ELECTRICAL INSULATION FOR ROTATING MACHINES

Transcription

1 ELECTRICAL INSULATION FOR ROTATING MACHINES Design, Evaluation, Aging, Testing, and Repair Second Edition GREG C. STONE IAN CULBERT EDWARD A. BOULTER HUSSEIN DHIRANI p(ji!i gm S mmoi 0N POWER ENGINEERING IEEE PRESS Wiley

2 CONTENTS PREFACE xix CHAPTER 1 ROTATING MACHINE INSULATION SYSTEMS Types of Rotating Machines AC Motors Synchronous Generators Induction Generators Permanent Magnet (PM) Synchronous Classification by Cooling Winding Components Stator Winding Insulated Rotor Windings 10 l.2.3 Squirrel Cage Induction Motor Rotor Windings Types of Stator Winding Construction Random-Wound Stators Form-Wound Stators Coil Type Form-Wound Stators Roebel Bar Type Form-Wound Stator Winding Insulation System Features Strand Insulation Turn Insulation Groundwall Insulation Groundwall Partial Discharge Suppression 21 Motors and Generators Groundwall Stress Relief Coatings for Conventional Stators Surface Stress Relief Coatings for Inverter-Fed Stators Conductor Shields Mechanical Support in the Slot Mechanical Support in the End winding Transposition Insulation Random-Wound Stator Winding Insulation System Features Partial Discharge Suppression in Inverter-Fed Random Windings Rotor Winding Insulation System Components Salient Pole Rotor Round Rotors 41 l.6.3 Induction Machine Wound Rotors 43 References 45 CHAPTER 2 EVALUATING INSULATION MATERIALS AND SYSTEMS Aging Stresses Thermal Stress 49 V

3 Vi CONTENTS Electrical Stress Ambient Stress (Factors) Mechanical Stress Radiation Stress Multiple Stresses Principles of Accelerated Aging Tests Candidate and Reference Materials/Systems Statistical Variation Failure Indicators Thermal Endurance Tests Basic Principles Thermal Identification and Classification Insulating Material Thermal Aging Test Standards Insulation System Thermal Aging Test Standards Future Trends Electrical Endurance Tests Proprietary Tests for Form-Wound Coils Standardized AC Voltage Endurance Test Methods for Form-Wound Coils/Bars Voltage Endurance Tests for Inverter-Fed Windings Thermal Cycling Tests IEEE Thermal Cycling Test IEC Thermal Cycling Test Nuclear Environmental Qualification Tests Environmental Qualification (EQ) by Testing Environmental Qualification by Analysis Environmental Qualification by a Combination of Testing and Analysis Multifactor Stress Testing Material Property Tests 78 References 80 CHAPTER 3 HISTORICAL DEVELOPMENT OF INSULATION MATERIALS AND SYSTEMS Natural Materials for Form-Wound Stator Coils Early Synthetics for Form-Wound Stator Coils Plastic Films and Non-Wovens Liquid Synthetic Resins Mica Polyesters Epoxides (Epoxy Resins) Mica Splittings Mica Paper Mica Backing Materials Glass Fibers Laminates Evolution of Wire and Strand Insulations Manufacture of Random-Wound Stator Coils Manufacture of Form-Wound Coils and Bars 103

4 CONTENTS VII Early Systems Asphaltic Mica Systems Individual Coil and Bar Thermoset Systems Global VPI Systems Wire Transposition Insulation Methods of Taping Stator Groundwall Insulation Insulating Liners, Separators, and Sleeving Random-Wound Stators Rotors 110 References 110 CHAPTER 4 STATOR WINDING INSULATION SYSTEMS IN CURRENT USE in 4.1 Consolidation of Major Manufacturers Description of Major Trademarked Form-Wound Stator Insulation Systems Westinghouse Electric Co.: Thermalastic General Electric: Micapals I and II, Epoxy Mica Mat, Micapal HT and Hydromat Alsthom, GEC Alsthom, and Alstom Power: lsotenax, Resitherm, Resiflex, Resivac, and Duritenax Siemens AG, KWU: Micalastic Brown Boveri, ASEA, ABB, and Alstom Power: Micadur, Micadur Compact, Micapac, and Micarex Toshiba Corporation: Tosrich and Tostight Mitsubishi Electric Corporation Hitachi, Ltd.: Hi-Resin, Hi-Mold, and Super Hi-Resin Dongfang Electric Machinery Harbin Electric Corporation (HEC) Shanghai Electric Machinery Jinan Power Equipment: Resitherm, Micadur, and Micadur Compact Summary of Present-Day Insulation Systems Recent Developments for Form-Wound Insulation Systems Reducing Groundwall Thermal Impedance Increasing Electric Stress Environmental Issues Random-Wound Stator Insulation Systems Magnet Wire Insulation Phase and Ground Insulation Varnish Treatment and Impregnation 128 References 129 CHAPTER 5 ROTOR WINDING INSULATION SYSTEMS Rotor Slot and Turn Insulation Collector Insulation End Winding Insulation and Blocking Retaining Ring Insulation Direct-Cooled Rotor Insulation Wound Rotors 139

