High Voltage and Electrical Insulation Engineering

Ravindra Arora, Dr.-Ing. from TU Dresden, Germany is a Senior Life Member of IEEE and a Life Member of the Institution of Engineers (India). He worked at the Indian Institute of Technology Kanpur (IITK) for 34 years, retiring in 2008. While at IITK, he established a unique high voltage laboratory where he conducted research activity and several industry-sponsored projects. Dr. Arora has over five decades of experience with industry, education, and research where he is still active. His special field of research interest has been “lightning”.Wolfgang Mosch, Dr.-Ing. habil. retired as Head and Chair Professor of the Institute of High Voltage Technology, Electrical Engineering (Power) Division of Technical University Dresden, Germany in 1993. He has been actively involved with practical research in high voltage and insulation engineering for five decades working with both industry and academia since 1960. He has authored a number of books on the subject in German and English languages.

• Author Biographies xvPreface xixAcknowledgments xxiii1 Introduction 11.1 Electric Charge, Discharge, Current, and Potential 21.2 Electric and Magnetic Fields 41.3 Electromagnetism 41.4 Dielectric and Electrical Insulation 61.5 Electrical Breakdown 61.5.1 Global Breakdown 71.5.2 Local Breakdown or Partial Breakdown 71.5.3 Breakdown Strength or Electric Strength 71.6 Corona, Streamer, Star, and Leader 71.6.1 Aurora 91.6.2 Electric Arc 101.7 Capacitance and Capacitor 101.7.1 Stray Capacitance 111.8 Forms of Voltages and Currents 121.8.1 TravelingWaves 131.8.2 Neutral and Ground 13References 132 Electric Fields, Their Control and Estimation 152.1 Electric Field Intensity, “E” 152.2 Breakdown and Electric Strength of Dielectrics, “Eb” 182.2.1 Partial Breakdown in Dielectrics 182.3 Classification of Electric Fields 192.3.1 Degree of Uniformity of Electric Fields 212.3.1.1 Effect of Grounding on Field Configuration 232.4 Control of Electric Field Intensity (Stress Control) 252.5 Estimation of Electric Field Intensity 302.5.1 Basic Equations for Potential and Field Intensity in Electrostatic Fields 312.5.2 Analytical Methods for the Estimation of Electric Field Intensity in Homogeneous Isotropic Single Dielectric 342.5.2.1 Direct Solution of Laplace Equation 352.5.2.2 “Gaussian Surface” Enclosed Charge Techniques for the Estimation and Optimization of Field 392.5.3 Analysis of Electric Field Intensity in Isotropic Multidielectric System 462.5.3.1 Field with Longitudinal Interface 462.5.3.2 Field with Perpendicular Interface 482.5.3.3 Field with Diagonal Interface 532.5.4 Numerical Methods for the Estimation of Electric Field Intensity 542.5.4.1 Finite Element Method (FEM) 552.5.4.2 Charge Simulation Method (CSM) 622.5.5 Numerical Optimization of Electric Fields 692.5.5.1 Optimization by Displacement of Contour Points 702.5.5.2 Optimization by Changing the Positions of Optimization Charges and Contour Points 712.5.5.3 Optimization by Modification of “Contour Elements” 732.6 Conclusion 75References 763 Field Dependent Behavior of Air and Other Gaseous Dielectrics 793.1 Fundamental Process of Field Assisted Generation of Charge Carriers 833.1.1 Impact Ionization 853.1.2 Thermal Ionization 863.1.3 Photoionization and Interaction of Metastables with Molecules 