Bin Cao, PhD, is an Assistant Professor at the Institute of Advanced Technologies in Energy and Electrical Engineering at Tsinghua University, China. He has published 80 peer-reviewed journal papers and received the 2024 Geneva Invention Exhibition Gold Award. Dr. Cao is an active member of CIGRE NGN, the Chinese Insulator Standardization Technical Committee, and the IEEE PES High Voltage Surface Discharge Technical Committee. Liming Wang, PhD, is the Director of the Institute of Advanced Technologies in Energy and Electrical Engineering and a full professor at Tsinghua University, China. He has authored over 760 peer-reviewed papers, including 104 in IEEE Transactions journals, and holds 128 patents. Professor Wang serves as Chair of the IEEE DEIS Technical Committee on Discharges in Gas at UHV, Vice Chair of the China Electric Power Insulator Standardization Committee and was the recipient of the 2024 IEEE DEIS Caixin Sun and Stan Gryzbowski Lifetime Achievement Award.

• List of Figures ixList of Tables xixAbout the Authors xxiPreface xxiiiAcknowledgments xxvAcronyms xxvii1 Challenges in Insulation of Transmission Equipment with Climate Change 11.1 Classical Theories of Pollution Discharge on Insulators 31.2 Insulator Contamination 61.3 Insulator Wetting 91.4 Characterization Parameters for External Insulation 111.5 Pollution Monitoring Technology 151.6 Main Content of the Book 172 Wetting Behavior of Insulator Contamination at Saturated Humidity 212.1 Introduction 212.2 Example Arrangement 222.3 Results 302.4 Impact of Non-soluble Deposit Density (NSDD) and Surface Angle 342.5 Summary 383 Soluble Salt Dissolution in Contaminated Layers 413.1 Introduction 413.2 Experimental Arrangement 423.3 Results 473.4 Relationship Between ESDD and Conductivity 503.5 Summary 594 Wetting Behavior of Insulator Contamination at Unsaturated Humidity 634.1 Introduction 634.2 Experimental Arrangement 644.3 Results 724.4 Relationship Between Humidity, Contamination, and Leakage Current 784.5 Summary 855 Temperature Differences and Their Effect on Wetting Behavior 895.1 Introduction 895.2 Experimental Arrangement 905.3 Results 965.4 Summary 1036 Characterization of Salt Fog Environments and Its Effect on the Outdoor Insulation 1076.1 Introduction 1076.2 ESSC 1086.3 Results 1136.4 Comprehensive Model for Predicting Flashover Voltage in the Salt Fog Environments 1196.5 Summary 1247 Effect of Hydrophobicity on the Contamination Wetting 1277.1 Introduction 1277.2 Experimental Arrangement 1287.3 Results 1327.4 Dissolving Characteristics of Soluble Salts at Water Drop and Dry Band 1357.5 Summary 1408 Wetting Characteristics of the Hydrophobic Material Surface Through Condensation 1438.1 Introduction 1438.2 Experimental Arrangement 1448.3 Results 1508.4 Discussion 1548.5 Summary 1589 Flashover Characteristics of Hydrophobic Surfaces with Different Wetting Degree 1619.1 Introduction 1619.2 Flashover Characteristics with Lower Wetting Degree 1629.3 Flashover Characteristics with Higher Wetting Degree 1709.4 Discussion of Surface Flashover with Water Involved 1779.5 Summary 18410 Factors Influencing the Hydrophobic Surface Flashover and Their Application 18710.1 Introduction 18710.2 Wetting Prerequisite of Flashover on Hydrophobic Surface 18710.3 Effect of Contamination on Flashover Voltage Under Different Wetting Conditions 19010.4 Dynamic Behavior of Water Droplets Under Electric Field 19210.5 Replacement and Maintenance Strategies for Degraded Hydrophobic Insulators 20010.6 Summary 20211 Insulator Contamination Monitoring Based on Its Hygroscopicity Under Unsaturated Humidity 20511.1 Introduction 20511.2 Development of Online Monitoring Devices 20611.3 System Application 20811.4 Algorithms for Real-time Contamination Assessment 21011.5 Assessment Method of Pollution Degree for Hydrophobic Surface 21611.6 Summary 22212 Insulator Contamination Monitoring at Saturated Moisture 22512.1 Introduction 22512.2 Test Specimens, Facilities, and Procedure 22612.3 Experimental Results 22912.4 Analyses and Discussion 23312.5 Influence of Partial Electric Arc on the Contamination Monitoring in View of Leakage Current 23612.6 Summary 24013 Spatial and Temporal Analysis of Contamination on Insulator Surfaces 24313.1 Introduction 24313.2 Artificial Contamination Test 24413.3 Contamination Components of Actual Operating Insulators 24913.4 Summary 25714 Correction Methods for Soluble Salt Components in Contamination Assessment 26114.1 Introduction 26114.2 Analysis of Surface Conductivity for Soluble Salt Detection 26214.3 Correction Method for Soluble Salt Components and Equipment 26814.4 Experimental Validation of Correction Methods 27214.5 Engineering Implications 27514.6 Summary 277Index 281

