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  • 1. POWER ENGINEERING Series Editor H. Lee Willis Quanta Technology Raleigh, North Carolina Advisory Editor Muhammad H. Rashid University of West Florida Pensacola, Florida 1. Power Distribution Planning Reference Book, H. Lee Willis 2. Transmission Network Protection: Theory and Practice, Y. G. Paithankar 3. Electrical Insulation in Power Systems, N. H. Malik, A. A. Al-Arainy, and M. I. Qureshi 4. Electrical Power Equipment Maintenance and Testing, Paul Gill 5. Protective Relaying: Principles and Applications, Second Edition, J. Lewis Blackburn 6. Understanding Electric Utilities and De-Regulation, Lorrin Philipson and H. Lee Willis 7. Electrical Power Cable Engineering, William A. Thue 8. Electric Systems, Dynamics, and Stability with Artificial Intelligence Applications, James A. Momoh and Mohamed E. El-Hawary 9. Insulation Coordination for Power Systems, Andrew R. Hileman 10. Distributed Power Generation: Planning and Evaluation, H. Lee Willis and Walter G. Scott 11. Electric Power System Applications of Optimization, James A. Momoh 12. Aging Power Delivery Infrastructures, H. Lee Willis, Gregory V. Welch, and Randall R. Schrieber 13. Restructured Electrical Power Systems: Operation, Trading, and Volatility, Mohammad Shahidehpour and Muwaffaq Alomoush 14. Electric Power Distribution Reliability, Richard E. Brown 15. Computer-Aided Power System Analysis, Ramasamy NatarajanDK4058_C000.indd i 11/20/2008 10:17:56 AM
  • 2. 16. Power System Analysis: Short-Circuit Load Flow and Harmonics, J. C. Das 17. Power Transformers: Principles and Applications, John J. Winders, Jr. 18. Spatial Electric Load Forecasting: Second Edition, Revised and Expanded, H. Lee Willis 19. Dielectrics in Electric Fields, Gorur G. Raju 20. Protection Devices and Systems for High-Voltage Applications, Vladimir Gurevich 21. Electrical Power Cable Engineering, Second Edition, William Thue 22. Vehicular Electric Power Systems: Land, Sea, Air, and Space Vehicles, Ali Emadi, Mehrdad Ehsani, and John Miller 23. Power Distribution Planning Reference Book, Second Edition, H. Lee Willis 24. Power System State Estimation: Theory and Implementation, Ali Abur 25. Transformer Engineering: Design and Practice, S.V. Kulkarni and S. A. Khaparde 26. Power System Capacitors, Ramasamy Natarajan 27. Understanding Electric Utilities and De-regulation: Second Edition, Lorrin Philipson and H. Lee Willis 28. Control and Automation of Electric Power Distribution Systems, James Northcote-Green and Robert G. Wilson 29. Protective Relaying for Power Generation Systems, Donald Reimert 30. Protective Relaying: Principles and Applications, Third Edition, J. Lewis Blackburn and Thomas J. Domin 31. Electric Power Distribution Reliability, Second Edition, Richard E. Brown 32. Electrical Power Equipment Maintenance and Testing, Second Edition, Paul GillDK4058_C000.indd ii 11/20/2008 10:17:57 AM
  • 3. ELECTRICAL POWER EQUIPMENT MAINTENANCE AND TESTING SECOND EDITION Paul Gill Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa businessDK4058_C000.indd iii 11/20/2008 10:17:57 AM
  • 4. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2009 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number-13: 978-1-57444-656-2 (Hardcover) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the valid- ity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or uti- lized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopy- ing, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http:// www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For orga- nizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Gill, Paul, 1942- Electrical power equipment maintenance and testing / Paul Gill. -- 2nd ed. p. cm. ISBN 978-1-57444-656-2 (alk. paper) 1. Electric power systems--Testing. 2. Electric power systems--Maintenance and repair. I. Title. TK401.G55 2008 621.31’0420287--dc22 2008029371 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.comDK4058_C000.indd iv 11/20/2008 10:17:57 AM
  • 5. Liability This textbook and instructions offered in it are designed to acquaint students and readers with accepted good practice for maintenance, operation, and testing of electrical equipment and/or systems. This book does not purport to be complete nor is it intended to be specific for the products of any manu- facturer, testing procedures, or maintenance routines. The publisher, the author, companies, and other organizations referenced in this book will not accept any responsibility and liability whatsoever for work undertaken on the basis of this text. The sole purpose of this book is to impart knowledge on the subjects covered in the book. All work undertaken based on this text is the sole responsibility of the reader and user of the book. The manufac- turer’s operating, maintenance, and testing procedures are the only reliable guide in any specific instance and, therefore, they should be consulted before undertaking any work on electrical equipment. The contents of this book do not represent a U.S. Nuclear Regulatory Commission (USNRC) position on the subjects covered in the book. vDK4058_C000.indd v 11/20/2008 10:17:57 AM
  • 6. DK4058_C000.indd vi 11/20/2008 10:17:57 AM
  • 7. Dedication In memory of my parents—Jasbir Singh and Amar Kaur To my wife Patricia—for her patience and understanding to make this work possible To my children/spouses—Shaun/Debra, Rajan/Larie, Jason/Deanna, and Rania/Alden and to my beautiful grandchildren Collin, Andrew, Ryan, Timothy, Owen, Henry, Jack, Maya, Chani, Paul, and Lauryn who keep me young and bring boundless joy to my journey in lifeDK4058_C000.indd vii 11/20/2008 10:17:57 AM
  • 8. DK4058_C000.indd viii 11/20/2008 10:17:57 AM
  • 9. Contents Series Introduction ..................................................................................xxix Foreword .................................................................................................xxxi Preface .................................................................................................. xxxiii Acknowledgments .............................................................................. xxxvii Chapter 1 Maintenance Strategies, Dielectric Theory, Insulating Materials, Failure Modes, and Maintenance Impact on Arc-Flash Hazards 1.1 Introduction ...........................................................................................1 1.2 Why Maintain and Test .......................................................................1 1.3 Overview of Electrical Maintenance and Testing Strategies .........2 1.3.1 Key Factors in EPM Optimization Decisions ...................... 12 1.3.2 General Criteria for an Effective EPM and Testing Program............................................................... 12 1.3.3 Qualifications of EPM Personnel .......................................... 13 1.3.4 Optimization of PM Intervals ............................................... 14 1.3.5 Trending of Test Results......................................................... 15 1.3.6 Systematic Failure Analysis Approach ................................ 15 1.3.6.1 Postmaintenance Testing ......................................... 16 1.3.6.2 Engineering Support ................................................ 16 1.3.6.3 Summary.................................................................... 17 1.4 Planning an EPM Program ............................................................... 18 1.4.1 Maintenance Management Considerations......................... 18 1.4.1.1 Responsibilities .......................................................... 19 1.4.1.2 Inspection ................................................................... 19 1.4.1.3 Scheduling.................................................................. 19 1.4.1.4 Work Orders ............................................................... 20 1.4.1.5 Record Keeping ......................................................... 20 1.4.2 Technical Requirements ......................................................... 20 1.4.2.1 Survey of Plant Equipment ...................................... 20 1.4.2.2 Listing of Plant Equipment in the Order of Critical Importance .............................................. 23 1.4.2.3 Plan to Perform EPM on Regular Frequency........ 24 1.4.2.4 Development of Instruction and Procedures for the EPM Program................................................ 24 1.4.3 What Should Be Included in the EPM Program ................. 25 1.4.3.1 EPM and Testing ....................................................... 25 1.4.3.2 Electrical Repairs ...................................................... 25 1.4.3.3 Analysis of Failures .................................................. 25 1.4.3.4 Trending of Maintenance and Testing Data......... 26 1.4.3.5 Computerized Maintenance Management System ................................................ 26 ixDK4058_C000.indd ix 11/20/2008 10:17:57 AM
