HANDBOOK OF LARGETURBO-GENERATOR

OPERATION AND MAINTENANCE

Geoff KlempnerIsidor Kerszenbaum

A JOHN WILEY & SONS, INC., PUBLICATION

IEEE Press

Mohamed E. El-Hawary, Series Editor

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InnodataFile Attachment9780470382707.jpg

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HANDBOOK OF LARGETURBO-GENERATOR

OPERATION AND MAINTENANCE

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Books in the IEEE Press Series on Power Engineering

Principles of Electric Machines with Power Electronic Applications, Second EditionM.E. El-Hawary

Pulse Width Modulation for Power Converters: Principles and PracticeD. Grahame Holmes and Thomas Lipo

Analysis of Electric Machinery and Drive Systems, Second EditionPaul C. Krause, Oleg Wasynczuk, and Scott D. Sudhoff

Risk Assessment for Power Systems: Models, Methods, and ApplicationsWenyuan Li

Optimization Principles: Practical Applications to the Operations of Markets of theElectric Power IndustryNarayan S. Rau

Electric Economics: Regulation and DeregulationGeoffrey Rothwell and Tomas Gomez

Electric Power Systems: Analysis and ControlFabio Saccomanno

Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing, and RepairGreg Stone, Edward A. Boulter, Ian Culbert, and Hussein Dhirani

Signal Processing of Power Quality DisturbancesMath H. J. Bollen and Irene Y. H. Gu

Instantaneous Power Theory and Applications to Power ConditioningHirofumi Akagi, Edson H. Watanabe and Mauricio Aredes

Maintaining Mission Critical Systems in a 24/7 EnvironmentPeter M. Curtis

Elements of Tidal-Electric EngineeringRobert H. Clark

Handbook of Large Turbo-Generator Operation and Maintenance, Second EditionGeoff Klempner and Isidor Kerszenbaum

ffirs.qxd 9/11/2008 9:31 AM Page ii

HANDBOOK OF LARGETURBO-GENERATOR

OPERATION AND MAINTENANCE

Geoff KlempnerIsidor Kerszenbaum

A JOHN WILEY & SONS, INC., PUBLICATION

IEEE Press

Mohamed E. El-Hawary, Series Editor

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Copyright 2008 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

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http://www.copyright.comhttp://www.wiley.com/go/permissionhttp://www.wiley.com

To our families:Susan Klempner,

Jackie, Livi, and Yigal Kerszenbaum

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Preface xix

Acknowledgments xxiii

I THEORY, CONSTRUCTION, AND OPERATION

1 Principles of Operation of Synchronous Machines 31.1 Introduction to Basic Notions on Electric Power 3

1.1.1 Magnetism and Electromagnetism 31.1.2 Electricity 6

1.2 ElectricalMechanical Equivalence 71.3 Alternating Current (ac) 81.4 Three-Phase Circuits 151.5 Basic Principles of Machine Operation 16

1.5.1 Faradays Law of Electromagnetic Induction 181.5.2 AmpereBiotSavarts Law of Electromagnetic 18

Induced Forces1.5.3 Lenzs Law of Action and Reaction 181.5.4 Electromechanical Energy Conversion 20

1.6 The Synchronous Machine 211.6.1 Background 211.6.2 Principles of Construction 241.6.3 Rotor Windings 261.6.4 Stator Windings 28

1.7 Basic Operation of the Synchronous Machine 301.7.1 No-Load Operation 321.7.2 Motor Operation 341.7.3 Generator Operation 351.7.4 Equivalent Circuit 351.7.5 Machine Losses 36Additional Reading 38

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CONTENTS

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2 Generator Design and Construction 392.1 Stator Core 412.2 Stator Frame 462.3 Flux and Armature Reaction 482.4 Electromagnetics 512.5 End-Region Effects and Flux Shielding 562.6 Stator Core and Frame Forces 622.7 Stator Windings 632.8 Stator Winding Wedges 732.9 End-Winding Support Systems 762.10 Stator Winding Configurations 772.11 Stator Terminal Connections 802.12 Rotor Forging 812.13 Rotor Winding 892.14 Rotor Winding Slot Wedges 952.15 Amortisseur Winding 962.16 Retaining Rings 972.17 Bore Copper and Terminal Connectors 1052.18 Slip-Collector Rings and Brush Gear 1062.19 Rotor Shrink Coupling 1072.20 Rotor Turning Gear 1082.21 Bearings 1092.22 Air and Hydrogen Cooling 1112.23 Rotor Fans 1122.24 Hydrogen Containment 1132.25 Hydrogen Coolers 118

