water System 176
3.4.1 System Components 177
3.4.2 Stator Cooling Water Chemistry 180
3.4.3 Stator Cooling Water System Conditions 185
3.5 Exciter Systems 187
3.5.1 Types of Excitation Systems 187
3.5.2 Excitation System Performance Characteristics 192
3.5.3 Field Discharge Resistor 193
3.5.4 Automatic Voltage Regulator 196
3.5.5 Power System Stabilizer 198
4 OPERATION AND CONTROL 201
4.1 Basic Operating Parameters 202
4.1.1 Machine Rating 202
4.1.2 Apparent Power 203
4.1.3 Power Factor 205
4.1.4 Real Power 208
4.1.5 Reactive Power 209
4.1.6 Terminal Voltage 210
4.1.7 Stator Current 210
4.1.8 Field Voltage 212
4.1.9 Field Current 212
4.1.10 Speed 212
4.1.11 Hydrogen Pressure 212
4.1.12 Hydrogen Temperature 213
4.1.13 Short-Circuit Ratio 214
4.1.14 Volts Per Hertz and Overfluxing Events 214
4.2 Operating Modes 221
4.2.1 Shutdown 221
4.2.2 Turning Gear 222
4.2.3 Run-Up and Run-Down 224
4.2.4 Field Applied Off-Line (Open Circuit) 226
4.2.5 Synchronized and Loaded (Online) 226
4.2.6 Start-Up Operation 227
4.2.7 Online Operation 228
4.3 Machine Curves 229
4.3.1 Open-Circuit Saturation Characteristic 229
4.3.2 Short-Circuit Characteristic 229
4.3.3 Capability Curves 229
4.3.4 V-Curves 235
4.4 Special Operating Conditions 237
4.4.1 Unexcited Operation (“Loss-of-Field” Condition) 237
4.4.2 Negative-Sequence Currents 241
4.4.3 Off-Frequency Currents 242
4.4.4 Load Cycling and Repetitive Starts 243
4.4.5 Overloading 244
4.4.6 Extended Turning Gear Operation 245
4.4.7 Loss of Cooling 247
4.4.8 Overfluxing 248
4.4.9 Overspeed 256
4.4.10 Loss of Lubrication Oil 256
4.4.11 Out-of-Step Synchronization and “Near” Short Circuits 257
4.4.12 Ingression of Cooling Water and Lubricating Oil 259
4.4.13 Under- and Overfrequency Operation (U/F and O/F) 259
4.4.14 Brushes Bouncing Off the Sliprings due to Eccentricity and/or Vibration 261
4.5 Basic Operation Concepts 263
4.5.1 Steady-State Operation 263
4.5.2 Equivalent Circuit and Vector Diagram 264
4.5.3 Power Transfer Equations 264
4.5.4 Working with the Fundamental Circuit Equation 270
4.5.5 Parallel Operation of Generators 273
4.5.6 Stability 276
4.5.7 Sudden Short Circuits 290
4.6 System Considerations 291
4.6.1 Voltage and Frequency Variation 292
4.6.2 Negative-Sequence Current 292
4.6.3 Overcurrent 302
4.6.4 Current Transients 302
4.6.5 Overspeed 303
4.7 Grid-Induced Torsional Vibrations 303
4.7.1 Basic Principles of Shaft Torsional Vibration 303
4.7.2 Spring Model of a Turbo-Generator Shaft Train 305
4.7.3 Determination of Shaft Torque and Shaft Torsional Stress 308
4.7.4 Material Changes Due to Torsional Vibrations 308
4.7.5 Types of Grid-Induced Events 308
4.7.6 Monitoring of Torsional Vibration Events 315
4.7.7 Industry Experience and Alleviation Techniques 315
4.8 Excitation and Voltage Regulation 316
4.8.1 The Exciter 316
4.8.2 Excitation Control 317
4.9 Performance Curves 318
4.9.1 Loss Curves 318
4.9.2 Efficiency Curves 319
4.10 Sample of Generator Operating Instructions 319