  • 10. x Contents 1.5 Overview of Testing and Test Methods .......................................... 28 1.5.1 Types of Tests ........................................................................... 28 1.5.1.1 Acceptance Tests ........................................................ 28 1.5.1.2 Routine Maintenance Tests ...................................... 28 1.5.1.3 Special Maintenance Tests ....................................... 29 1.5.2 Types of Testing Methods ...................................................... 29 1.5.2.1 Solid Insulation Testing ........................................... 29 1.5.2.2 Insulating Liquid Testing ........................................ 30 1.5.2.3 Protective Device Testing ........................................30 1.5.2.4 Circuit Breaker Time–Travel Analysis ................... 31 1.5.2.5 Grounding Electrode Resistance Testing ..................................................... 31 1.5.2.6 Fault Gas Analysis Testing ...................................... 31 1.5.2.7 Infrared Inspection Testing ..................................... 32 1.6 Review of Dielectric Theory and Practice ....................................... 32 1.6.1 Characteristics of Dielectrics (Insulation) ...........................34 1.6.1.1 Dielectric Loss ............................................................ 35 1.6.1.2 PF and DF ................................................................... 35 1.6.1.3 Capacitance ................................................................ 35 1.6.2 Insulation as a Capacitor........................................................ 36 1.6.3 DC Voltage versus AC Voltage Tests .................................... 37 1.6.3.1 DC Voltage Tests........................................................ 38 1.6.3.2 AC Voltage Tests ........................................................ 38 1.6.4 Insulation Breakdown Modes ............................................... 39 1.7 Insulating Materials for Electrical Power Equipment ................................................................................ 40 1.7.1 Rigid Laminates Sheet, Rod, and Tube................................. 41 1.7.2 Glass Polyester Products ........................................................ 41 1.7.3 Flexible Laminates and Films ................................................ 41 1.7.4 Insulation Temperature Ratings ............................................ 46 1.8 Causes of Insulation Degradation and Failure Modes of Electrical Equipment ..................................................................... 47 1.8.1 Failure Modes—Electrical Power Equipment ..................... 51 1.8.1.1 Transformers .............................................................. 51 1.8.1.2 Switchgear and Circuit Breakers ............................ 56 1.8.1.3 Relays ..........................................................................64 1.8.1.4 Switchgear Buses .......................................................65 1.8.1.5 Cables and Connectors ............................................. 69 1.8.1.6 Rotating Machines .................................................... 71 1.9 Maintenance of Protective Devices and their Impact on Arc-Flash Hazard Analysis ......................................................... 81 1.9.1 Bases of Maintenance and Testing of Protective Devices ............................................................... 81 1.9.2 Failure Statistics ....................................................................... 91 1.9.3 Flash Hazard Analysis ........................................................... 92DK4058_C000.indd x 11/20/2008 10:17:57 AM
  • 11. Contents xi Chapter 2 Direct-Current Voltage Testing of Electrical Equipment 2.1 Introduction ......................................................................................... 97 2.2 DC Voltage Testing of Insulation ..................................................... 98 2.2.1 Dielectric Phenomena and Polarization ............................ 100 2.2.2 Advantages and Disadvantages of DC Voltage Testing ...................................................................... 101 2.2.2.1 Advantages.............................................................. 101 2.2.2.2 Disadvantages ........................................................ 102 2.3 DC Testing Methods ........................................................................ 102 2.3.1 Insulation Resistance Testing .............................................. 102 2.3.1.1 Short-Time Readings .............................................. 103 2.3.1.2 Time–Resistance Readings .................................... 103 2.3.1.3 PI Test ....................................................................... 105 2.3.1.4 Step-Voltage Readings (DC Voltage Tip-Up Test) ....................................... 105 2.3.2 High-Potential Voltage Test ................................................. 105 2.4 Transformers ..................................................................................... 106 2.4.1 Insulation Resistance Measurement .................................. 106 2.4.2 Dielectric Absorption Test ................................................... 110 2.4.3 DC High-Potential Test ........................................................ 111 2.5 Cables and Accessories .................................................................... 113 2.5.1 Insulation Resistance Measurement Test .......................... 113 2.5.2 DC Overpotential Testing.................................................... 117 2.5.3 Voltage versus Leakage Current Test (Step-Voltage Test).................................................................. 119 2.5.4 Leakage Current versus Time Test ..................................... 121 2.5.5 Go, No-Go Overpotential Test ............................................ 121 2.5.6 DC Overpotential Test Connections and Procedures ..... 121 2.6 Electrical Switchgear and Circuit Breakers .................................. 124 2.6.1 Insulation Resistance Measurement Test .......................... 124 2.6.2 DC High-Potential Test ........................................................ 126 2.6.3 Circuit Breaker Contact Resistance Measurement Test... 127 2.7 Motors and Generators .................................................................... 127 2.7.1 Insulation Resistance Test .................................................... 128 2.7.1.1 Field-Winding Test Procedures ............................. 128 2.7.1.2 Overall Stator (Armature Windings) Test ........... 129 2.7.1.3 Overall System Test for the Motor or Generator................................................. 130 2.7.1.4 Individual Stator Winding Test............................. 130 2.7.2 DC Overpotential Test .......................................................... 133 2.7.3 Voltage versus Leakage Current Test (Step-Voltage Test).................................................................. 133 2.7.4 Leakage Current versus Time Test ..................................... 134 2.8 Lightning Arresters .......................................................................... 136DK4058_C000.indd xi 11/20/2008 10:17:57 AM
  • 12. xii Contents 2.9 Capacitors ........................................................................................ 137 2.9.1 Tests to Check the Condition of New Capacitor Units before Placing in Service ....................................... 137 2.9.2 Tests to Check the Condition of a Capacitor Unit after It Has Been in Service ............................................. 137 2.10 Evaluation of Test Data Readings ................................................. 139 2.10.1 Acceptance Criteria for Rating Insulation ..................... 140 2.11 Precautions When Making DC Tests ........................................... 143 Chapter 3 Power Factor and Dissipation Factor Testing Methods 3.1 Introduction ..................................................................................... 145 3.2 PF and DF Test Methods................................................................ 146 3.2.1 General ................................................................................ 146 3.2.2 Principles of PF/DF Testing ............................................. 147 3.2.3 Factors That Influence PF Measurements ...................... 148 3.3 Description of the PF Test Equipment ......................................... 149 3.3.1 PF and DF Test Set ............................................................. 149 3.3.2 General Instructions for the Operation of the Megger Test Set ....................................................... 152 3.3.3 Doble PF Test Set ............................................................... 153 3.3.4 Operation of Doble PF Test Set ........................................ 153 3.4 Basic Test Connections (Test Modes) for PF Testing .................. 154 3.4.1 Grounded-Specimen Test Mode ...................................... 154 3.4.2 GST Mode with Guard (GST-G) ...................................... 154 3.4.3 Ungrounded-Specimen Test Mode ................................. 155 3.5 Safety Cautions with PF Testing .................................................. 155 3.6 PF Testing of Electrical Apparatus Insulation ............................ 157 3.6.1 Transformers ...................................................................... 158 3.6.1.1 Two-Winding Transformers .............................. 158 3.6.1.2 Three-Winding Transformers ........................... 161 3.6.1.3 Autotransformers................................................ 163 3.6.1.4 PTs ......................................................................... 163 3.6.2 Transformer Bushing ........................................................ 164 3.6.2.1 Hot-Collar Tests of Noncondenser-Type Bushings ............................................................... 167 3.6.3 Transformer Excitation Current Test .............................. 168 3.6.4 Transformer Insulating Oils and Fluids ........................ 170 3.6.5 Lightning Arrestors .......................................................... 171 3.6.6 Circuit Breakers ................................................................. 171 3.6.6.1 Medium-Voltage Circuit Breakers .................... 172 3.6.6.2 Oil Circuit Breakers (OCBs)............................... 173 3.6.7 SF6 Breaker .......................................................................... 177 3.6.8 Rotating Machinery .......................................................... 177 3.6.8.1 PF Tip-Up Test ..................................................... 178 3.6.9 Cables and Accessories ..................................................... 180 3.6.9.1 Shielded or Sheathed Cable ............................... 181 3.6.9.2 Unshielded and Unsheathed Cables ................ 181DK4058_C000.indd xii 11/20/2008 10:17:57 AM