References 118

3 Generator Auxiliary Systems 1213.1 Lube-Oil System 1223.2 Hydrogen Cooling System 1223.3 Seal-Oil System 1253.4 Stator Cooling Water System 128

3.4.1 System Components 1283.4.2 Stator Cooling Water Chemistry 1323.4.3 Stator Cooling Water System Conditions 134

3.5 Exciter Systems 1363.5.1 Types of Excitation Systems 1373.5.2 Excitation System Performance Characteristics 1393.5.3 Voltage Regulators 141

4 Operation and Control 1434.1 Basic Operating Parameters 143

4.1.1 Machine Rating 1444.1.2 Apparent Power 145

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4.1.3 Power Factor 1464.1.4 Real Power 1494.1.5 Terminal Voltage 1494.1.6 Stator Current 1494.1.7 Field Voltage 1504.1.8 Field Current 1504.1.9 Speed 1504.1.10 Hydrogen Pressure 1524.1.11 Hydrogen Temperature 1524.1.12 Short-Circuit Ratio 1534.1.13 Volts per Hertz and Overfluxing Events 153

4.2 Operating Modes 1604.2.1 Shutdown 1604.2.2 Turning Gear 1604.2.3 Run-up and Run-Down 1624.2.4 Field Applied Offline (Open Circuit) 1634.2.5 Synchronized and Loaded (Online) 1634.2.6 Start-up Operation 1634.2.7 Online Operation 1634.2.8 Shutdown Operation 165

4.3 Machine Curves 1654.3.1 Open-Circuit Saturation Characteristic 1654.3.2 Short-Circuit Characteristic 1654.3.3 Capability Curves 1674.3.4 V-Curves 169

4.4 Special Operating Conditions 1704.4.1 Unexcited Operation (Loss-of-Field Condition) 1704.4.2 Negative-Sequence Currents 1744.4.3 Off-Frequency Currents 1754.4.4 Load Cycling and Repetitive Starts 1774.4.5 Overloading 1784.4.6 Extended Turning-Gear Operation 1784.4.7 Loss of Cooling 1814.4.8 Overfluxing 1824.4.9 Overspeed 1904.4.10 Loss of Lubrication Oil 1904.4.11 Out-of-Step Synchronization and Near Short Circuits 1914.4.12 Ingression of Cooling Water and Lubricating Oil 1924.4.13 Under- and Overfrequency Operation (U/F and O/F) 193

4.5 Basic Operation Concepts 1934.5.1 Steady-State Operation 1934.5.2 Equivalent Circuit and Vector Diagram 1964.5.3 Power Transfer Equation between Alternator and 196

Connected System4.5.4 Working with the Fundamental Circuit Equation 198

CONTENTS ix

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4.5.5 Parallel Operation of Generators 2034.5.6 Stability 2064.5.7 Sudden Short Circuits 211

4.6 System Considerations 2134.6.1 Voltage and Frequency Variation 2144.6.2 Negative-Sequence Current 2144.6.3 Overcurrent 2244.6.4 Current Transients 2244.6.5 Overspeed 224

4.7 Grid-Induced Torsional Vibrations 2244.7.1 Basic Principles of Shaft Torsional Vibration 2244.7.2 Spring Model of a Turbo-Generator Shaft Train 2264.7.3 Determination of Shaft Torque and Shaft Torsional Stress 2294.7.4 Material Changes due to Torsional Vibrations 2294.7.5 Types of Grid-Induced Events 2294.7.6 Monitoring of Torsional Vibration Events 2344.7.7 Industry Experience and Alleviation Techniques 236

4.8 Excitation and Voltage Regulation 2374.8.1 The Exciter 2374.8.2 Excitation Control 238

4.9 Performance Curves 2384.9.1 Losses Curves 2384.9.2 Efficiency Curve 239

4.10 Sample of Generator Operating Instructions 239References 250

5 Monitoring and Diagnostics 2515.1 Generator Monitoring Philosophies 2525.2 Simple Monitoring with Static High-Level Alarm Limits 2535.3 Dynamic Monitoring with Load-Varying Alarm Limits 2545.4 Artificial Intelligence Diagnostic Systems 2575.5 Monitored Parameters 260