Bin Cao, PhD, is an Assistant Professor at the Institute of Advanced Technologies in Energy and Electrical Engineering at Tsinghua University, China. He has published 80 peer-reviewed journal papers and received the 2024 Geneva Invention Exhibition Gold Award. Dr. Cao is an active member of CIGRE NGN, the Chinese Insulator Standardization Technical Committee, and the IEEE PES High Voltage Surface Discharge Technical Committee. Liming Wang, PhD, is the Director of the Institute of Advanced Technologies in Energy and Electrical Engineering and a full professor at Tsinghua University, China. He has authored over 760 peer-reviewed papers, including 104 in IEEE Transactions journals, and holds 128 patents. Professor Wang serves as Chair of the IEEE DEIS Technical Committee on Discharges in Gas at UHV, Vice Chair of the China Electric Power Insulator Standardization Committee and was the recipient of the 2024 IEEE DEIS Caixin Sun and Stan Gryzbowski Lifetime Achievement Award.

• List of Figures ixList of Tables xixAbout the Authors xxiPreface xxiiiAcknowledgments xxvAcronyms xxvii1 Challenges in Insulation of Transmission Equipment with Climate Change 11.1 Classical Theories of Pollution Discharge on Insulators 31.2 Insulator Contamination 61.3 Insulator Wetting 91.4 Characterization Parameters for External Insulation 111.5 Pollution Monitoring Technology 151.6 Main Content of the Book 172 Wetting Behavior of Insulator Contamination at Saturated Humidity 212.1 Introduction 212.2 Example Arrangement 222.3 Results 302.4 Impact of Non-soluble Deposit Density (NSDD) and Surface Angle 342.5 Summary 383 Soluble Salt Dissolution in Contaminated Layers 413.1 Introduction 413.2 Experimental Arrangement 423.3 Results 473.4 Relationship Between ESDD and Conductivity 503.5 Summary 594 Wetting Behavior of Insulator Contamination at Unsaturated Humidity 634.1 Introduction 634.2 Experimental Arrangement 644.3 Results 724.4 Relationship Between Humidity, Contamination, and Leakage Current 784.5 Summary 855 Temperature Differences and Their Effect on Wetting Behavior 895.1 Introduction 895.2 Experimental Arrangement 905.3 Results 965.4 Summary 1036 Characterization of Salt Fog Environments and Its Effect on the Outdoor Insulation 1076.1 Introduction 1076.2 ESSC 1086.3 Results 1136.4 Comprehensive Model for Predicting Flashover Voltage in the Salt Fog Environments 1196.5 Summary 1247 Effect of Hydrophobicity on the Contamination Wetting 1277.1 Introduction 1277.2 Experimental Arrangement 1287.3 Results 1327.4 Dissolving Characteristics of Soluble Salts at Water Drop and Dry Band 1357.5 Summary 1408 Wetting Characteristics of the Hydrophobic Material Surface Through Condensation 1438.1 Introduction 1438.2 Experimental Arrangement 1448.3 Results 1508.4 Discussion 1548.5 Summary 1589 Flashover Characteristics of Hydrophobic Surfaces with Different Wetting Degree 1619.1 Introduction 1619.2 Flashover Characteristics with Lower Wetting Degree 1629.3 Flashover Characteristics with Higher Wetting Degree 1709.4 Discussion of Surface Flashover with Water Involved 1779.5 Summary 18410 Factors Influencing the Hydrophobic Surface Flashover and Their Application 18710.1 Introduction 18710.2 Wetting Prerequisite of Flashover on Hydrophobic Surface 18710.3 Effect of Contamination on Flashover Voltage Under Different Wetting Conditions 19010.4 Dynamic Behavior of Water Droplets Under Electric Field 19210.5 Replacement and Maintenance Strategies for Degraded Hydrophobic Insulators 20010.6 Summary 20211 Insulator Contamination Monitoring Based on Its Hygroscopicity Under Unsaturated Humidity 20511.1 Introduction 20511.2 Development of Online Monitoring Devices 20611.3 System Application 20811.4 Algorithms for Real-time Contamination Assessment 21011.5 Assessment Method of Pollution Degree for Hydrophobic Surface 21611.6 Summary 22212 Insulator Contamination Monitoring at Saturated Moisture 22512.1 Introduction 22512.2 Test Specimens, Facilities, and Procedure 22612.3 Experimental Results 22912.4 Analyses and Discussion 23312.5 Influence of Partial Electric Arc on the Contamination Monitoring in View of Leakage Current 23612.6 Summary 24013 Spatial and Temporal Analysis of Contamination on Insulator Surfaces 24313.1 Introduction 24313.2 Artificial Contamination Test 24413.3 Contamination Components of Actual Operating Insulators 24913.4 Summary 25714 Correction Methods for Soluble Salt Components in Contamination Assessment 26114.1 Introduction 26114.2 Analysis of Surface Conductivity for Soluble Salt Detection 26214.3 Correction Method for Soluble Salt Components and Equipment 26814.4 Experimental Validation of Correction Methods 27214.5 Engineering Implications 27514.6 Summary 277Index 281