  • 13. Contents xiii 3.6.10 PF Correction Capacitors and Surge Capacitors ............. 182 3.6.10.1 Bus Insulators....................................................... 183 3.6.10.2 Miscellaneous Equipment.................................. 183 3.7 Evaluation and Grading of PF and DF Test Results .......................................................................... 184 3.7.1 General .................................................................................. 184 3.7.2 Analysis of the Results ....................................................... 185 3.7.2.1 Transformers ........................................................ 185 3.7.2.2 Bushings ............................................................... 187 3.7.2.3 Lightning and Surge Arrestors ......................... 188 3.7.2.4 Medium-Voltage Circuit Breakers..................... 188 3.7.2.5 OCB ....................................................................... 189 3.7.2.6 SF6 Breakers .......................................................... 189 3.7.2.7 Rotating Machines .............................................. 190 3.7.2.8 Cables and Accessories....................................... 190 3.7.2.9 Capacitors ............................................................. 190 Chapter 4 Insulating Oils, Fluids, and Gases 4.1 Introduction ....................................................................................... 193 4.2 Insulating Oil .................................................................................... 193 4.2.1 Deterioration of Insulating Oil .......................................... 194 4.2.1.1 Effect of Oxygen on Oil ...................................... 194 4.2.1.2 Moisture in Oil .................................................... 194 4.2.1.3 Oil Deterioration in Transformers .................... 195 4.2.1.4 Absorption of Moisture by Insulating Materials ........................................... 196 4.2.1.5 Absorption of Nitrogen by Oil .......................... 196 4.2.2 Insulating Oil Testing ......................................................... 196 4.2.2.1 Dielectric Breakdown Voltage Test (Cup Tests) ...................................... 197 4.2.2.2 Acidity Test ........................................................... 200 4.2.2.3 Interfacial Tension (IFT) ..................................... 201 4.2.2.4 Color Test .............................................................. 201 4.2.2.5 Power Factor Test ................................................. 201 4.2.2.6 Specific Gravity .................................................... 202 4.2.2.7 Water Content Test (Karl Fisher Method) ........ 202 4.2.3 Combustible Gas Analysis of Insulating Oil ................... 203 4.2.3.1 Introduction .......................................................... 203 4.2.3.2 TCG ........................................................................ 203 4.2.3.3 DGA ....................................................................... 204 4.2.3.4 Comparing the Two Methods ............................ 204 4.2.3.5 Interpretation of Gas Analysis........................... 204 4.2.3.6 Assessing the Transformer Condition Using the TCGA in the Gas Space .................... 206 4.2.3.7 Assessing the Transformer Condition Using the DGA Method...................................... 207 4.2.3.8 Fault Types and Associated Key Gases ............ 208DK4058_C000.indd xiii 11/20/2008 10:17:57 AM
  • 14. xiv Contents 4.3 Less Flammable Insulating Fluids ................................................. 209 4.4 Insulating Liquid Sampling Procedures ....................................... 210 4.4.1 Sampling Oil from Transformers........................................ 211 4.4.2 Sampling Oil from Drums or Shipping Containers ........................................................ 211 4.4.3 Taking Oil Samples for Gas-in-Oil Analysis .................... 212 4.5 Maintenance and Reconditioning of Insulating Oil and Fluids .................................................................................... 212 4.5.1 Reconditioning Used Insulating Oils ................................ 213 4.5.1.1 Natural Precipitation .............................................. 213 4.5.1.2 Filter Presses............................................................ 214 4.5.1.3 Filter Press Operation ............................................ 215 4.5.1.4 Cartridge Filters ...................................................... 215 4.5.1.5 Centrifuges .............................................................. 215 4.5.1.6 Coalescers ................................................................ 217 4.5.1.7 Vacuum Dehydrators ............................................. 217 4.5.2 Maintenance of Less Flammable Fluids ............................ 217 4.5.2.1 Maintenance of RTemp .......................................... 217 4.5.2.2 Maintenance of Silicone ........................................ 218 4.5.2.3 Maintenance of Wecosol ....................................... 220 4.5.2.4 Maintenance of Environtemp (FR3) .................... 223 4.5.2.5 Maintenance of Askarels ...................................... 227 4.6 Insulating Gases ............................................................................... 231 4.6.1 Maintenance of SF6................................................................ 231 4.6.1.1 Conducting Particles .............................................. 231 4.6.1.2 Moisture ................................................................... 232 4.6.1.3 Oil Contamination.................................................. 232 4.6.1.4 Gaseous Contamination ........................................ 233 4.6.1.5 Arc Products ............................................................ 233 Chapter 5 Transformers 5.1 Introduction ....................................................................................... 235 5.2 Transformer Categories and Type .................................................. 235 5.2.1 Insulating Medium ............................................................... 235 5.2.1.1 Dry Type .................................................................. 236 5.2.1.2 Liquid-Filled Transformer ..................................... 236 5.2.2 Construction .......................................................................... 237 5.2.2.1 Tank Construction.................................................. 237 5.2.2.2 Core Construction .................................................. 238 5.3 Application and Use ......................................................................... 238 5.3.1 Distribution Transformers ................................................... 238 5.3.2 Network Transformer........................................................... 239 5.3.3 Arc-Furnace Transformer .................................................... 239 5.3.4 Rectifier Transformer............................................................ 240 5.3.5 Power Transformer ............................................................... 240 5.4 Transformer Fundamentals............................................................. 240DK4058_C000.indd xiv 11/20/2008 10:17:57 AM
  • 15. Contents xv 5.4.1 Voltage Relationship ............................................................. 244 5.4.2 Current Relationship ............................................................ 244 5.4.3 Impedance Relationship ...................................................... 244 5.4.4 Summary................................................................................ 245 5.5 Transformer Polarity, Terminal Markings, and Connections ............................................................................... 246 5.5.1 Single-Phase Transformers .................................................. 246 5.5.1.1 Subtractive Polarity ................................................. 246 5.5.1.2 Additive Polarity ..................................................... 247 5.5.2 Three-Phase Transformers .................................................. 247 5.6 Transformer Characteristics ............................................................ 250 5.7 Preventive Maintenance of Transformers ..................................... 253 5.7.1 Transformer Installation, Acceptance, and Maintenance ..................................................................254 5.7.1.1 Unscheduled Maintenance ....................................254 5.7.1.2 Ordinary Maintenance ...........................................254 5.7.1.3 Protective Maintenance ..........................................254 5.7.2 Dry-Type Transformers ........................................................ 255 5.7.2.1 Installation ............................................................... 255 5.7.2.2 Inspection ................................................................. 257 5.7.2.3 Acceptance Tests...................................................... 258 5.7.2.4 Maintenance............................................................. 260 5.7.2.5 Drying-Out Methods .............................................. 261 5.7.2.6 Storage....................................................................... 263 5.7.3 Liquid-Type Transformer ..................................................... 263 5.7.3.1 Installation ............................................................... 