5.5.1 Generator Electrical Parameters 2615.5.2 Stator Core and Frame 2655.5.3 Stator Winding 2765.5.4 Rotor 2935.5.5 Excitation System 3135.5.6 Hydrogen Cooling System 3155.5.7 Lube-Oil System 3195.5.8 Seal-Oil System 3215.5.9 Stator Cooling Water System 324

References 330

6 Generator Protection 3336.1 Basic Protection Philosophy 3336.2 Generator Protective Functions 334

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6.3 Brief Description of Protective Functions 3376.3.1 Synchronizer and Sync-Check Relays (Functions 15 339

and 25)6.3.2 Short-Circuit Protection (Functions 21, 50, 51,51V, 339

and 87)6.3.3 Volts/Hertz Protection (Function 24) 3416.3.4 Over- and Undervoltage Protection (Functions 59 342

and 27)6.3.5 Reverse Power Protection (Function32) 3436.3.6 Loss-of-Field Protection (Function 40) 3456.3.7 Stator Unbalanced Current Protection (Function 46) 3456.3.8 Stator and Rotor Thermal Protection (Function 49) 3476.3.9 Voltage Balance Protection (Function 60) 3486.3.10 Time Overcurrent Protection for Detection of 349

Turn-to-Turn Faults (Function 61)6.3.11 Breaker Failure Protection (Function 62B) 3506.3.12 Rotor Ground-Fault Protection (Function 64F) 3516.3.13 Over-/Underfrequency Protection (Function 81) 3526.3.14 Out-of-Step Operation (Loss of Synchronism) 353

(Function 78)6.4 Specialized Protection Schemes 355

6.4.1 Protection Against Accidental Energization 3556.4.2 dc Field Ground Discrimination 3576.4.3 Vibration Considerations 3606.4.4 Operation of the Isolated-Phase Bus (IPB) at Reduced 362

Cooling and Risks from H2 Leaks into the IPB6.4.5 Calculation of the H2 Mix in the IPB for a Given H2 364

Leak from the Generator into the IPB6.5 Tripping and Alarming Methods 367

References 372

II INSPECTION, MAINTENANCE, AND TESTING

7 Inspection Practices and Methodology 3757.1 Site Preparation 375

7.1.1 Foreign Material Exclusion 3757.1.2 Foreign Material Exclusion - Procedures 383

7.2 Experience and Training 3847.3 Safety ProceduresElectrical Clearances 3847.4 Inspection Frequency 3877.5 Generator Accessibility 3887.6 Inspection Tools 3897.7 Inspection Forms 394

References 409

CONTENTS xi

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8 Stator Inspection 4118.1 Stator Frame and Casing 412

8.1.1 External Components 4128.1.2 Internal Components 4238.1.3 Caged Stator CoresInspection and Removal 435

8.2 Stator Core 4388.2.1 Stator Bore Contamination 4388.2.2 Blocked Cooling Vent Ducts 4408.2.3 Iron Oxide Deposits 4408.2.4 Loose Core Iron/Fretting and Interlaminar Failures 4438.2.5 Bent/Broken Laminations in the Bore 4558.2.6 Space Block Support and Migration 4608.2.7 Migration of Broken Core Plate and Space Block 461

Thick Plates8.2.8 Laminations Bulging into Air Vents 4618.2.9 Greasing/Oxide Deposits on Core Bolts 4628.2.10 Core-Compression Plates 4648.2.11 Core-End Flux Screens and Flux Shunts 4658.2.12 Frame-to-Core Compression (Belly) Bands 4678.2.13 Back-of-Core Burning 4678.2.14 Core-End Overheating 470

