Learn to correct icing and pollution problems in electrical line insulationWritten by prominent experts in the field, this book takes an in-depth look at the issues of electrical insulators for icing and polluted environments. It shows:Engineers and environmental specialists how to carry out appropriate insulator contamination measurements, understand how these readings change with time and weather, and work out how the readings compare with the upper limits set by insulator dimensions in their existing stationsDesign engineers how to assess the likely maximum pollution and icing limits at a substation or along an overhead line, and then select insulators that have appropriate withstand marginsRegulators why modest ice accretion at a moderate 0oC temperature on one occasion can qualify as a major reliability event day, while many similar days pass each winter without power system problemsEducators why the ice surface flashover is well behaved compared to the conventional pollution flashover, making it much more suitable for demonstrations, modeling, and analysisThe book is complemented with case studies and design equations to help readers identify the most appropriate insulators, bushings, and maintenance plans for their local conditions. Additionally, readers may download supplemental materials supporting evaluation of local climate and contamination.Insulators for Icing and Polluted Environments is indispensable reading for any professional who needs reliable electrical supply from networks exposed to sources of wetting and pollution. It also serves as an excellent introduction to the subjects of high-voltage surface flashover, environmental electrochemistry, and insulation coordination for researchers, professors, and students.
Author(s): Masoud Farzaneh, William A. Chisholm
Edition: 1
Year: 2009
Language: English
Pages: 680
INSULATORS FOR ICING AND POLLUTED ENVIRONMENTS......Page 5
CONTENTS......Page 7
PREFACE......Page 23
ACKNOWLEDGMENTS......Page 27
1.1. Scope and Objectives......Page 29
1.1.1. Problem Areas......Page 30
1.1.3. Intended Audience......Page 32
1.2.1. Measures of Power System Reliability......Page 34
1.2.3. Achieving Reliability with Maintenance......Page 38
1.2.5. Cost of Momentary Outages......Page 39
1.2.6. Who Is Responsible for Reliable Electrical Systems?......Page 41
1.3. The Insulation Coordination Process: What Is Involved?......Page 44
1.4. Organization of the Book......Page 45
References......Page 48
2.1. Terminology for Insulators......Page 51
2.1.3. Insulator Dimensions......Page 52
2.1.4. Interpretation of Terminology for Winter Conditions......Page 57
2.2. Classification of Insulators......Page 58
2.2.1. Classification by Ceramic or Polymeric Material......Page 59
2.2.2. Classification by Station or Line Application......Page 60
2.2.3. Classification by Nature of Mechanical Load......Page 62
2.3.1. Ceramic Materials......Page 63
2.3.2. Polymeric Materials......Page 72
2.3.3. End Fittings......Page 74
2.3.4. Other Materials in Series or Parallel with Insulators......Page 75
2.4. Electrical Stresses on Insulators......Page 76
2.4.1 Power Frequency Electrical Stresses......Page 77
2.4.2. Impulse Electrical Stresses......Page 78
2.4.3. Major Electrical Factors in Freezing Conditions......Page 79
2.5.1. Major Environmental Factors in Temperate Conditions......Page 80
2.5.2. Major Environmental Factors in Freezing Conditions......Page 81
2.6.2. Important Factors in Freezing Conditions......Page 82
2.7. Précis......Page 83
References......Page 84
3.1. Pollution: What It Is......Page 87
3.2.1. Typical Sources......Page 90
3.2.3. Monitoring Methods for Site Pollution Severity......Page 91
3.2.4. Short-Term Changes in Pollution Levels......Page 93
3.2.5. Cleaning Processes and Rates......Page 97
3.2.6. Long-Term Changes in Pollution Levels......Page 98
3.2.7. Other Factors in Pollution Problems......Page 99
3.3.2. Direct Measurement Method for NSDD......Page 100
3.3.3. Indirect Measurement Methods for NSDD......Page 101
3.3.5. Case Studies: NSDD Measurements......Page 103