5 Viii CONTENTS 5.7 Superconducting Sychronous Rotors 140 References 141 CHAPTER 6 ROTOR AND STATOR LAMINATED CORES Magnetic Materials Magnetic Fields Ferromagnetism Magnetization Saturation Curve Ferromagnetic Materials Permeability Hysteresis Loss Eddy Current Loss Other Factors Affecting Core Loss Effect of Direction of the Grain Effect of Temperature Effect of Heat Treatment Effect of Impurities and Alloying Elements Silicon/Aluminum Steels Mill-Applied Insulation Lamination Punching and Laser Cutting Annealing and Burr Removal Enameling or Film Coatings Stator and Rotor Core Construction Stator Core Construction: General Hydrogenerator and Large Motor Stator Core Assembly and Support Turbogenerator Stator Core Assembly and Support Smaller Motor and Generator Stator Cores Rotor Core Construction 155 References 157 CHAPTER 7 GENERAL PRINCIPLES OF WINDING FAILURE, REPAIR AND REWINDING Failure Processes Relative Failure Rates of Components Factors Affecting 7.2 Factors Affecting Repair Decisions 164 Failure Mechanism Predominance Rapid Repair of Localized Stator Winding Damage Cutting out Stator Coils After Failure Bar/Coil Replacement and Half Coil Splice Rewinding 168 References 169 CHAPTER 8 STATOR FAILURE MECHANISMS AND REPAIR Thermal Deterioration General Process Root Causes 174

6 CONTENTS ix Symptoms Remedies Thermal Cycling General Process Root Causes Symptoms Remedies Inadequate Resin Impregnation or Dipping General Process Root Causes Symptoms Remedies Loose Coils in the Slot General Process Root Causes Symptoms Remedies Semiconductive Coating Failure General Process Root Causes Symptoms Remedies Semiconductive/Grading Coating Overlap Failure General Process Root Causes Symptoms Remedies High Intensity Slot Discharge General Process Root Causes Symptoms Repairs Vibration Sparking (Spark Erosion) General Process Root Cause Symptoms Repair Transient Voltage Surges General Process Root Causes Symptoms Remedies Repetitive Voltage Surges Due to Drives General Process Root Cause Symptoms Remedies Contamination (Electrical Tracking) General Process Root Causes 214

7 X CONTENTS Symptoms Remedies Abrasive Particles General Process Root Causes Symptoms and Remedies Chemical Attack General Process Root Causes Symptoms Remedies Inadequate End Winding Spacing General Process Root Causes Symptoms Remedies End Winding Vibration General Process Root Causes Symptoms Remedies Stator Coolant Water Leaks General Process Root Causes Symptoms Remedies Poor Electrical Connections GeneralProcess Root Causes Symptoms Remedies 233 References 233 CHAPTER 9 ROUND ROTOR WINDING FAILURE MECHANISMS AND REPAIR Thermal Deterioration GeneralProcess Root Cause Symptoms Thermal Cycling General Process Root Cause Symptoms Abrasion Due to Imbalance or Turning Gear Operation (Copper Dusting) GeneralProcess Root Causes Symptoms Pollution (Tracking) General Process Root Causes 245