References 330
5 MONITORING AND DIAGNOSTICS 331
5.1 Generator Monitoring Philosophies 332
5.2 Monitoring Versus Protection: Definition and Practice 333
5.3 Extent of Monitoring Versus Cost and Benefits 335
5.4 Simple Monitoring With Static High-Level Alarm Limits 335
5.5 Dynamic Monitoring With Load-Varying Alarm Limits 336
5.6 Artificial Intelligence Diagnostic Systems 342
5.7 Monitoring A Single Parameter Versus A Multifunction Instrument 345
5.8 Monitored Parameters 346
5.8.1 Generator Electrical Parameters 347
5.8.2 Stator Core and Frame 352
5.8.3 Stator Winding 364
5.8.4 Rotor 391
5.8.5 Excitation System 409
5.8.6 Hydrogen Cooling System 410
5.8.7 Lube-Oil System 415
5.8.8 Seal-Oil System 418
5.8.9 Stator Cooling Water System 421
References 427
6 GENERATOR PROTECTION 429
6.1 Basic Protection Philosophy 429
6.2 Generator Protective Functions 431
6.2.1 Protection Alarm Response 434
6.2.2 Protection Trip Response 435
6.3 Brief Description of Protective Functions 435
6.3.1 Synchronizer and Sync-Check Relays (Functions 15 and 25) 436
6.3.2 Short-Circuit Protection (Functions 21, 50, 51, 51V, and 87) 436
6.3.3 Volts/Hertz Protection (Function 24) 439
6.3.4 Over- and Undervoltage Protection (Functions 59 and 27) 443
6.3.5 Reverse Power Protection (Function 32) 443
6.3.6 Loss-of-Field Protection (Function 40) 445
6.3.7 Stator Unbalanced Current Protection (Function 46) 445
6.3.8 Stator and Rotor Thermal Protection (Function 49) 447
6.3.9 Voltage Balance Protection (Function 60) 448
6.3.10 Time Overcurrent Protection for Detection of Turn-to-Turn Faults (Function 61) 449
6.3.11 Breaker Failure Protection (Function 62B) 450
6.3.12 Rotor Ground-Fault Protection (Function 64F) 451
6.3.13 Stator Ground Fault Protection (Functions 27, 51, 59) 453
6.3.14 Stator Ground Fault Protection Utilizing Third Harmonic-Based Relays 454
6.3.15 Stator Ground Fault Protection by Low-Frequency Injection 455
6.3.16 Over-/Underfrequency Protection (Function 81) 455
6.3.17 Out-of-Step Operation (Loss of Synchronism, Function 78) 456
6.4 Specialized Protection Schemes 457
6.4.1 Protection against Accidental Energization 457
6.4.2 dc Field Ground Discrimination 459
6.4.3 Vibration Considerations 462
6.4.4 Operation of the Isolated-Phase Bus (IPB) at Reduced Cooling and Risks from H2 Leaks into the IPB 463
6.4.5 Calculation of the H2-Air Mixture in the IPB for a Given H2 Leak from the Generator into the IPB 465
6.4.6 Calculation of Stator and Rotor Amortisseur Motoring Currents 472
6.4.7 Numerical Example for Calculating Rotor Amortisseur Motoring Currents 474
6.4.8 Voltage Across Field Terminals During an Induction Motoring or Generation Event 474
6.5 Tripping and Alarming Methods 475
References 477
II INSPECTION, MAINTENANCE, AND TESTING
7 INSPECTION PRACTICES AND METHODOLOGY 481
7.1 Site Preparation 481
7.1.1 Foreign Material Exclusion 481
7.1.2 Foreign Material Exclusion: Procedures 487
7.2 Experience and Training 490