863.2 Breakdown of Atmospheric Air in Uniform andWeakly Nonuniform Fields 883.2.1 Uniform Field with Space Charge 893.2.2 Development of Electron Avalanche 913.2.3 Development of Streamer or “Kanal Discharge” 963.2.4 Breakdown Mechanisms 993.2.4.1 Breakdown in Uniform Fields with Small Gap Distances (Townsend Mechanism) 993.2.4.2 Breakdown with Streamer (Streamer or Kanal Mechanism) 1063.2.5 Breakdown Voltage Characteristics in Uniform Fields (Paschen’s Law) 1113.2.6 Breakdown Voltage Characteristics inWeakly Nonuniform Fields 1223.3 Breakdown in Extremely Nonuniform Fields and Corona 1233.3.1 Development of Avalanche Discharge of Below Critical Amplification 1243.3.1.1 Positive Needle–Plane Electrode Configuration (Positive or Anode Star Corona) 1253.3.1.2 Negative Needle–Plane Electrode Configuration (Negative or Cathode Star Corona) 1273.3.2 Development of Streamer or Kanal Discharge 1293.3.2.1 Positive Rod–Plane Electrode (Positive Streamer Corona) 1293.3.2.2 Negative Rod–Plane Electrode (Negative Streamer Corona) 1343.3.2.3 Symmetrical Positive and Negative Electrode Configurations in Extremely Nonuniform Fields 1363.3.3 Development of Stem and Leader Corona 1373.3.3.1 Development and Propagation of Positive Leader Corona 1413.3.3.2 Development and Propagation of Negative Leader Corona and the Phenomenon of Space Leader 1443.3.3.3 Electromagnetic Interference (EMI) Produced by Corona 1473.3.4 Summary of the Development of Breakdown in Extremely Nonuniform Fields 1483.3.5 Breakdown Voltage Characteristics of Air in Extremely Nonuniform Fields 1503.3.5.1 Breakdown Preceded with Stable Star Corona 1523.3.5.2 Breakdown Preceded with Stable Streamer Corona 1563.3.5.3 Breakdown Preceded with Stable Streamer and Leader Coronas (Long Air Gaps) 1633.3.5.4 The Requirement of Time for the Formation of Spark Breakdown with Impulse Voltages 1683.3.5.5 Effect of Wave Shape on Breakdown with Impulse Voltages 1713.3.5.6 Conclusions from Measured Breakdown Characteristics in Extremely Nonuniform Fields 1753.3.5.7 Estimation of Breakdown Voltage in Extremely Nonuniform Fields in Long Air Gaps 1763.3.6 Effects of Partial Breakdown or Corona in Atmospheric Air 1783.3.6.1 Chemical Decomposition of Air by Corona 1793.3.6.2 Corona Power Loss in Transmission Lines 1823.3.6.3 Electromagnetic Interference (EMI) and Audible Noise (AN) Produced by Power System Network 1843.3.6.4 Other Effects of High Voltage Transmission Lines and Corona on the Environment 1873.4 Electric Arcs and Their Characteristics 1883.4.1 Static Voltage–Current, U–I, Characteristics of Arcs in Air 1893.4.2 Dynamic U–I Characteristics of Arcs 1923.4.3 Extinction of Arcs 1943.5 Properties of Sulfurhexafluoride, SF6, Gas, and Its Application in Electrical Installations 1943.5.1 Properties of Sulfurhexafluoride, SF6 Gas 1973.5.1.1 Physical Properties 1993.5.1.2 Property of Electron Attachment 1993.5.2 Breakdown in Uniform and Weakly Nonuniform Fields with SF6 Insulation 2013.5.3 External Factors Affecting Breakdown Characteristics in Compressed Gases 2103.5.3.1 Effect of Electrode Materials and Their Surface Roughness on Breakdown 2103.5.3.2 Effect of Particle Contaminants in Gas Insulated Systems (GIS) 2123.5.3.3 Particle Initiated PB and Breakdown Measurements in GIS 2193.5.3.4 Preventive Measures for the Effect of Particles