8.3 Stator Windings 4738.3.1 Stator Bar/Coil Contamination (Cleanliness) 4738.3.2 End-Winding Blocking and Roving 4748.3.3 Surge-Rings 4788.3.4 Surge-Ring Insulation Condition 4808.3.5 End-Winding Support Structures 4818.3.6 Ancillary End-Winding Support Hardware 4848.3.7 Asphalt Bleeding/Soft Spots 4878.3.8 Tape Separation/Girth Cracking 4898.3.9 Insulation Galling/Necking beyond the Slot 4928.3.10 Insulation Bulging into Air Ducts 4928.3.11 Insulation Condition, Overheating, and Electrical Aging 4938.3.12 Corona Activity 4968.3.13 Stator Wedges 5048.3.14 End-Wedge Migration Out of Slot 5078.3.15 Side-Packing Fillers 5088.3.16 Leaks in Water-Cooled Stator Windings 5098.3.17 Magnetic Termites 5128.3.18 Flow Restriction in Water-Cooled Stator Windings 5158.3.19 Hoses, Gaskets, and O-Rings in Water-Cooled 518

Stator Windings8.4 Phase Connectors and Terminals 520

8.4.1 Circumferential Bus Insulation 5208.4.2 Phase Droppers 523

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8.4.3 High-Voltage Bushings 5258.4.4 Standoff Insulators 5268.4.5 Bushing Vents 5278.4.6 Bushing-Well lnsulators and Hydrogen Sealant Condition 5288.4.7 Generator Current Transformers (CTs) 529

8.5 Hydrogen Coolers 532References 534Additional Reading 535

9 Rotor Inspection 5379.1 Rotor Cleanliness 5389.2 Retaining Rings 539

9.2.1 Nonmagnetic 185 and 1818 Retaining Rings 5459.2.2 Removal of Retaining Rings 546

9.3 Fretting/Movement at Interference Fit Surfaces of Wedges and Rings 5549.3.1 Tooth Cracking 554

9.4 Centering (Balance) Rings 5639.5 Fan Rings or Hubs 5639.6 Fan Blades 5659.7 Bearings and Journals 5679.8 Balance Weights and Bolts 5709.9 End Wedges and Damper Windings 5719.10 Other Wedges 5769.11 WindingsGeneral 577

9.11.1 Conductor Material 5789.12 Rotor WindingsSlot Region 580

9.12.1 Slot Liner 5809.12.2 Turn Insulation 5839.12.3 Creepage Block and Top Channel 5879.12.4 C-Channel Subslot 589

9.13 End Windings and Main Leads 5899.13.1 Retaining Ring Liners 5929.13.2 End Turns and Blocking 5949.13.3 Shorted Turns 6009.13.4 Top-Tooth Cracking 6039.13.5 dc Main Leads 6039.13.6 Coil and Pole Connections 607

9.14 Collector Rings 6139.15 Collector Ring Insulation 6199.16 Bore Copper and Radial (Vertical) Terminal Stud Connectors 6219.17 Brush-Spring Pressure and General Condition 6249.18 Brush Rigging 6269.19 Shaft Voltage Discharge (Grounding) Brushes 6299.20 Rotor Winding Main Lead Hydrogen SealingInner and Outer 6309.21 Circumferential Pole Slots (Body Flex Slots) 633

CONTENTS xiii

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9.22 Blocked Rotor Radial Vent HolesShifting of Winding and/or 635Insulation

9.23 Couplings and Coupling Bolts 6369.24 Bearing Insulation 6389.25 Hydrogen Seals 640

9.25.1 Journal Seals 6419.25.2 Thrust-Collar Seals 6429.25.3 Carbon Seals 645

9.26 Rotor-Body Zone Rings 6469.27 Rotor Removal 648

References 657

10 Auxiliaries Inspection 65910.1 Lube-Oil System 65910.2 Hydrogen Cooling System 660

10.2.1 Hydrogen Desiccant/Dryer 66110.3 Seal-Oil System 66210.4 Stator Cooling Water System 66310.5 Exciters 666

10.5.1 Rotating Systems Inspection 66610.5.2 Static Systems Inspection 66610.5.3 Brushless Systems Inspection 66710.5.4 Specific Inspection Items 667

11 Generator Maintenance Testing 67311.1 Stator Core Mechanical Tests 673

11.1.1 Core Tightness 67311.1.2 Core and Frame Vibration Testing 674

11.2 Stator Core Electrical Tests 67611.2.1 EL CID Testing 67611.2.2 Rated Flux Test with Infrared Scan 68411.2.3 Core Loss Test 69511.2.4 Through-Bolt Insulation Resistance 69611.2.5 Insulation Resistance of Flux Screens 696