3.4.1. Electrical Utility Sources......Page 106
3.4.2. Other Fixed Sources......Page 111
3.4.3. Conductance of Electrolytes......Page 119
3.5.1. Equivalent Conductance of Ions......Page 122
3.5.2. Effect of Temperature on Liquid Water Conductivity......Page 123
3.5.3. Effect of Temperature on Ice Conductivity......Page 125
3.6. Conversion to Equivalent Salt Deposit Density......Page 128
3.6.1. Insulator Case Study: Mexico......Page 129
3.6.4. Surface Resistance of Insulator......Page 131
3.6.6. Estimating ESDD from Environmental Measures for Corrosion......Page 134
3.6.7. Statistical Distribution of the Conductivity of Natural Precipitation......Page 138
3.6.8. Mobile Sources......Page 140
3.7. Self-Wetting of Contaminated Surfaces......Page 150
3.8.1. Fog Measurement Methods......Page 152
3.8.2. Typical Observations of Fog Parameters......Page 153
3.8.3. Fog Climatology......Page 155
3.8.4. Fog Deposition on Insulators......Page 156
3.8.5. Heat Balance Between Fog Accretion and Evaporation......Page 158
3.8.6. Critical Wetting Conditions in Fog......Page 159
3.9. Surface Wetting by Natural Precipitation......Page 160
3.9.1. Measurement Methods and Units......Page 161
3.9.2. Droplet Size and Precipitation Conductivity......Page 164
3.9.4. Rain Climatology......Page 165
3.10.3. Dam Spray......Page 167
3.10.4. Irrigation with Recycled Water......Page 169
3.10.5. Cooling Pond Overspray: Freshwater Makeup......Page 170
3.10.6. Cooling Tower Drift Effluent......Page 172
3.10.8. Manurigation......Page 173
3.11. Précis......Page 175
References......Page 176
4.1.1. Terms Related to Pollution and Its Characterization......Page 183
4.1.3. High-Voltage Measurement Terminology......Page 185
4.2.1. Air Breakdown in Uniform Field......Page 187
4.2.2. Air Breakdown in Nonuniform Field......Page 189
4.2.3. Breakdown of Clean and Dry Insulators......Page 190
4.2.4. Breakdown of Clean and Wet Insulators......Page 192
4.3.1. Breakdown Process on a Contaminated Hydrophilic Surface......Page 193
4.3.2. Breakdown Process on a Contaminated Hydrophobic Surface......Page 195
4.3.3. Complications in the Process for Real Insulators......Page 196
4.4.1. Field Observations of Leakage Current Activity......Page 197
4.4.2. Field Observations of Flashover Performance......Page 198
4.4.4. Observations at Croydon, United Kingdom, 1934–1936......Page 199
4.4.5. Observations at Croydon, United Kingdom, 1942–1958......Page 200
4.4.6. Observations at Brighton, United Kingdom......Page 203
4.4.9. Observations at Noto, Akita, and Takeyama, Japan......Page 204
4.5. Indoor Test Methods for Pollution Flashovers......Page 206
4.5.1. Comparison of Natural and Artificial Pollution Tests......Page 208
4.5.2. Power Supply Characteristics for Pollution Tests......Page 209
4.5.3. Electrical Clearances in Test Chamber......Page 212
4.6.2. Validation of Salt-Fog Test Method......Page 213
4.7. Clean-Fog Test Method......Page 215
4.7.1. Precontamination Process for Ceramic Insulators......Page 216
4.7.2. Precontamination Process for Nonceramic Insulators......Page 218
4.7.3. Artificial Wetting Processes......Page 220
4.7.4. Validation of Clean-Fog Test Method......Page 221
4.7.5. Rapid Flashover Voltage Technique......Page 223
4.8. Other Test Procedures......Page 224
4.8.2. Liquid Pollution Method......Page 225
4.8.4. Dry Salt Layer Method......Page 226
4.8.5. Cold-Fog Test Method......Page 227
4.8.6. Tests of Polymeric Insulator Material Endurance......Page 228
4.8.7. Summary of Pollution Test Methods......Page 229
4.9.1. ac Salt-Fog Test Results......Page 231
4.9.2. dc Salt-Fog Test Results......Page 232
4.10.1. ac Clean-Fog Tests......Page 233
4.10.2. dc Clean-Fog Tests......Page 235
4.10.3. Impulse Voltage Clean-Fog Tests......Page 237
4.11.1. Leakage Distance and Profile......Page 239
4.11.2. Effect of Small Diameter : Monofilaments and ADSS......Page 240
4.11.3. Influence of Average Insulator Diameter......Page 242
4.11.4. Influence of Insulator Form Factor......Page 247
4.11.5. Influence of Surface Material......Page 249
4.12. Effects of Nonsoluble Deposit Density......Page 251