7.3 Safety Procedures 491
7.3.1 Mechanical Obstacle Avoidance and Electrical Clearances 491
7.3.2 Confined Space Entry 495
7.3.3 Plan for Emergency Extraction 496
7.4 Inspection Frequency 496
7.5 Generator Accessibility 497
7.6 Inspection Tools 499
7.7 Inspection Forms 505
References 520
8 STATOR INSPECTION 521
8.1 Stator Frame and Casing 522
8.1.1 External Components 522
8.1.2 Internal Components 536
8.1.3 Caged Stator Cores-Inspection and Removal 547
8.2 Stator Core 549
8.2.1 Stator Bore Contamination 549
8.2.2 Blocked Cooling Vent Ducts 552
8.2.3 Iron Oxide Deposits 553
8.2.4 Loose Core Iron/Fretting and Interlaminar Failures 555
8.2.5 Bent/Broken Laminations in the Bore 571
8.2.6 Space Block Support and Migration 572
8.2.7 Migration of Broken Core Plate and Space Block Thick Plates 573
8.2.8 Laminations Bulging into Air Vents 574
8.2.9 Greasing/Oxide Deposits on Core Bolts 575
8.2.10 Core-Compression Plates 577
8.2.11 Core-End Flux Screens and Flux Shunts 578
8.2.12 Frame-to-Core Compression (Belly) Bands 579
8.2.13 Back-of-Core Burning 580
8.2.14 Core-End Overheating 583
8.3 Stator Windings 586
8.3.1 Stator Bar/Coil Contamination (Cleanliness) 586
8.3.2 End-winding Blocking and Roving 587
8.3.3 Surge Rings 589
8.3.4 Surge-Ring Insulation Condition 593
8.3.5 End-winding Support Structures 593
8.3.6 Ancillary End-Winding Support Hardware 597
8.3.7 Asphalt Bleeding/Soft Spots 600
8.3.8 Tape Separation/Girth Cracking 602
8.3.9 Insulation Galling/Necking Beyond the Slot 604
8.3.10 Insulation Bulging into Air Ducts 605
8.3.11 Insulation Condition, Overheating, and Electrical Aging 605
8.3.12 Cracked or Broken Strands 608
8.3.13 Corona Activity 609
8.3.14 Stator Wedges 616
8.3.15 End-Wedge Migration Out of Slot 620
8.3.16 Side-Packing Fillers 620
8.3.17 Leaks in Water-Cooled Stator Windings 621
8.3.18 Magnetic Termites 624
8.3.19 Flow Restriction in Water-Cooled Stator Windings 626
8.3.20 Hoses, Gaskets, and O-Rings in Water-Cooled Stator Windings 629
8.4 Phase Connectors and Terminals 633
8.4.1 Circumferential Bus Insulation 633
8.4.2 Phase Droppers 635
8.4.3 High-Voltage Bushings 637
8.4.4 Standoff Insulators 637
8.4.5 Bushing Vents 639
8.4.6 Bushing-Well Insulators and Hydrogen Sealant Condition 639
8.4.7 Generator Current Transformers (CTs) 641
8.5 Hydrogen Coolers 644
References 646
Additional Reading 647
9 ROTOR INSPECTION 649
9.1 Rotor Cleanliness 650
9.2 Retaining Rings 652
9.2.1 Nonmagnetic 18-5 and 18-18 Retaining Rings 657
9.2.2 Removal of Retaining Rings 661
9.3 Fretting/movement At Interference-Fit Surfaces of Wedges and Rings 669
9.3.1 Tooth Cracking 669
9.4 Centering (Balance) Rings 679
9.5 Fan Rings Or Hubs 680
9.6 Fan Blades 682
9.7 Bearings and Journals 685
9.8 Balance Weights and Bolts 689
9.9 End Wedges, Slot Wedges, and Damper Windings 691
9.10 Other Wedges 696
9.11 Windings: General 696
9.11.1 Conductor Material 699
9.12 Windings: Slot Region 703
9.12.1 Slot Liner 703