11.3 Stator Winding Mechanical Tests 69611.3.1 Wedge Tightness 69611.3.2 Stator End-Winding Vibration 700

11.4 Water-Cooled Stator Winding Tests 70011.4.1 Air Pressure Decay 70011.4.2 Tracer Gases 70111.4.3 Vacuum Decay 70111.4.4 Pressure Drop 70211.4.5 Flow Testing 70211.4.6 Capacitance Mapping 702

11.5 Stator Winding Electrical Tests 702

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11.5.1 Pretesting Requirements 70311.5.2 Series Winding Resistance 70411.5.3 Insulation Resistance (IR) 70411.5.4 Polarization Index (PI) 70611.5.5 Dielectric Absorption during dc Voltage Application 70811.5.6 dc Leakage or Ramped Voltage 70811.5.7 dc Hi-Pot 71011.5.8 ac Hi-Pot 71011.5.9 Partial Discharge (PD) Off-line Testing 71411.5.10 Capacitance Measurements 71711.5.11 Dissipation/Power Factor Testing 71711.5.12 Dissipation/Power Factor Tip-up Test 717

11.6 Rotor Mechanical Testing 71811.6.1 Rotor Vibration 71811.6.2 Rotor Nondestructive Examination Inspection 719

Techniques11.6.3 Some Additional Rotor NDE Specifics 72711.6.4 Air Pressure Test of Rotor Bore 731

11.7 Rotor Electrical Testing 73311.7.1 Winding Resistance 73311.7.2 Insulation Resistance (IR) 73311.7.3 Polarization Index (PI) 73311.7.4 dc Hi-Pot 73411.7.5 ac Hi-Pot 73411.7.6 Shorted Turns DetectionGeneral 73411.7.7 Shorted Turns Detection by Recurrent Surge Oscillation 736

(RSO)11.7.8 Shorted Turns Detection by Open-Circuit Test 73711.7.9 Shorted Turns Detection by Winding Impedance 74111.7.10 Shorted Turns Detection by Low-Voltage dc or Volt 742

Drop11.7.11 Shorted Turns Detection by Low-Voltage ac or C 743

Core Test11.7.12 Shorted Turns Detection by Shorted Turns Detector 744

(Flux Probe)11.7.13 Field-Winding Ground Detection by the Split-Voltage 762

Test11.7.14 Field Ground Detection by the Current-through-Forging 762

Test11.7.15 Shaft Voltage and Grounding 765

11.8 Hydrogen Seals 76511.8.1 NDE 76511.8.2 Insulation Resistance 766

11.9 Bearings 76611.9.1 NDE 766

CONTENTS xv

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11.9.2 Insulation Resistance 76611.10 Thermal Sensitivity Testing and Analysis 767

11.10.1 Background 76711.10.2 Typical Thermal Sensitivity Test 769

11.11 Heat-Run Testing 77111.11.1 Test Procedure 77111.11.2 Acceptance Parameters 772

11.12 Hydrogen Leak Detection 77311.12.1 Pressure Drop 77411.12.2 SF6 77611.12.3 Helium 77711.12.4 Snoop 77711.12.5 Ultrasonic 777References 777

12 Maintenance 77912.1 General Maintenance Philosophies 779

12.1.1 Breakdown Maintenance 78012.1.2 Planned Maintenance 78112.1.3 Predictive Maintenance 78212.1.4 Condition-Based Maintenance (CBM) 782

12.2 Operational and Maintenance History 78312.3 Maintenance Intervals/Frequency 78312.4 Type of Maintenance 784

12.4.1 Extent of Maintenance 78412.4.2 Repair or Replacement 78612.4.3 Rehabilitation/Upgrading/Uprating 78712.4.4 Obsolescence 789

12.5 Work Site Location 79112.5.1 Transportation 791

12.6 Workforce 79212.7 Spare Parts 79512.8 Uprating 796

12.8.1 Drivers for Uprating 79612.8.2 Uprating Considerations 79812.8.3 Component Evaluations 80012.8.4 Reliability and Effect of Uprating on Generator Life 80412.8.5 Required Inspection and Tests Prior to Uprating 80612.8.6 Required Maintenance Prior to Uprating 80712.8.7 Heat-Run Testing After Uprating 80812.8.8 Maintenance Schedule After Uprating 810

12.9 Long-Term Storage and Mothballing 81012.9.1 Reasons for Storage of Generator Equipment 81012.9.2 General Requirements 81112.9.3 Storage Requirements 812