4.13.1. Standard Correction for Air Density and Humidity......Page 252
4.13.2. Pressure Corrections for Contamination Flashovers......Page 255
4.14.1. Temperatures Above Freezing......Page 257
4.14.2. Temperatures Below Freezing......Page 259
4.15. Précis......Page 261
References......Page 262
5. CONTAMINATION FLASHOVER MODELS......Page 269
5.1. General Classification of Partial Discharges......Page 270
5.1.1. Discharges in the Presence of an Insulating Surface......Page 271
5.2.1. Wetted Layer Thickness and Electrical Properties......Page 274
5.2.3. Temperature Effects Leading to Dry-Band Formation......Page 275
5.2.4. Dry-Band Formation......Page 276
5.2.5. Arcing and Enlargement of Dry Bands......Page 277
5.2.6. Nuisance Factors from Discharges on Wetted Pollution Layers......Page 278
5.3. Electrical Arcing on Wet, Contaminated Surfaces......Page 283
5.3.2. Arc V–I Characteristics in Free Air......Page 284
5.3.3. Arc V–I Characteristics on Water or Ice Surfaces......Page 287
5.3.4. Dynamics of Arc Propagation......Page 289
5.4.1. Observations of Series Resistance of Pollution Layer......Page 290
5.4.2. Mathematical Functions for Series Resistance of Pollution Layer......Page 293
5.4.3. Resistance of Arc Root on Conducting Layer......Page 296
5.5.1. Analytical Solution: Uniform Pollution Layer......Page 299
5.5.2. Analytical Solution Using Insulator Form Factor......Page 301
5.5.4. Comparison of Different Models for Pollution Layer......Page 302
5.5.5. Introduction of Multiple Arcs in Series......Page 304
5.5.6. dc Arc Parameter Changes with Pressure and Temperature......Page 305
5.6.1. ac Arc Reignition......Page 306
5.6.2. ac Reignition Conditions Versus Ambient Temperature......Page 309
5.6.3. Mathematical Model for Reignition Condition......Page 310
5.6.4. Comparison of dc and ac Flashover Models......Page 311
5.7. Theoretical Modeling for Cold-Fog Flashover......Page 312
5.8. Future Directions for Pollution Flashover Modeling......Page 313
5.9. Précis......Page 314
References......Page 315
6. MITIGATION OPTIONS FOR IMPROVED PERFORMANCE IN POLLUTION CONDITIONS......Page 319
6.1.1. Insulator Pollution Monitoring......Page 320
6.1.2. Condition Monitoring Using Leakage Current......Page 324
6.1.3. Condition Monitoring Using Corona Detection Equipment......Page 329
6.1.4. Condition Monitoring Using Remote Thermal Monitoring......Page 331
6.2.1. Doing “Nothing”......Page 333
6.2.2. Insulator Washing: Selecting an Interval......Page 334
6.2.3. Insulator Washing: Methods and Conditions......Page 335
6.2.4. Case Study: Southern California Edison, 1965–1976......Page 337
6.2.5. Insulator Washing Using Industry Standard Practices......Page 338
6.2.6. Insulator Washing: Semiconducting Glaze......Page 341
6.2.7. Insulator Washing: Polymer Types and RTV Coatings......Page 342
6.2.9. Insulator Cleaning: Dry Media......Page 344
6.3.2. Greases......Page 347
6.3.3. Silicone Coatings......Page 349
6.4.1. Booster Sheds......Page 352
6.4.2. Creepage Extenders......Page 353
6.4.3. Animal, Bird or “Guano” Guards......Page 355
6.4.4. Corona Rings......Page 357
6.4.5. Arcing Horns......Page 359
6.6. Changing to Improved Designs......Page 360
6.6.1. Anti-Fog Disk Profile with Standard Spacing and Diameter......Page 362
6.6.2. Aerodynamic Disk Profile......Page 363
6.6.3. Alternating Diameter Profiles......Page 365
6.6.4. Bell Profile with Larger Diameter and Spacing......Page 366
6.6.5. Anti-Fog Disk Profiles with Larger Diameter and Spacing......Page 368
6.6.6. Station Post and Bushing Profiles......Page 370
6.7.1. Semiconducting Glaze Technology......Page 371
6.7.2. Heat Balance: Clean Semiconducting Glaze Insulators......Page 373
6.7.3. Heat Balance: Contaminated Semiconducting Glaze Insulators......Page 376
6.7.4. On-Line Monitoring with Semiconducting Glaze Insulators......Page 377
6.7.5. Role of Power Dissipation in Fog and Cold-Fog Accretion......Page 378
6.7.6. Considerations for Semiconducting Insulators in Close Proximity......Page 379
6.8. Changing to Polymer Insulators......Page 380