in GIS 2223.5.4 Breakdown in Extremely Nonuniform and Distorted Weakly Nonuniform Fields with Stable PB in SF6 Gas Insulation 2223.5.5 Electrical Strength of Mixtures of SF6 with Other Gases 2263.5.6 Decomposition of SF6 and Its Mixtures in Gas Insulated Equipment 2303.5.7 SF6 Gas and Environment 2343.5.8 Development in Gas Insulated Power Apparatus 2363.5.9 Mineral Oils Versus SF6 Gas 2363.5.10 Basic Electrical Insulation Requirements for GITs 2383.5.11 SF6 Gas Insulation, a Replacement for Oils 2393.5.12 Basic Cooling Requirements Met by Gas for GITs 2403.5.13 Environment Concerns and Future Trends 2413.6 Investigations for the Requirement of Optimum Clearance for 25 kV Electric Traction: A Case Study 2423.6.1 Field Estimation for the Traction Overhead Conductor at 25 kV 2433.6.2 Measurement of Breakdown/Withstand Voltage Characteristics 2473.6.3 Measurements with ac Power Frequency Voltage 2473.6.4 Measurements Under FairWeather, Natural Fog, and Natural Rain Conditions 2483.6.5 Measurements Under Artificial Rain 2493.6.6 Investigation of the Performance of Air-Gap Under System Overvoltages 2503.6.7 Measurements with Impulse Voltages 2523.6.8 Measurements with Insulating-Barrier in the Gap 2533.6.9 Choice of Solid Insulating Barrier 2533.6.10 Positioning and Fastening of the Solid Insulating Barrier in the Gap 2543.6.11 Measurement Results with Teflon Sheet as a Barrier 2543.7 Conclusions and Recommendations 255References 2574 Lightning and Ball Lightning, Development Mechanisms, Deleterious Effects, Protection 2674.1 The Globe, a Capacitor 2684.1.1 The Earth’s Atmosphere and the Clouds 2694.1.1.1 The Troposphere 2704.1.1.2 The Stratosphere 2704.1.1.3 The Ionosphere 2714.1.2 Clouds and Their Important Role 2714.1.2.1 Classification of Clouds 2714.1.3 Static Electric Charge in the Atmosphere 2734.1.3.1 External Source of Electric Charge 2734.1.3.2 Charges Due to Ionization Within the Atmospheric Air 2754.1.3.3 Charging Mechanisms and Thunderstorms 2764.2 Mechanisms of Lightning Strike 2784.2.1 Mechanism of Breakdown in Long Air Gap 2784.2.2 Mechanisms of Lightning Strike on the Ground 2804.2.3 Preference of Locations for the Lightning to Strike 2824.3 Deleterious Effects of Lightning 2844.3.1 Loss of Life of the Living Beings 2844.3.2 Fire Hazards Due to Lightning 2844.3.3 Blast Created by Lightning 2854.3.4 Development of Transient Over-Voltage Due to Lightning Strike on the Electric Power System Network and Its Protection 2864.4 Protection from Lightning 2884.4.1 Protection of Lives 2894.4.2 Protection of Buildings and Structures 2904.4.2.1 Air Termination Network 2914.4.2.2 Down Conductor 2924.4.2.3 Earth Termination System 2924.4.3 The Protected Area 2924.4.3.1 Protected Volume Determined by a Cone 2924.4.3.2 Protected Volume Evolved by Rolling a Sphere 2934.5 Ball Lightning 2954.5.1 The Phenomenon of Ball Lightning 2954.5.2 Injurious Effects of Ball Lightning 2964.5.3 Models and Physics of Ball Lightning 2964.5.4 Ball Lightning Without Lightning Strike 2984.5.4.1 TheWeather and Climatic Conditions 2994.5.4.2 The Man Made Sources of Charge/Current 2994.5.5 Ball Lightning, a Mythological Legend in India 3004.6 Lightning, a Truthful Myth 3014.6.1 Examples of Known and Widely Accepted Myths 3014.6.2 The Mythology of “Bijli Mahadev” 3024.6.3 Geographical Location and the