263 5.7.3.2 Inspection ................................................................. 265 5.7.3.3 Acceptance Tests...................................................... 265 5.7.3.4 Maintenance............................................................. 267 5.7.3.5 Drying-Out Methods .............................................. 271 5.7.3.6 Storage....................................................................... 273 5.7.3.7 Transformer Diagnostic Guide .............................. 273 5.8 Transformer Testing ......................................................................... 275 5.8.1 AC Hi-Pot Test ....................................................................... 276 5.8.2 TTR Test.................................................................................. 276 5.8.2.1 Alternative Test for TTR ......................................... 279 5.8.2.2 TTR Capacitor .......................................................... 280 5.8.3 Polarity Test ........................................................................... 281 5.8.4 Induced Potential Test .......................................................... 281 5.8.5 FRA ......................................................................................... 282 5.8.6 DC Winding Resistance ....................................................... 285 5.8.7 Transformer Core Ground Test ........................................... 286 5.8.8 Polarization Recovery Voltage Test .................................... 286 5.8.8.1 The Measuring Instrument.................................... 287 5.8.8.2 Test Setup for Recovery Voltage Measurement on Power Transformers .......................................... 288DK4058_C000.indd xv 11/20/2008 10:17:57 AM
  • 16. xvi Contents 5.8.8.3 Evaluation of Measured Polarization Spectra .......................................... 290 5.9 Online Condition Monitoring of Transformers.......................... 291 5.9.1 Online Monitoring of Transformers ............................... 292 5.10 Online Monitoring of Bushings and Lightning Arrestors........ 296 Chapter 6 Cables and Accessories 6.1 Introduction ..................................................................................... 299 6.2 Cable Construction and Classification......................................... 299 6.2.1 Types of Conductors ..........................................................300 6.2.2 Conductor Arrangement ................................................... 301 6.2.3 Cable Types ......................................................................... 301 6.2.4 Insulations........................................................................... 302 6.2.5 Shielding and Semiconducting Tape...............................305 6.2.6 Finishes and Jackets ...........................................................306 6.2.7 Cable Construction ............................................................ 307 6.3 Cable Characteristics ......................................................................308 6.4 Electrical Constants ........................................................................ 312 6.5 Cable Ratings ................................................................................... 314 6.6 Cable Selection and Application ................................................... 317 6.7 Installation of Cables ...................................................................... 322 6.7.1 Outdoor Installations ........................................................ 322 6.7.2 Indoor Installations ........................................................... 323 6.7.3 Bending Data ...................................................................... 323 6.7.4 Pulling Tensions................................................................. 323 6.8 Maintenance of Cables ................................................................... 325 6.9 Cable Failures and Their Analysis ............................................... 326 6.10 Field Testing of Medium-Voltage Cables ..................................... 330 6.10.1 Cable Degradation and Diagnostic Tests ....................... 330 6.10.2 Safety Practices and Grounding ......................................334 6.10.3 Cable Testing Methods ..................................................... 335 6.10.3.1 Insulation Resistance and DC Hi-Pot Testing..................................................... 335 6.10.3.2 AC Hi-Pot Testing .............................................. 336 6.10.3.3 PF and DF Testing ............................................. 337 6.10.3.4 VLF Tests............................................................. 338 6.10.3.5 PD Test ................................................................ 341 6.10.3.6 AC Resonance Test ............................................346 6.10.3.7 Summary of Testing Methods .........................348 6.11 Latest Trends in Cable Condition Monitoring and Aging Assessment................................................................... 352 6.11.1 Electronic Characterization and Diagnostic (ECAD® ) System ............................................ 352 6.11.2 Cable Indentor .................................................................... 352 6.11.3 Oscillating Wave (OSW) Testing ..................................... 353DK4058_C000.indd xvi 11/20/2008 10:17:58 AM
  • 17. Contents xvii 6.11.4 Broadband Impedance Spectroscopy Prognostic/Diagnostic Technique ..................................354 6.12 Cable Fault Locating Methods ...................................................... 356 6.12.1 Terminal Techniques ........................................................ 356 6.12.2 Tracer Techniques ............................................................. 362 6.12.3 Application Guide for Cable Fault Locating ................. 367 Chapter 7 Medium-Voltage Switchgear and Circuit Breakers 7.1 General.............................................................................................. 377 7.2 Medium-Voltage Switchgear ......................................................... 377 7.2.1 Construction Features ...................................................... 377 7.2.1.1 Metal-Clad Switchgear ....................................... 378 7.2.1.2 Metal-Enclosed Interrupter Switchgear ........... 382 7.2.1.3 Station-Type Cubicle ........................................... 382 7.2.2 Short-Circuit Considerations and Power Circuit Breaker Ratings .................................................................. 383 7.2.3 Selection and Application of Power Circuit Breakers ................................................................. 392 7.3 Electrical Switchgear Maintenance and Care ............................. 393 7.3.1 MV Switchgear................................................................... 393 7.3.1.1 Power Circuit Breakers ....................................... 393 7.3.1.2 Maintenance ........................................................ 395 7.3.2 Air-Magnetic Circuit Breakers ........................................ 396 7.3.3 Oil Circuit Breaker ............................................................ 398 7.3.4 Vacuum Circuit Breaker ................................................... 399 7.3.5 Switchgear Enclosure and Bus ........................................400 7.4 Electrical Switchgear Testing ........................................................ 403 7.4.1 Insulation Resistance Measurement Test ....................... 403 7.4.2 DC Hi-Pot Test ...................................................................405 7.4.3 AC Hi-Pot Test....................................................................405 7.4.4 Power Factor Testing ......................................................... 407 7.4.5 Circuit Breaker Contact Resistance Measurement Test.............................................................. 407 7.4.6 Circuit Breaker Time–Travel Analysis............................ 407 7.4.7 Dynamic Capacitance Measurement of HV Breaker ... 413 7.5 Control Power for Switchgear ....................................................... 415 7.5.1 Control Power Requirements........................................... 415 7.5.1.1 Circuit Breaker Tripping .................................... 416 7.5.1.2 DC Battery Trip ................................................... 416 7.5.1.3 Capacitor Trip ...................................................... 416 7.5.1.4 AC Methods of Tripping .................................... 418 7.5.1.5 Circuit Breaker Closing ...................................... 418 7.6 DC (Battery) Control Power Equipment ...................................... 420 7.6.1 Sizing .................................................................................... 420DK4058_C000.indd xvii 11/20/2008 10:17:58 AM