9.12.2 Turn Insulation 705
9.12.3 Creepage Block and Top Channel 707
9.12.4 C-Channel Subslot 710
9.12.5 Radial-Tangential-Radial Cooling 711
9.13 End Windings and Main Leads 711
9.13.1 Retaining-Ring Liners 712
9.13.2 End Turns and Blocking 715
9.13.3 Shorted Turns 719
9.13.4 Top-Turn Cracking 721
9.13.5 dc Main Leads 724
9.13.6 Coil and Pole Connections 730
9.14 Collector Rings 735
9.15 Collector Ring Insulation 740
9.15.1 Collector Ring Surface Roughness 741
9.16 Bore Copper and Radial (Vertical) Terminal Stud Connectors 743
9.17 Brush-Spring Pressure and General Condition 749
9.18 Brush Rigging 752
9.19 Shaft Voltage Discharge (Grounding) Brushes 753
9.20 Rotor Winding Main Lead Hydrogen Sealing: Inner and Outer 755
9.21 Circumferential Pole Slots (Body Flex Slots) 760
9.22 Blocked Rotor Radial Vent Holes: Shifting of Winding And/or Insulation 762
9.23 Couplings and Coupling Bolts 764
9.24 Bearing Insulation 765
9.25 Hydrogen Seals 767
9.25.1 Journal Seals 768
9.25.2 Thrust-Collar Seals 769
9.25.3 Carbon Seals 771
9.26 Rotor Body Zone Rings 772
9.27 Rotor Removal 774
References 782
10 AUXILIARIES INSPECTION 785
10.1 Lube-Oil System 785
10.2 Hydrogen Cooling System 786
10.2.1 Hydrogen Desiccant/Dryer 787
10.3 Seal-Oil System 788
10.4 Stator Cooling Water System 790
10.5 Exciters 793
10.5.1 Rotating Systems Inspection 793
10.5.2 Static Systems Inspection 794
10.5.3 Brushless Systems Inspection 794
10.5.4 Specific Inspection Items 794
11 GENERATOR MAINTENANCE TESTING 801
11.1 Stator Core Mechanical Tests 801
11.1.1 Core Tightness 801
11.1.2 Core and Frame Vibration Testing 802
11.2 Stator Core Electrical Tests 804
11.2.1 EL CID Testing 804
11.2.2 Rated Flux Test with Infrared Scan 816
11.2.3 Core Loss Test 827
11.2.4 Through-Bolt Insulation Resistance 828
11.2.5 Insulation Resistance of Flux Screens 829
11.3 Stator Winding Mechanical Tests 829
11.3.1 Wedge Tightness 829
11.3.2 Stator End-Winding Vibration and Resonance (Bump) Testing 832
11.4 Water-Cooled Stator Winding Tests 836
11.4.1 Air Pressure Decay 836
11.4.2 Tracer Gases 837
11.4.3 Vacuum Decay 838
11.4.4 Pressure Drop 838
11.4.5 Flow Testing 838
11.4.6 Capacitance Mapping 838
11.5 Stator Winding Electrical Tests 839
11.5.1 Pretesting Requirements 840
11.5.2 Series Winding Resistance 840
11.5.3 Insulation Resistance (IR) 840
11.5.4 Polarization Index (PI) 841
11.5.5 Dielectric Absorption During dc Voltage Application 844
11.5.6 dc Leakage or Ramped Voltage 845
11.5.7 dc Hi-Pot 846
11.5.8 ac Hi-Pot 847
11.5.9 Partial Discharge (PD) Off-Line Testing 850
11.5.10 Capacitance Measurements 853
11.5.11 Dissipation/Power Factor Testing 854
11.5.12 Dissipation/Power Factor Tip-Up Test 855
11.6 Rotor Mechanical Testing 856
11.6.1 Rotor Vibration 856
11.6.2 Rotor Nondestructive Examination Inspection Techniques 857
11.6.3 Some Additional Rotor NDE Specifics 867
11.6.4 Air Pressure Test of Rotor Bore 871
11.7 Rotor Electrical Testing 873