6.8.1. Short-Term Experience in Contaminated Conditions......Page 381
6.8.2. Long-Term Performance in Contaminated Conditions......Page 382
6.8.3. Interchangeability with Ceramic Insulators......Page 383
6.9. Précis......Page 385
References......Page 386
7. ICING FLASHOVERS......Page 391
7.1. Terminology for Ice......Page 392
7.2.1. Crystal Structure......Page 393
7.2.2. Supercooling......Page 394
7.3. Electrical Characteristics of Ice......Page 395
7.3.2. Conductivity of Ice Surface......Page 396
7.3.3. High-Frequency Behavior of Ice......Page 399
7.4. Ice Flashover Experience......Page 401
7.4.1. Very Light Icing......Page 402
7.4.2. Light Icing......Page 405
7.4.3. Moderate Icing......Page 408
7.4.4. Heavy Icing......Page 409
7.5. Ice Flashover Processes......Page 412
7.5.1. Icing Flashover Process for Very Light and Light Ice Accretion......Page 413
7.5.2. Icing Flashover for Moderate Ice Accretion......Page 414
7.5.3. Icing Flashover Process for Heavy Ice Accretion......Page 415
7.6. Icing Test Methods......Page 416
7.6.1. Standard Electrical Tests of Insulators......Page 417
7.6.3. Natural Icing Tests in Outdoor Test Stations......Page 418
7.6.4. History of Laboratory Ice Testing......Page 419
7.6.5. Recommended Icing Test Method......Page 426
7.6.6. Recommended Cold-Fog Test Method......Page 430
7.7.2. Laboratory Tests with Very Light Icing......Page 431
7.7.3. Insulators with Light Ice Accretion......Page 434
7.7.4. Insulators with Moderate Ice Accretion......Page 436
7.7.5. Insulators Fully Bridged with Ice......Page 443
7.7.7. Ice Flashover Under Switching and Lightning Surge......Page 450
7.7.8. Effect of Diameter on ac Flashover for Heavy Icing......Page 453
7.7.9. dc Flashover Results for Heavy Icing......Page 455
7.8. Empirical Models for Icing Flashovers......Page 459
7.8.1. The Icing Stress Product for ac Flashover Across Leakage Distance......Page 460
7.8.2. The Icing Stress Product for ac Flashover across Dry Arc Distance......Page 462
7.8.3. Implementation of ISP Model for dc Flashover Under Heavy Ice Conditions......Page 467
7.8.4. Comparison of Ice Flashover to Wet Flashover......Page 468
7.9. Mathematical Modeling of Flashover Process on Ice-Covered Insulators......Page 469
7.9.1. dc Flashover Modeling of Ice-Covered Insulators......Page 470
7.9.2. Influence of Insulator Precontamination on dc Flashover of Ice-Covered Insulators......Page 476
7.9.3. ac Flashover Modeling of Ice-Covered Insulators......Page 478
7.9.4. Application Details: Flashover Under Very Light Icing......Page 485
7.9.5. Application Details: Flashover Under Light Icing Conditions......Page 487
7.9.6. Application Details: Flashover Under Moderate Icing Conditions......Page 489
7.9.7. Application Details: Flashover Under Heavy Icing Conditions......Page 491
7.10.1. Pressure Correction for Heavy Ice Tests......Page 493
7.10.3. Heat Transfer and Ice Temperature......Page 495
7.11. Future Directions for Icing Flashover Modeling......Page 497
7.11.2. Dynamics of Arc Motion on Ice Surfaces......Page 498
7.11.3. Dynamic Model for Ice Temperature......Page 499
References......Page 500
8.1. Terminology for Snow......Page 509
8.2. Snow Morphology......Page 510
8.3. Snow Electrical Characteristics......Page 512
8.3.1. Electrical Conduction in Snow, dc to 100 Hz......Page 515
8.3.2. Dielectric Behavior of Snow, 100 Hz to 5 MHz......Page 517
8.4. Snow Flashover Experience......Page 518
8.5. Snow Flashover Process and Test Methods......Page 521
8.5.1. Snow Flashover Process......Page 522
8.5.2. Snow Test Methods......Page 523
8.5.3. General Arrangements for Snow Tests......Page 524
8.5.4. Snow Deposit Methods......Page 525
8.5.5. Evaluation of Flashover Voltage for Snow Tests......Page 526
8.6.1. Outdoor Tests Using Natural Snow Accretion......Page 528
8.6.3. Indoor Tests Using Natural Snow Deposits......Page 531
8.6.5. Snow Flashover Under Switching Surge......Page 533
8.7 Empirical Model for Snow Flashover......Page 536
8.7.1. Conversion of Test Results to Snow Stress Product......Page 537
8.7.2. Comparison of Snow Flashover to Ice and Cold Fog......Page 539