  • 18. xviii Contents 7.6.2 Types of Batteries .................................................................. 421 7.6.3 Battery Chargers ...................................................................422 7.7 AC Control Power Equipment.........................................................422 7.7.1 Sizing ......................................................................................422 7.7.2 Application ............................................................................423 7.8 Maintenance and Care of Batteries for Switchgear Applications ............................................................423 7.8.1 Inspections.............................................................................423 7.8.2 Equalizing Charge ................................................................ 424 7.8.3 Battery Tests...........................................................................425 7.8.3.1 Acceptance Test ......................................................425 7.8.3.2 Performance Test ....................................................425 7.8.3.3 Battery Service Test (Load Test)............................ 426 7.8.3.4 Connection Resistance Test ................................... 427 7.8.3.5 Battery Impedance Test ......................................... 427 7.8.4 Addition of Water ................................................................. 427 7.8.5 Acid Spillage.......................................................................... 428 7.8.6 Loose Connections ............................................................... 429 7.8.7 Corrosion ............................................................................... 429 7.8.9 Other Maintenance Hints .................................................... 429 Chapter 8 Low-Voltage Switchgear and Circuit Breakers 8.1 Low-Voltage Switchgear................................................................... 431 8.2 Low-Voltage Circuit Breakers ......................................................... 432 8.2.1 MCCBs....................................................................................433 8.2.2 Insulated-Case Circuit Breakers .........................................433 8.2.3 Power Circuit Breakers ........................................................433 8.2.4 Fused Power Circuit Breakers.............................................434 8.3 Overcurrent Protective Devices .....................................................434 8.3.1 Direct-Acting Trip.................................................................434 8.3.2 Static- and Electronic-Trip Units ......................................... 435 8.3.3 Monitoring and Protection Packages................................. 439 8.4 Fuses ................................................................................................... 439 8.4.1 Low-Voltage Fuses ................................................................440 8.5 Disconnect Switches......................................................................... 441 8.5.1 Low-Voltage Switches........................................................... 441 8.6 Selection and Application of Low-Voltage Equipment ...............442 8.6.1 Assessing Service Life of Low-Voltage Breakers ..............444 8.6.1.1 Maximum Voltage Rating or Nominal Voltage Class ...........................................................444 8.6.1.2 Continuous Current Rating ..................................444 8.6.1.3 Rated Short-Circuit Current (Circuit Breakers) ....................................................445 8.6.1.4 Short-Circuit Current Ratings—Panelboards, MCCs, and Switchgear Assemblies ..................... 447 8.6.1.5 Endurance Requirements for Low-Voltage Breakers ......................................448DK4058_C000.indd xviii 11/20/2008 10:17:58 AM
  • 19. Contents xix 8.7 Low-Voltage Switchgear Maintenance and Care........................ 450 8.7.1 General Guidelines for Inspection and Maintenance of Switchgear .............................................. 450 8.7.2 Maintenance of Power Circuit Breakers .........................454 8.7.2.1 Mechanical Maintenance Factors ................... 456 8.7.2.2 Electrical Maintenance Factors........................ 458 8.7.2.3 Inspections Procedure ...................................... 459 8.7.3 MCCBs ................................................................................. 460 8.7.3.1 Mechanical Factors............................................ 460 8.7.3.2 Electrical Factors................................................ 462 8.7.3.3 Inspections Procedure ......................................463 8.7.4 Switchgear Enclosure ........................................................ 463 8.7.5 Air Disconnect Switches, Fuses, and Insulators .....................................................................463 8.7.5.1 Air Disconnect Switches ..................................464 8.7.5.2 Power Fuses........................................................464 8.7.5.3 Insulators ............................................................ 465 8.8 Maintenance and Testing of Low-Voltage Protective Devices ........................................................................... 465 8.8.1 Power Circuit Breaker Overcurrent Trip Devices ........................................................................ 466 8.8.1.1 Overcurrent Trip Units ..................................... 466 8.8.2 Molded-Case Breaker Trips .............................................. 470 8.8.2.1 Protective Trip Testing...................................... 471 8.8.2.2 Verification Testing ........................................... 472 8.8.3 Overload Relays ................................................................. 474 8.8.4 Testing of Ground Fault Sensing and Relaying Equipment ........................................................................... 474 8.8.4.1 Preparation for Fielding Training ................... 475 8.8.4.2 Field Testing ....................................................... 475 8.9 Uninterruptible Power Supply Commissioning and Testing ....................................................................................... 477 8.9.1 Background ......................................................................... 477 8.9.2 Preinstallation Checks and Tests ..................................... 478 8.9.3 Combined Test (UPS with the Generator) ......................480 8.9.4 Maintenance Test ...............................................................480 8.9.4.1 UPS Battery System...........................................480 8.9.5 Maintenance and Testing.................................................. 486 8.9.6 Summary ............................................................................. 486 8.10 Infrared Inspection of Electrical Equipment .............................. 487 8.10.1 Types of Thermographic Scanners .................................. 487 8.10.2 Conducting an IR Thermographic Inspection .............. 488 8.10.2.1 Delta-T Temperature Rating Systems ............. 488 8.10.2.2 Standards-Based Temperature Rating System .................................................... 490 8.10.3 Conducting a Thermographic Survey ............................ 493 8.10.4 Examples of Thermographic Findings ............................ 494DK4058_C000.indd xix 11/20/2008 10:17:58 AM
  • 20. xx Contents Chapter 9 Testing and Commissioning of Protective Relays and Instrument Transformers 9.1 Introduction ....................................................................................... 497 9.2 Instrument Transformers ................................................................ 497 9.2.1 Current Transformers ........................................................... 498 9.2.1.1 CT Accuracy Standards ......................................... 499 9.2.1.2 Accuracy Classes for Metering .............................500 9.2.1.3 Accuracy Classes for Relaying ..............................500 9.2.2 Voltage (Potential) Transformers ......................................... 501 9.2.3 Polarity of Instrument Transformers.................................. 502 9.2.3.1 Testing for Polarity of Instrument Transformers ............................................................ 503 9.2.4 Testing for Ratio of Instrument Transformers ..................504 9.2.5 Winding and Lead Resistance Measurements .................. 507 9.2.6 Burden Measurements.......................................................... 507 9.2.7 CT Remanence ....................................................................... 507 9.2.8 Grounding of CT ...................................................................508 9.2.9 Maintenance and Testing of Instrument Transformers .......................................................................... 509 9.3 Protective Relays ............................................................................... 510 9.3.1 Classification of Relays ......................................................... 510 9.3.2 Overview of Protective Relays—Construction and Types................................................................................ 510 9.3.2.1 Electromechanical and Induction Relays (First-Generation Relays) ........................................ 511 9.3.2.2 Static Relays (Second-Generation Relays) ............ 512 9.3.2.3 Solid-Sate Relays (Third-Generation Relays) ...... 513 9.3.2.4 Microprocessor Relays (Fourth-Generation Relays) ....................................................................... 513 9.4 Relay Application and Principles ................................................... 515 9.5 Types of Relay Tests.......................................................................... 519 9.6 Testing and Maintenance of Electromechanical Protective Relays ............................................................................... 521 9.6.1 Relay Inspection and Tests................................................... 521 9.6.2 Protective Relay Test Procedures and Circuits ............................................................................ 524 9.6.3 Relay Test Points and Test Circuits ..................................... 524 9.6.4 Instrument Transformers Calibration ................................ 527 9.7 Testing and Commissioning of Static and Digital Relays ............................................................................ 531 9.7.1 Test Methods .......................................................................... 533 9.7.2 Commissioning Methods .....................................................534 9.7.3 Commissioning Examples ................................................... 536 9.8 Event Reporting ................................................................................540DK4058_C000.indd xx 11/20/2008 10:17:58 AM