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12.9.4 Monitoring and Maintenance During Storage 81812.9.5 Restoration from Storage 82012.9.6 Long Term Storage Maintenance Procedures and 822

Testing12.10 Life Cycle Management (LCM) 82512.11 Single Point Vulnerability (SPV) Analysis 827

References 828

Index 829

CONTENTS xvii

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It is not uncommon for a large utility to have units of disparate size, origin, and vintagein its fleet of generators. Among its dozens of generators, there might be some fromthe 1950s or 1960s and some with their original asphalt or thermoplastic windings.These, and later units, may be running with and without magnetic retaining rings.Some might have thermoelastic windings of all sorts, with or without asbestos; theymight be hydrogen-cooled or air-cooled, have split-stator windings, be self-excited ordifferent types of externally excited, steam-driven or combustion-driven, and the listgoes on and on. Now, take that diversity and include units operating in 50 and 60 Hzgrids, built by Western, Asian, and Eastern European manufacturers to different stan-dards. This is what you may find in some of the new independent, deregulated powerproducers that, in addition to building new plants, have purchased entire fleets of olderunits in several countries around the globe.

The reasons why one may find so many old units still in operation are not diffi-cult to discern. First of all, a typical generator is made with an intent to last no less than30 years or so. Second, replacing an operating unit is very capital intensive and, thus,done only when a catastrophic failure has occurred or some other major failure of themachine that renders continuous operation not economically viable. Third, althoughexpected to last 30 years, large turbogenerators are known to have their lives extendedfar beyond that, if well maintained and operated. Sometimes that also requires replac-ing a major component, such as the armature winding and/or a rotor winding (or theentire rotor!). Significant changes in design tend to occur every few years, for differentcomponents. For instance, a history of the insulation systems encountered in genera-tors shows that every few years there is some big change resulting in increased ratings.These changes typically derive from the adoption of a new materials such as thechange from magnetic to nonmagnetic material for retaining rings. Not all changes arealways positive. Some new designs end up being reversed or revised after experienceunmasks significant defects in them.

There are countless scraps of information about the operation, maintenance, andtroubleshooting of large turbogenerators in many publications. All vendors at onestage or another have produced and published interesting literature about the operationof their generators. In particular, the technical information letters put out by somemanufacturers (called different names by different vendors) offer a wealth of detailed

xix

PREFACE

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O&M topics. Institutions such as EPRI in the United States, CIGRE, IEC, ANSI,IEEE, and other national standards cover various aspects of the operation and mainte-nance of generators in general, but offer no specifics that may help troubleshoot a par-ticular unit. It is difficult to obtain from those sources a condensed and operational setof insights useful to the solution of a given problem with a specific machine. It is nowonder then that with so many dissimilar units in operation and such a variegated ex-perience, we are often forced to call the experts, who tend to be folks almost as oldas the oldest units in operation. These are individuals who have crawled, inspected,tested, and maintained many diverse generators over the years. In doing so, they haveretained knowledge about the different design, material, and manufacturing character-istics, typical problems, and most effective solutions. This type of expertise cannot belearned in a classroom.

Unfortunately, not every company retains an individual with the breadth and depthof expertise required for troubleshooting all its units. In fact, with the advent of dereg-ulation, many small nonutility (third-party) power producers operate small fleets ofgenerators without the benefit of in-house expertise. In lieu of that, they depend heavi-ly on OEMs and independent consultants. Large utilities in many places have also seentheir expertise dissipate, not to a small extent because of a refocus of management pri-orities. All these developments are occurring at the same time that these units arecalled to operate in a more onerous environment. Economic dispatch in a deregulatedor semideregulated world results in an increased use of double-shifting and load-cycling.

Some effort has been made over the years to capture the experts knowledge andmake it readily available to any operator. This effort took the shape of expert systems.However, adaptation of these computer programs to the many different types of gener-ators and associated equipment in existence has proved to be the Achilles heel of thistechnology.