8.7.3. Comparison of Snow Flashover to Normal Service Voltage......Page 540
8.8. Mathematical Modeling of Flashover Process on Snow-Covered Insulators......Page 541
8.8.1. Voltage–Current Characteristics in Snow......Page 542
8.8.2. dc Flashover Voltage......Page 545
8.8.3. ac Reignition Condition and Flashover Voltage......Page 546
8.8.4. Switching and Lightning Surge Flashover......Page 547
8.10.1. In-Cloud Rime Accretion: Keele Valley, Ontario......Page 548
8.10.2. Temporary Overvoltage Problem: 420-kV Breaker in Norway......Page 550
8.10.3. Snow Accretion on Surge Arresters......Page 552
References......Page 553
9. MITIGATION OPTIONS FOR IMPROVED PERFORMANCE IN ICE AND SNOW CONDITIONS......Page 557
9.1. Options for Mitigating Very Light and Light Icing......Page 558
9.1.1. Semiconducting Glaze......Page 560
9.1.2. Increased Leakage Distance......Page 563
9.1.3. Coating of Insulators with RTV Silicone......Page 567
9.1.4. Change for Polymer......Page 571
9.1.5. Insulator Pollution Monitoring and Washing......Page 572
9.1.6. Case Study: SMART Washing......Page 576
9.2. Options for Mitigating Moderate Icing......Page 578
9.2.1. Use of Profiles with Greater Shed-to-Shed Distance......Page 580
9.2.2. Increased Dry Arc Distance......Page 581
9.2.4. Semiconducting Glaze......Page 583
9.2.5. Polymer Insulators......Page 587
9.2.7. Condition Monitoring Using Remote Thermal Measurements......Page 589
9.2.8. Silicone Coatings......Page 590
9.3.1. Increasing the Dry Arc Distance......Page 592
9.3.2 Changing to Semiconducting Glaze......Page 594
9.3.3. Adding Booster Sheds......Page 596
9.3.4. Changing to Polymer Insulators......Page 600
9.3.5. Ice Monitoring Using Leakage Current......Page 601
9.3.6. Ice Stripping in Freezing Weather......Page 603
9.3.7. Corona Rings and Other Hardware......Page 604
9.3.9. Coating of Insulators with RTV Silicone......Page 605
9.4.2. Insulator Profile......Page 608
9.4.3. Insulators in Parallel......Page 609
9.4.4. Polymer Insulators......Page 610
9.4.7. Use of Accessories......Page 611
9.5.1. Doing “Nothing”......Page 612
9.6. Précis......Page 613
References......Page 614
10. INSULATION COORDINATION FOR ICING AND POLLUTED ENVIRONMENTS......Page 619
10.1.1. Classification of Overvoltage Stresses on Transmission Lines......Page 620
10.1.2. High-Voltage Insulator Parameters......Page 622
10.1.3. Extra-High-Voltage Insulator Parameters......Page 623
10.1.4. Design for an Acceptable Component Failure Rate......Page 624
10.1.5. Design for an Acceptable Network Failure Rate......Page 626
10.2. Deterministic and Probabilistic Methods......Page 627
10.3. IEEE 1313.2 Design Approach for Contamination......Page 632
10.4. IEC 60815 Design Approach for Contamination......Page 634
10.5. CIGRE Design Approach for Contamination......Page 635
10.6. Characteristics of Winter Pollution......Page 639
10.6.2. Rate of Increase of ESDD......Page 640
10.6.3. Effect of Road Salt......Page 643
10.7. Winter Fog Events......Page 645
10.8.1. Measurement Units......Page 646
10.8.2. Frequency of Occurrence......Page 647
10.8.4. Severity of Freezing Rain Occurrence......Page 650
10.8.5. Electrical Conductivity of Freezing Rainwater......Page 651
10.9.2 Snow Accumulation and Persistence......Page 653
10.9.3. Snow Melting......Page 656
10.10. Deterministic Coordination for Leakage Distance......Page 657
10.11. Probabilistic Coordination for Leakage Distance......Page 658
10.12.1. Dry Arc Distance Requirements for Icing Conditions......Page 659
10.12.2. Dry Arc Requirements for Snow Conditions......Page 660
10.13. Probabilistic Coordination for Dry Arc Distance......Page 662
10.14.1. Ontario 500 kV......Page 663
10.14.2. Ontario 230 kV......Page 665
10.14.3. Newfoundland and Labrador Hydro......Page 668
10.15. Précis......Page 669
References......Page 670
APPENDIX A: MEASUREMENT OF INSULATOR CONTAMINATION LEVEL......Page 673
APPENDIX B: STANDARD CORRECTIONS FOR HUMIDITY, TEMPERATURE, AND PRESSURE......Page 679
APPENDIX C: TERMS RELATED TO ELECTRICAL IMPULSES......Page 687
INDEX......Page 689