  • 21. Contents xxi Chapter 10 Motors and Generators 10.1 General ............................................................................................. 549 10.2 NEMA Classification of Motors and Generators ....................... 549 10.2.1 According to Size............................................................... 550 10.2.2 According to Application ................................................. 550 10.2.3 According to Electrical Type............................................ 551 10.2.3.1 AC Motors .......................................................... 551 10.2.3.2 Polyphase Motor................................................ 551 10.2.3.3 Single-Phase Motor ........................................... 552 10.2.3.4 Universal Motor................................................. 553 10.2.3.5 DC Motors .......................................................... 553 10.2.3.6 DC Generators ................................................... 554 10.2.4 According to Physical Protection (Enclosure) and Methods of Cooling ................................................... 554 10.2.5 According to Variability of Speed ................................... 555 10.2.6 Terminal Marking of Machines....................................... 556 10.2.6.1 Single-Voltage Motors ....................................... 557 10.2.6.2 Dual-Voltage Motors ......................................... 557 10.2.6.3 Polyphase Motors .............................................. 557 10.3 Applications of Motors and Generators ...................................... 559 10.3.1 Electrical Integrity ............................................................. 560 10.3.1.1 Dielectric Rating ................................................ 560 10.3.1.2 Load–Time Rating ............................................. 561 10.3.2 Mechanical Integrity ......................................................... 562 10.4 AC Motors ........................................................................................ 562 10.4.1 Environmental Conditions ............................................... 562 10.4.2 Direction of Rotation ......................................................... 563 10.4.3 Operation at Altitudes above 3300 ft............................... 563 10.4.4 Voltage and Frequency ..................................................... 563 10.4.5 Horsepower, Torque, and Speed Considerations.......... 565 10.4.6 Power Factor ....................................................................... 567 10.4.7 Motor Selection .................................................................. 567 10.5 AC Generators ................................................................................. 568 10.5.1 Service Conditions............................................................. 568 10.5.2 Ratings ................................................................................ 569 10.5.3 Temperature Rise ............................................................... 569 10.5.4 Variation in Voltage ........................................................... 570 10.5.5 Regulation .......................................................................... 570 10.6 DC Motors ........................................................................................ 570 10.6.1 Service Conditions............................................................. 570 10.6.2 Operation of DC Motor on Rectified AC........................ 570 10.6.3 Operation of the DC Motor below Base Speed ............. 571 10.6.4 Operation of the DC Motor above Base Speed .............. 571 10.6.5 Overload Capability .......................................................... 571DK4058_C000.indd xxi 11/20/2008 10:17:58 AM
  • 22. xxii Contents 10.7 DC Generators ................................................................................. 572 10.7.1 Service Conditions ........................................................... 572 10.7.2 Ratings ............................................................................... 572 10.7.3 Temperature Rise ............................................................. 572 10.7.4 Overload Capability......................................................... 572 10.7.5 Voltage Excitation ............................................................. 572 10.7.6 Overspeed ......................................................................... 572 10.8 Motor and Generator Insulation Systems ................................... 572 10.8.1 Machine Insulation System ............................................ 572 10.9 Motor and Generator Maintenance .............................................. 576 10.9.1 Failure Mechanisms ........................................................ 576 10.9.1.1 Stator-Winding Insulation ............................. 576 10.9.1.2 Rotor-Winding Insulation ............................. 577 10.9.1.3 Exciter Insulation ............................................ 577 10.9.2 General Inspection ........................................................... 577 10.9.2.1 Visual Inspection ............................................ 578 10.9.3 DC Motors and Generators and Repulsion-Induction Motors .......................................... 580 10.9.3.1 Cleanliness ...................................................... 580 10.9.3.2 Armature ......................................................... 581 10.9.3.4 Field Windings ................................................ 587 10.9.4 Induction Motor................................................................ 588 10.9.4.1 Stator Windings .............................................. 589 10.9.4.2 Air Gap............................................................. 589 10.9.4.3 Wound-Rotor Windings ................................ 590 10.9.4.4 Brushes and Rings .......................................... 591 10.9.4.5 Centrifugal Switches ...................................... 591 10.9.4.6 Squirrel-Cage Rotors ...................................... 591 10.9.5 Synchronous Motors and Generators ........................... 592 10.9.6 Cleaning and Varnishing of Machine Windings ...................................................... 593 10.9.6.1 Cleaning ........................................................... 593 10.9.6.2 Drying .............................................................. 594 10.9.6.3 Varnish ............................................................. 595 10.9.7 Lubrication, Bearings, and Oil Seals ............................. 596 10.9.7.1 Lubrication ....................................................... 596 10.9.7.2 Sleeve Bearings ............................................... 596 10.9.7.3 Antifriction Bearings ..................................... 598 10.9.7.4 Installation of Oil Seals.................................. 599 10.9.8 Brushes ..............................................................................600 10.9.8.1 Brush Adjustment........................................... 601 10.9.9 Balancing ........................................................................... 602 10.9.9.1 Need for Balancing......................................... 603 10.9.9.2 Imbalance Measurement ............................... 603 10.9.10 Belts, Gears, and Pinions................................................. 603 10.9.10.1 Belts................................................................... 603 10.9.10.2 Gears and Pinions ..........................................604DK4058_C000.indd xxii 11/20/2008 10:17:58 AM
  • 23. Contents xxiii 10.10 Predictive Maintenance Guide on Motors and Variable Frequency Drives ...................................................604 10.10.1 Power Quality ................................................................. 605 10.10.2 Power Circuit................................................................... 611 10.10.3 Insulation Condition ...................................................... 615 10.10.4 Stator Condition .............................................................. 621 10.10.5 Rotor Condition .............................................................. 625 10.10.6 Air Gap.............................................................................630 10.11 Testing of Motors and Generators ..............................................643 10.11.1 Insulation Resistance and Dielectric Absorption Tests .............................................................650 10.11.2 High-Potential Test .........................................................650 10.11.3 PF Test .............................................................................. 652 10.11.4 Dissipation Factor Tan d Test ........................................ 653 10.11.5 Partial Discharge Test ....................................................654 10.11.6 Slot Discharge Test ......................................................... 657 10.11.7 Conductor Insulation Tests ........................................... 657 10.11.8 Motor and Generator Component Tests ...................... 657 10.11.9 Voltage Surge Comparison Test ................................... 659 10.12 Other Insulation Test Methods ................................................... 660 10.12.1 Very Low Frequency Testing ........................................ 660 10.12.2 Series Resonant Testing ................................................. 662 10.13 Vibration Analysis ........................................................................ 663 Chapter 11 Electrical Power System Grounding and Ground Resistance Measurements 11.1 Introduction ................................................................................... 