8 CONTENTS Xi Common Symptoms Repetitive Voltage Surges General Process Root Causes Common Symptoms Centrifugal Force General Process Root Causes Common Symptoms Operating Without Field Current Loss of Field During Operation Inadvertent Closure of Generator Breaker Root Causes Common Symptoms Remedies 250 References 252 CHAPTER 10 SALIENT POLE ROTOR WINDING FAILURE MECHANISMS AND REPAIR Thermal Deterioration General Process Root Causes Common Symptoms Thermal Cycling General Process Root Causes Common Symptoms Pollution (Tracking and Moisture Absorption) General Process Root Causes Common Symptoms Abrasive Particles General Process Root Causes Common Symptom Centrifugal Force General Process Root Causes Common Symptoms Repetitive Voltage Surges General Process Root Causes Common Symptoms Salient Pole Repair 261 References 263 CHAPTER 11 WOUND ROTOR WINDING FAILURE MECHANISMS AND REPAIR Voltage Surges 266

9 xii CONTENTS General Process Root Causes Common Symptoms Unbalanced Stator Voltages General Process Root Causes Common Symptoms High Resistance Connections-Bar Lap and Wave Windings General Process Root Causes Common Symptoms End Winding Banding Failures General Process Root Causes Common Symptoms Slip Ring Insulation Shorting and Grounding General Process Root Causes Wound Rotor Winding Repair Failed Windings Contaminated Windings and Slip Ring Insulation Failed Connections in Bar-Type Windings Damaged End Winding Banding Failed or Contaminated Slip Ring Insulation 272 References 272 CHAPTER 12 SQUIRREL CAGE INDUCTIONROTOR WINDING FAILURE MECHANISMS AND REPAIR Thermal General Process Root Causes Common Symptoms Cyclic Mechanical Stressing General Process Root Causes Common Symptoms Poor Design/Manufacture General Process and Root Causes Common Symptoms Repairs 283 References 284 CHAPTER 13 CORE LAMINATION INSULATION FAILURE AND REPAIR Thermal Deterioration General Process Root Causes Common Symptoms Electrical Degradation 290

10 CONTENTS Xiii General Process Root Causes Common Symptoms Mechanical Degradation General Process Root Causes Symptoms Failures Due to Manufacturing Defects General Process Root Causes Symptoms Core Repairs Loose Cores Core Insulation Shorting Core Damage Due to Winding Electrical Faults False Tooth Cracked Through-Bolt Insulation Split Core Repairs 308 References 309 CHAPTER 14 GENERAL PRINCIPLES OF TESTING AND MONITORING Purpose of Testing and Monitoring Assessing Winding Condition and Remaining Winding Life Prioritizing Maintenance Commissioning and Warranty Testing Determining Root Cause of Failure Off-Line Testing Versus On-Line Monitoring Role of Visual Inspections Expert Systems to Convert Data Into Information 315 References 316 CHAPTER 15 OFF-LINE ROTOR AND STATOR WINDING TESTS Insulation Resistance and Polarization Index Purpose and Theory Test Method Interpretation DCHipotTest Purpose and Theory Test Method Interpretation Polarization/Depolarization Current (PDC) Purpose and Theory Test Method Interpretation DC Conductivity Purpose and Theory Test Method Interpretation 333

11 XIV CONTENTS 15.5 Poor Connection Hot Spot (High Current-Infrared Camera) Purpose and Theory Test Method Interpretation ACHipot Purpose and Theory Test Method Interpretation Capacitance Purpose and Theory Test Method Interpretation Stator Capacitance Tip-Up Purpose and Theory Test Method Interpretation Capacitive Impedance Test for Motor Stators Dissipation (or Power) Factor Purpose and Theory Test Method Interpretation Power (Dissipation) Factor Tip-Up Purpose and Theory Test Method Interpretation Off-Line Partial Discharge for Conventional Windings Purpose and Theory Test Method Interpretation Off-Line Partial Discharge for Inverter-Fed Windings Purpose and Theory Test Method and Interpretation Stator Blackout and Ultraviolet Imaging Purpose and Theory Test Method Interpretation Stator Partial Discharge Probe Purpose and Theory Test Method Interpretation Stator Surge Voltage Purpose and Theory Test Method Interpretation Inductive Impedance Semiconductive Coating Contact Resistance Purpose and Theory Test Method Interpretation Conductor Coolant Tube Resistance 369