11.7.1 Winding Resistance 873
11.7.2 Insulation Resistance (IR) 873
11.7.3 Polarization Index (PI) 873
11.7.4 dc Hi-Pot 874
11.7.5 ac Hi-Pot 875
11.7.6 Shorted Turns Detection: General 875
11.7.7 Shorted Turns Detection by Recurrent Surge Oscillation (RSO) 876
11.7.8 Shorted Turns Detection by Open-Circuit Test 879
11.7.9 Shorted Turns Detection by Winding Impedance 880
11.7.10 Shorted Turns Detection by Low-Voltage dc or Volt Drop 882
11.7.11 Shorted Turns Detection by Low-Voltage ac or “C-Core” Test 885
11.7.12 Shorted Turns Detection by Shorted Turns Detector (Flux Probe) 885
11.7.13 Field-Winding Ground Detection by the Split-Voltage Test 902
11.7.14 Field-Ground Detection by the Current-Through-Forging Test 904
11.7.15 Shaft Voltage and Grounding 904
11.8 Hydrogen Seals 906
11.8.1 NDE 906
11.8.2 Insulation Resistance 906
11.9 Bearings 906
11.9.1 NDE 906
11.9.2 Insulation Resistance 907
11.10 Thermal Sensitivity Testing and Analysis 907
11.10.1 Background 907
11.10.2 Typical Thermal Sensitivity Test 910
11.11 Heat-Run Testing 913
11.11.1 Test Procedure 913
11.11.2 Acceptance Parameters 915
11.12 Hydrogen Leak Detection 916
11.12.1 Pressure Drop 917
11.12.2 SF6 and CO2 Gas Detection 918
11.12.3 Helium Gas Detection 919
11.12.4 Snooping 920
11.12.5 Ultrasonic 920
References 920
12 MAINTENANCE 923
12.1 General Maintenance Philosophies 923
12.1.1 Breakdown Maintenance 925
12.1.2 Planned Maintenance 925
12.1.3 Predictive Maintenance 925
12.1.4 Condition-Based Maintenance (CBM) 927
12.2 Operational and Maintenance History 927
12.3 Maintenance Intervals/frequency 928
12.4 Type of Maintenance 929
12.4.1 Extent of Maintenance 929
12.4.2 Repair or Replacement 930
12.4.3 Rehabilitation/Upgrading/Uprating 931
12.4.4 Obsolescence 933
12.5 Work Site Location 936
12.5.1 Transportation 936
12.6 Workforce 938
12.7 Spare Parts 939
12.8 Uprating 941
12.8.1 Drivers for Uprating 941
12.8.2 Uprating Considerations 943
12.8.3 Component Evaluations 945
12.8.4 Reliability and Effect of Uprating on Generator Life 949
12.8.5 Required Inspection and Tests Prior to Uprating 951
12.8.6 Required Maintenance Prior to Uprating 952
12.8.7 Heat-Run Testing After Uprating 953
12.8.8 Maintenance Schedule After Uprating 955
12.9 Long-Term Storage and Mothballing 955
12.9.1 Reasons for Storage of Generator Equipment 956
12.9.2 General Requirements 956
12.9.3 Storage Requirements 958
12.9.4 Monitoring and Maintenance During Storage 963
12.9.5 Restoration from Storage 965
12.9.6 Long-Term Storage Maintenance Procedures and Testing 967
12.10 Life Cycle Management (LCM) 970
12.11 Single-Point Vulnerability (SPV) Analysis 972
References 973
13 NEW GRID CODES 975
13.1 New Grid Codes and Their Impact On Generators 975
13.2 Regulatory Requirements For Turbo-Generators 980
13.2.1 Verification of Real and Reactive Gross and Net Power Capacity 980
13.2.2 Verification of Models for Excitation Control Systems and Protection 982
References 984
Index 985