665 11.2 Selection of Grounding Method ................................................. 666 11.2.1 Ungrounded Systems .................................................... 666 11.2.2 Solidly Grounded Systems ............................................ 668 11.2.3 Reactance and Resistance Grounded Systems ........... 669 11.2.4 Resonant Grounding...................................................... 672 11.2.5 Grounding Ungrounded Systems ................................ 673 11.3 Selection of Grounding System ................................................... 676 11.3.1 Solidly Grounded System.............................................. 677 11.3.2 Low-Resistance Grounding .......................................... 678 11.3.3 High-Resistance Grounding ......................................... 679 11.3.4 Reactance Grounding .................................................... 679 11.3.5 Ground-Fault Neutralizers (Resonant Grounded) .... 679 11.4 Understanding Ground Resistance ............................................680 11.4.1 Grounding Electrode Resistance..................................680 11.4.2 Effect of Ground Electrode Size and Depth on Resistance ................................................................... 682 11.4.3 Effect of Soil Resistivity on Ground Electrode Resistance.......................................................684 11.4.4 Factors Affecting Soil Resistivity .................................684 11.4.5 Effect of Ground Electrode Depth on Resistance ...... 687DK4058_C000.indd xxiii 11/20/2008 10:17:58 AM
  • 24. xxiv Contents 11.5 Ground Resistance Values ............................................................. 687 11.6 Ground Resistance Measurements .............................................. 689 11.6.1 Two-Point Method ............................................................ 689 11.6.2 Three-Point Method ......................................................... 690 11.6.3 Fall-of-Potential Method .................................................. 692 11.6.3.1 Position of the Auxiliary Electrodes on Measurements.............................................. 693 11.6.3.2 Measuring Resistance of Ground Electrodes (62% Method) ................................. 694 11.6.3.3 Auxiliary Electrode Spacing ........................... 696 11.6.3.4 Multiple Electrode System ............................... 697 11.6.4 Ratio Method ..................................................................... 700 11.6.5 Soil Resistivity Measurements (Four-Point Measurement) .................................................................... 701 11.6.6 Touch Potential Measurements ....................................... 702 11.6.7 Clamp-On Ground Resistance Measurement............... 704 11.6.7.1 Principle of Operation ...................................... 704 11.6.7.2 In-Field Measurement ...................................... 705 11.6.7.3 Transmission Towers ........................................ 709 11.6.7.4 Central Office Locations .................................. 710 11.7 Ground Grid Integrity Measurements ........................................ 710 Chapter 12 Power Quality, Harmonics, and Predictive Maintenance 12.1 Background ..................................................................................... 715 12.2 PQ Concept and Fundamentals ................................................... 716 12.2.1 Types and Consequences of Electrical Disturbances .. 717 12.3 Origins of PQ Problems and Harmonics .................................... 726 12.4 Characteristics of Typical Linear and Nonlinear Loads ........... 729 12.4.1 Voltage and Current Characteristics of Nonlinear Loads ........................................................... 731 12.4.1.1 HD Terminology ............................................... 731 12.4.1.2 Types of Nonlinear Loads ............................... 732 12.4.1.3 PF Characteristics of Loads ............................. 735 12.4.1.4 Phase Sequence of Harmonics ........................ 739 12.4.1.5 Harmonic Generating Characteristics ........... 742 12.4.1.6 Sensitivity to Harmonics ................................. 742 12.4.1.7 Sensitivity to Voltage Variation ...................... 743 12.4.1.8 Sensitivity to Voltage Flicker........................... 743 12.4.1.9 Sensitivity to Noise........................................... 743 12.5 Effects of Harmonic on Power System Equipment and Loads ........................................................................................ 743 12.5.1 Basic Concepts on Effects of Harmonics ....................... 744 12.5.1.1 Thermal Stress................................................... 745 12.5.1.2 Insulation Stress ................................................ 747 12.5.1.3 Load Disruption ................................................ 747DK4058_C000.indd xxiv 11/20/2008 10:17:58 AM
  • 25. Contents xxv 12.5.2 Harmonic Effects on Power System Equipment ............................................................ 748 12.5.2.1 Transformers ................................................... 748 12.5.2.2 Rotating Machines ......................................... 751 12.5.2.3 Capacitor Banks .............................................. 753 12.5.2.4 Switchgear ....................................................... 756 12.5.2.5 Protective Relays ............................................ 757 12.5.2.6 Metering Devices............................................ 758 12.5.2.7 Electronic Equipment .................................... 758 12.5.2.8 Lighting Devices............................................. 759 12.6 Predictive Maintenance and PQ Measurements........................ 759 12.6.1 Introduction ....................................................................... 759 12.6.2 Safety Standards for Test Instruments .......................... 760 12.6.2.1 Test Instrument Standards ............................ 760 12.6.2.2 Instruments for PQ Measurements ............. 762 12.6.3 PQ Measurement Guidelines .......................................... 764 12.6.3.1 Preparation for Conducting Measurements ................................................. 764 12.6.3.2 Basic Power Measurements........................... 766 12.6.3.3 Measurements at the Receptacle of a Branch Circuit.......................................... 768 12.6.3.4 Measurement at the Service Panel ............... 774 12.6.3.5 Measurements at the Transformer ............... 778 12.6.3.6 Electrical Noise ............................................... 787 12.6.3.7 Transients......................................................... 791 12.6.3.8 Lightning ......................................................... 794 12.6.3.9 Polyphase Induction Motors ......................... 795 12.6.3.10 PQ Measurements of VFDs ........................... 798 12.6.3.11 Power System Resonance...............................800 12.6.3.12 Commercial Lighting Load ...........................803 12.6.3.13 Summary of PQ Problems .............................804 12.7 PQ Solution and Power Treatment Devices ................................806 12.7.1 Voltage Disturbances and Noise ..................................... 807 12.7.1.1 Noise Filters (Electronic Filters) ...................808 12.7.1.2 TVSS..................................................................808 12.7.1.3 Voltage Regulators ..........................................809 12.7.1.4 Isolation Transformers ................................... 812 12.7.1.5 Power Conditioners ........................................ 812 12.7.1.6 UPS ................................................................... 815 12.7.2 HDs ..................................................................................... 817 12.7.2.1 Industry Standards on Limits of Harmonics ................................................... 818 12.7.2.2 Evaluating System Harmonics ...................... 818 12.7.2.3 Harmonic Solutions—Mitigation Devices and Methods ..................................... 820 12.7.3 Wiring and Grounding Problems .................................. 823DK4058_C000.indd xxv 11/20/2008 10:17:58 AM
  • 26. xxvi Contents Chapter 13 Electrical Safety, Arc-Flash Hazard, Switching Practices, and Precautions 13.1 Introduction..................................................................................... 827 13.2 Industry Standards and Regulatory Requirements for Safety .......................................................................................... 828 13.2.1 ANSI C2: The National Electrical Safety Code-2007.............................................................. 828 13.2.2 ANSI/National Fire Protection Association (NFPA) 70, National Electrical Code (NEC)-2008........ 829 13.2.3 ANSI/NFPA 70B, Standard for Electrical Equipment Maintenance-2006 .......................................830 13.2.4 ANSI/NFPA 70E, Standard for Electrical Safety in the Workplace-2004 .....................................................830 13.2.5 Occupational Safety and Health Administration (OSHA) Standards ........................................................... 837 13.3 Arc-Flash Hazard and Regulatory Requirements ..................... 839 13.3.1 Summary of NFPA 70, 70E, and OSHA Requirements ...................................................................... 841 13.3.2 Overview of Arc-Flash Hazard ..................................... 