This book is designed to partially fill the gap by offering a comprehensive view ofthe many issues related to the operation, inspection, maintenance, and troubleshootingof large turbine generators. The contents of this second edition have been significantlyenhanced and many new additional topics included. All of the information in the bookis the result of many years of combined hands-on experience of the authors. It waswritten with the machines operator and inspector in mind, as well as providing a guideto uprating and life enhancement of large generators. Although not designed to providea step-by-step guide for the troubleshooting of large generators, it serves as a valuablesource of information that may prove to be useful during troubleshooting activities.The topics covered are also cross-referenced to other sources. Many such referencesare included to facilitate those readers interested in enlarging their knowledge of a spe-cific issue under discussion. For the most part, theoretical equations have been left out,as there are several exceptionally good books on the theory of operation of synchro-nous machines. Those readers who so desire can readily access those books. Severalreferences are cited. This book, however, is about the practical aspects that character-ize the design, operation, and maintenance of large turbine-driven generators, and asignificant number of practical calculations used commonly in maintenance and test-ing situations have been added.

xx PREFACE

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Chapter 1 (Principles of Synchronous Machines) provides a basis of theory forelectricity and electromagnetism upon which the machines covered in this book arebased. As well, the fundamentals of synchronous machine construction and operationare also discussed. This is for the benefit of generator operators who have a mechanicsbackground and are inclined to attain a modicum of proficiency in understanding thebasic principles of operation of the generator. It also comes in handy for those profes-sors who would like to adopt this book as a reference for a course on large rotatingelectric machinery.

Chapters 2 and 3 (Generator Design and Construction and Generator AuxiliarySystems) contain a very detailed and informative description of all the componentsfound in a typical generator and its associated auxiliary systems. Described therein arethe functions that the components perform, as well as all relevant design and opera-tional constrains. Some additional insight into design methods and calculations arealso provided.

Chapter 4 (Operation and Control) introduces the layperson to the many opera-tional variables that describe a generator. Most generatorgrid interaction issues andtheir affect on the machine components and operation are covered in great detail.

Chapter 5 (Monitoring and Diagnostics) and Chapter 6 (Generator Protection)serve to introduce all aspects related to the on-line and off-line monitoring and protec-tion of a large turbogenerator. Although not intended to serve as a guideline for de-signing and setting up the protection systems of a generator, they provide a wealth ofbackground information and pointers to additional literature.

Chapters 7 (Inspection Practices and Methodology), leads off the second part ofthe book with a look at preparing for a hands-on inspection of large generators. Thechapter discusses the issues of concern for both safety of personnel and the equipmentas well as the types of tools and approaches used in inspecting large generators. Thischapter also contains a collection of most inspection forms typically used for inspect-ing turbogenerators. These forms are very useful and can be readily adapted to any ma-chine and plant.

Chapter 8 (Stator Inspection), Chapter 9 (Rotor Inspection), and Chapter 10(Auxiliaries Inspection) constitute the core of this book. They describe all compo-nents presented in Chapters 2 and 3, but within the context of their behavior under realoperational constraints, modes of failure, and typical troubleshooting activities. Thesechapters provide detailed information on what to look for, and how to recognize prob-lems in the machine during inspection. Chapters 8 and 9 also contain some basic for-mulas and procedures for some of the various activities that occur during inspection,maintenance, and testing of large generators.

Chapter 11 (Generator Maintenance Testing) contains a comprehensive summaryof the many techniques used to test the many components and systems comprising agenerator. The purpose of the descriptions is not to serve as a guide to performing thetests-there are well-established guides and standards for thatrather, they are intendedto illustrate the palette of possible tests to choose from. Provided as well is a succinctexplanation of the character of each test and explanations of how they are carried out.

Chapter 12 (Maintenance Philosophies) is included to provide some perspectiveto the reader on the many choices and approaches that can be taken in generator and

PREFACE xxi

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auxiliary systems maintenance. Often, there are difficult decisions on how far to takemaintenance. In some cases, only basic maintenance may be required, and on other oc-casions it may be appropriate to carry out extensive rehabilitation of existing equip-ment or even replacement of components. This chapter discusses some of the issuesthat need to be considered when deciding on what, how much, and where to do it.Along with the regular maintenance aspects, other important issues like uprating andlong-term storage are also addressed.

We hope that this book will be not only useful to the operator in the power plant butalso to the design engineer and the systems operations engineer. We have provided awealth of information obtained in the field about the behavior of such machines, in-cluding typical problems and conditions of operation. The book should also be usefulto the student of electrical rotating machines as a complementary reference to thebooks on machine theory.