12 CONTENTS XV Purpose and Test Method Stator Wedge Tap Purpose and Theory Test Method Interpretation Slot Side Clearance Purpose and Theory Test Method Interpretation Stator Slot Radial Clearance Purpose and Theory Test Method Interpretation Stator End Winding Bump Purpose and Theory Test Method Interpretation Stator Pressure and Vacuum Decay Purpose and Theory Test Methods and Interpretation Rotor Pole Drop (Voltage Drop) Purpose and Theory Test Method Salient Pole Rotor Test Method Round Rotors Interpretation Rotor RSO and Surge Purpose and Theory Test Method Interpretation Rotor Growler Purpose and Theory Test Method Interpretation Rotor Fluorescent Dye Penetrant Purpose and Theory Test Method and Interpretation Rotor Rated Flux Purpose and Theory Test Method Interpretation Rotor Single-Phase Rotation Purpose and Theory Test Method Interpretation 385 References 385 CHAPTER 16 IN-SERVICE MONITORING OF STATOR AND ROTOR WINDINGS Thermal Monitoring Stator Winding Point Sensors 390

13 XVI CONTENTS Rotor Winding Sensors Data Acquisition and Interpretation Thermography Condition Monitors and Tagging Compounds Monitoring Principles Interpretation Ozone Monitoring Principles Interpretation Online Partial Discharge Monitor Monitoring Principles Interpretation Online Capacitance and Dissipation Factor Monitoring Principle Data Acquisition and Interpretation Endwinding Vibration Monitor Monitoring Principles Data Acquisition and Interpretation Synchronous Rotor Flux Monitor Monitoring Principles Data Acquisition and Interpretation Current Signature Analysis Monitoring Principles Data Acquisition Interpretation Bearing Vibration Monitor Vibration Sensors Induction Motor Monitoring Synchronous Machine Monitoring Stator Winding Water Leak Monitoring 435 References 435 CHAPTER 17 CORE TESTING Knife Purpose and Theory Test Method Interpretation Rated Flux Purpose and Theory Test Method Interpretation Core Loss Purpose and Theory Test Method Interpretation Low Core Flux (El-CID) Purpose and Theory Test Method 453

14 CONTENTS XVli Interpretation 457 References 461 CHAPTER 18 NEW MACHINE WINDING AND REWIND SPECIFICATIONS Objective of Stator and Rotor Winding Specifications Trade-Offs Between Detailed and General Specifications General Items for Specifications Technical Requirements for New Stator Windings Technical Requirements for Insulated Rotor Windings New Round Rotor Windings Refurbishment and Replacement of Existing Round Rotor Windings New Salient Pole Windings Refurbishment and Repair of Existing Salient Pole Windings 484 References 486 CHAPTER 19 ACCEPTANCE AND SITE TESTING OF NEW WINDINGS Stator Winding Insulation System Prequalification Tests Dissipation Factor Tip-Up Partial Discharge Test for Conventional Windings Partial Discharge Test for Inverter Fed Windings Impulse (Surge) Voltage Endurance for Conventional Windings Voltage Endurance for Form-Wound Inverter Fed Windings Thermal Cycling Thermal Classification Stator Winding Insulation System Factory and On-Site Tests Insulation Resistance and Polarization Index Phase Resistance and/or Thermal Imaging ACandDCHipot Impulse (Surge) Strand-to-Strand Power Factor Tip-Up Partial Discharge Semiconductive Coating Test Wedge Tap Endwinding Bump Factory and On-Site Tests for Rotor Windings Tests Applicable to All Insulated Windings Round Rotor Synchronous Machine Windings Salient Pole Synchronous Machine Windings Wound Induction Rotor Windings Squirrel Cage Rotor Windings Core Insulation Factory and On-Site Tests Core Tightness Rated Flux Low Flux (El-CID) 506 References 506

15 xviii CONTENTS CHAPTER 20 MAINTENANCE STRATEGIES Maintenance and Inspection Options Breakdown or Corrective Maintenance Time-Based or Preventative Maintenance Condition-Based or Predictive Maintenance Inspections Maintenance Strategies for Various Machine Types and Applications Turbogenerators Salient Pole Generators and Motors Squirrel Cage and Wound-Rotor Induction Motors 521 Reference 525 APPENDIXA INSULATION MATERIAL TABLES 527 APPENDIX B INSULATION SYSTEM TABLES 553 INDEX 629