841 13.3.3 Arc-Flash Analysis ..........................................................842 13.4 Electrical Safety Practices and Precautions ................................844 13.4.1 Electrical Safety ...............................................................844 13.4.2 “On-Site” Electrical Safety..............................................844 13.4.3 “On-Site” Safety Kit .........................................................845 13.4.4 Work Area Control ..........................................................846 13.4.5 Lock-Out and/or Tagging ..............................................848 13.4.6 Protective Apparel-Operating Electrical Equipment ....................................................... 849 13.4.7 Testing of Electrical Circuits and/or Equipment ........................................................... 850 13.4.8 Rubber Gloves for Electrical Work-Use and Care ....... 851 13.4.9 Low-Voltage Tester ..........................................................854 13.4.10 Medium- and HV-Detectors .......................................... 855 13.4.11 Grounds-Personnel Protection ...................................... 857 13.5 Electrical Switching Practices and Precautions ......................... 859 13.5.1 On-Site Circuit Breaker Maintenance Safety Checklists ..............................................................859 13.5.2 Confined Spaces—Procedure for Entering ..................864 13.5.3 Electrical Precautions ...................................................... 869 13.5.3.1 General Precautions ........................................ 869 13.5.3.2 Loads and Currents ........................................ 869 13.5.3.3 Switch Sticks .................................................... 870 13.5.3.4 Opening Disconnects by Using the “Inching” Method .................................... 871 13.5.3.5 Selector Disconnects ....................................... 872 13.5.3.6 Circuit Breaker Disconnects .......................... 872 13.5.3.7 Interrupter Switches ....................................... 873DK4058_C000.indd xxvi 11/20/2008 10:17:58 AM
  • 27. Contents xxvii 13.5.3.8 Closing Disconnects under Load Conditions ............................................ 873 13.5.3.9 Air Break Switches ........................................ 873 13.5.3.10 Protection against Air Break Flashover...... 874 13.5.3.11 Motor-Controlled Disconnects and Air Breaks ............................................... 875 13.6 Electrical Fire Emergencies ........................................................... 875 13.6.1 Never Make Direct Contact with Any Energized Object.............................................................. 875 13.6.2 Stay Clear of Vicinity of Any Faulty Energized Object ............................................................. 876 13.6.3 Be Alert in Vicinity of Any Energized Object ............ 876 13.6.3.1 Beware of Covered Wires ............................. 877 13.6.3.2 Beware of Telephone Cables ........................ 877 13.6.4 Assume Every Fallen Wire Is Energized and Dangerous ................................................................. 877 13.6.4.1 Wire on Ground............................................. 877 13.6.4.2 Wire on Object ............................................... 877 13.6.4.3 Wire on Vehicle.............................................. 878 13.6.5 Never Cut Wires Except to Protect Life ....................... 878 13.6.5.1 Take Care after Cutting ................................ 878 13.6.5.2 Cutting Service Wires ................................... 878 13.6.6 Use Approved Procedures and Equipment If You Must Work Near Energized Facilities ............... 879 13.6.7 Avoid Using Hose Streams on Energized Facilities .........................................................880 13.6.8 Be Equally Alert Indoors and Outdoors ......................880 13.6.9 Protect People and Property in Surrounding Area and Do Not Fight Fires on Electric Equipment Until an Electric Company Representative Arrives ........ 881 13.6.10 Hose Streams May Be More Hazardous than Helpful Until Any Underground Fault Is De-Energized...................................................... 882 13.7 Effects of Electrical Shock.............................................................. 883 13.8 First Aid............................................................................................884 13.8.1 Shock ................................................................................. 885 13.8.2 Resuscitation..................................................................... 885 13.8.3 Resuscitation—Mouth-to-Mouth (Nose) Method ....... 886 13.8.4 Important Points to Remember ..................................... 886 13.8.5 Two-Victim Method of Resuscitation—Mouth-to Mouth (Nose) ....................................................................887 13.8.6 External Heart Compression .......................................... 887 Appendix A ............................................................................................... 889 Appendix B................................................................................................ 913 Bibliography .............................................................................................. 917 Index .......................................................................................................... 935DK4058_C000.indd xxvii 11/20/2008 10:17:58 AM
  • 28. DK4058_C000.indd xxviii 11/20/2008 10:17:58 AM
  • 29. Series Introduction When the first edition of this book was published 10 years ago, it was a particularly timely addition to the Marcel Dekker series on power system engineering. The power industry was beginning to be challenged by “aging infrastructures”—areas within local and regional power grids where a good deal of equipment was quite old and in a few cases much deteriorated. Maintenance, particularly testing to determine condition and prescribe proper service and refurbishment, was receiving more attention than it had in decades. But now, more than ever, there are factors beyond just the need to evaluate old equipment that are creating a heightened focus on sound maintenance and testing throughout the electric power industry. Equipment manufactur- ers have honed computer-aided design models to the point where they can shave design margins and engineer wear and deterioration rates with great precision, all to the purpose of reducing first cost, something they are forced to do in a world where much of the market buys mostly on the basis of lowest first cost. This means that comprehensive testing and “by the book” mainte- nance of equipment are critical earlier in the life cycle, because today’s new equipment has little margin for skipped maintenance or continued deterio- ration; it works well only if maintained in good condition. In addition, new materials, designs, and testing methods mean the proper matching of testing and maintenance to specific equipment is more intricate and involved than ever. New technologies like online condition monitoring create opportuni- ties to improve operations and efficiency. Finally, evolving concerns and standards, such as those regarding arc-flash, create a need for renewed focus in some areas. Electric Power Equipment Maintenance and Testing, Second Edition is a thorough update of the first edition, with revised material and additions throughout, including new discussions on arc-flash, online condition monitoring, uninter- ruptible power supply testing, motor vibration analysis, and current industry safety requirements to name just a few. In addition, it has two new chapters that provide enhanced focus on a pair of critical areas in power system testing: testing and commissioning of protective relays and instrument transformers; and power quality and harmonics, and their effects on electrical equipment. As the editor of the Power Engineering Series, I am proud to include Electric Power and Equipment Maintenance and Testing, Second Edition among this important group of books. During the past decade, I found the first edition to be among those I most often used in my work. This second edition is as well organized and indexed as the first, so that it will make a good reference in day-to-day work, with key material easy to find and concisely presented. Yet it is written in an accessible, linear style so that it is also a good tutorial xxixDK4058_C000.indd xxix 11/20/2008 10:17:58 AM
  • 30. xxx Series Introduction for those who are not familiar with the material. Since these are qualities I strive for in my books, I know how difficult it is for an author to achieve them well and as a result value Paul Gill’s new book all the more. Like all the books in the Power Engineering Series, Electric Power Equipment Maintenance and Testing, Second Edition puts modern technology in a context of proven, practical application; useful as a reference book as well as for self- study and advanced classroom use. The Power Engineering Series includes books covering the entire field of power engineering, in all of its specialties and subgenres, all aimed at providing practicing power engineers with the knowledge and techniques they need to meet the electric industry’s chal- lenges in the twenty-first century. H. Lee WillisDK4058_C000.indd xxx 11/20/2008 10:17:58 AM
  • 31. Foreword Paul Gill’s original book, Electrical Equipment Testing and Maintenance (1982), and the first edition, Electrical Power Equipment Maintenance and Testing published in 1997, were the first two books that addressed the practical aspects of electrical testing and maintenance of power system equipment and apparatus. Both books presented testing methodologies and engineering basics on the subject of electrical testing and maintenance in one volume. Considered the electrical test- ing and maintenance “bible,” Electrical Power Equipment Maintenance and Testing has been the leading treatise on the subject and an essential reference book for engineers and technicians concerned with the maintenance and testing of elec- trical power system equipme