Although we have tried our best to cover each topic as comprehensively as possible,the book should not be seen as a guide to troubleshooting. In each case in which a realproblem is approached, a whole number of very specific issues only relevant to thatvery unique machine come into play. These can never be anticipated or known andthus described in a book. Thus, we recommend the use of this book as a general refer-ence source, but that the reader should always obtain adequate on-the-spot expertisewhen approaching a particular problem.

We remain intent on updating the contents of this book from time to time, from ourown experience as well as from that of others. Therefore, we would welcome from thereaders their comments, which they can submit to the publisher, for incorporation infuture editions.

GEOFF KLEMPNERISIDOR KERSZENBAUM

Toronto, Ontario, Canada Irvine, CaliforniaAugust 2008

xxii PREFACE

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The contents of this book are impossible to learn in a class. They are the result of per-sonal experience accumulated over years of working with large turbine-driven genera-tors. Most of all, they are the result of the invaluable long-term contribution ofcoworkers and associates. Each author was motivated by an important individual at anearly stage of his career, and by many outstanding individuals in the profession oversubsequent years. Attempting to mention all these people would lead to the unintendedomission of some.

The authors are most indebted to the IEEE Press for reviewing the second editionproposal and supporting its publication. They also wish to express their sincere grati-tude to the technical reviewers, Robert Hindmarsh and Nils Nilsson, for painstakinglyreviewing the final manuscript and making numerous useful remarks. The authors alsowould like to thank the members of the editorial departments of the IEEE Press andJohn Wiley & Sons, the reviewers, and all others involved in the publication of thisbook for their support in making its publication possible.

Finally, but certainly most intensely, the authors wish to thank their immediate fam-ilies for their continuous support and encouragement.

G.K.I.K.

xxiii

ACKNOWLEDGMENTS

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I

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The synchronous electrical generator (also called alternator) belongs to the family ofelectric rotating machines. Other members of the family are the direct-current (dc) mo-tor or generator, the induction motor or generator, and a number of derivatives of allthese three. What is common to all the members of this family is that the basic physicalprocess involved in their operation is the conversion of electromagnetic energy to me-chanical energy, and vice versa. Therefore, to comprehend the physical principles gov-erning the operation of electric rotating machines, one has to understand some rudi-ments of electrical and mechanical engineering.

Chapter 1 is written for those who are involved in operating, maintaining, and trou-ble-shooting electrical generators, and who want to acquire a better understanding ofthe principles governing the machines design and operation, but who do not have anelectrical engineering background. The chapter starts by introducing the rudiments ofelectricity and magnetism, quickly building up to a description of the basic laws ofphysics governing the operation of the synchronous electric machine, which is the typeof machine to which all turbogenerators belong.

1.1 INTRODUCTION TO BASIC NOTIONS ON ELECTRIC POWER

1.1.1 Magnetism and Electromagnetism

Certain materials found in nature exhibit a tendency to attract or repel each other.These materials, called magnets, are also called ferromagnetic because they includethe element iron as one of their constituent elements.

Handbook of Large Turbo-Generator Operations and Maintenance. By Klempner and Kerszenbaum 3Copyright 2008 The Institute of Electrical and Electronics Engineers, Inc.

1

PRINCIPLES OF OPERATION OF

SYNCHRONOUS MACHINES

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Magnets always have two poles: one called north, the other called south. Two northpoles always repel each other, as do two south poles. However, north and south polesalways attract each other. A magnetic field is defined as a physical field established be-tween two poles. Its intensity and direction determine the forces of attraction or repul-sion existing between the two magnets.

Figures 1.1 and 1.2 are typical representations of two interacting magnetic polesand the magnetic field established between them.

Magnets are found in nature in all sorts of shapes and chemical constitution. Mag-nets used in industry are artificially made. Magnets that sustain their magnetism forlong periods of time are denominated permanent magnets. The magnetic field pro-duced by the north and the south pole of a permanent magnet is directional from northto south (see Fig. 1.3). These are widely used in several types of electric rotating ma-

4 PRINCIPLES OF OPERATION OF SYNCHRONOUS MACHINES

Fig. 1.1 Schematic representation of two magnetic poles of opposite polarity, withthe magnetic field between them shown as lines of force.

Fig. 1.2 Schematic representation of two north poles and the magnetic field betweenthem. South poles will create similar field patterns, but the lines of force will point to-ward the poles.

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