Construction of the Temple 3024.6.4 The Mechanism of Destruction of the Deity 304References 3045 Electrical Properties of Vacuum as High Voltage Insulation 3075.1 Pre-breakdown Electron Emission in Vacuum 3085.1.1 Mechanism of Electron Emission from Metallic Surfaces 3085.1.2 Non-metallic Electron Emission Mechanisms 3115.2 Pre-breakdown Conduction and Spark Breakdown in Vacuum 3165.2.1 Electrical Breakdown in Vacuum Interrupters 3245.2.1.1 High Current Arc Quenching in Vacuum 3245.2.1.2 Delayed Re-ignition of Arcs 3255.2.1.3 Effect of Insulator Surface Phenomena 3265.2.2 Effect of Conditioning of Electrodes on Breakdown Voltage 3265.2.3 Effect of Area of Electrodes on Breakdown in Vacuum 3285.3 Vacuum as Insulation in Space Applications 3295.3.1 Vacuum-Insulated Power Supplies for Space 3295.3.2 Vacuum Related Problems in Low Earth Orbit Plasma Environment 3305.4 Development in Vacuum Technology Applications in Power System Switchgears 3315.4.1 Development in Actuator Mechanism for the Interrupter Units 3335.4.2 Development of 245 kV Vacuum Circuit Breaker 3345.5 Conclusion 335References 3366 Liquid Dielectrics, Their Classification, Properties, and Breakdown Strength 3396.1 Classification of Liquid Dielectrics 3406.1.1 Mineral Insulating Oils 3416.1.1.1 Mineral Insulating Oil in Transformers 3426.1.2 Vegetable Oils 3446.1.3 Synthetic Liquid Dielectrics, the Chlorinated Diphenyls 3446.1.3.1 Halogen-Free Synthetic Oils 3456.1.4 Inorganic Liquids as Insulation 3466.1.5 Polar and Nonpolar Dielectrics 3476.2 Dielectric Properties of Insulating Materials 3476.2.1 Insulation Resistance Offered by Dielectrics 3476.2.2 Permittivity of Insulating Materials 3496.2.3 Polarization in Insulating Materials 3506.2.3.1 Effect of Time on Polarization 3526.2.3.2 Polarization Under Alternating Voltages and the Eigen-Frequency of Dielectrics 3556.2.3.3 High Frequency High Voltage Application of Dielectrics 3586.2.4 Dielectric Power Losses in Insulating Materials 3606.3 Breakdown in Liquid Dielectrics 3636.3.1 Electric Conduction in Insulating Liquids 3646.3.1.1 Liquid Dielectrics in Motion and Electrohydrodynamics (EHD) 3676.3.2 Intrinsic Breakdown Strength 3696.3.3 Practical Breakdown Strength Measurement at Near Uniform Fields 3706.3.3.1 Effect of Moisture and Temperature on Breakdown Strength 3726.3.4 Breakdown in Extremely Nonuniform Fields and the Development of Streamer 3766.4 Aging in Mineral Insulating Oils 382References 3847 Solid Dielectrics, Their Sources, Properties, and Behavior in Electric Fields 3877.1 Classification of Solid Insulating Materials 3887.1.1 Inorganic Insulating Materials 3887.1.1.1 Ceramic Insulating Materials 3887.1.1.2 Glass as an Insulating Material 3927.1.2 Polymeric Organic Materials 3927.1.2.1 Thermoplastic Polymers 3937.1.2.2 Thermoset Polymers 3937.1.2.3 Polymer Compounds 3947.1.2.4 Polyvinylchloride (PVC) 3947.1.2.5 Polyethylene (PE) 3957.1.2.6 Epoxy Resins (EP-Resins) 4007.1.2.7 Natural and Synthetic Rubber 4027.1.3 Composite Insulating System 4037.1.3.1 Impregnated Paper as a Composite Insulation System 4037.1.3.2 Insulating Board Materials 4077.1.3.3 Fiber Reinforced Plastics (FRP) 4077.2 Partial Breakdown in Solid Dielectrics 4087.2.1 Internal Partial Breakdown 4097.2.2 Surface Discharge (Tracking) 4167.2.3 Degradation of Solid Dielectrics Caused by PB 4197.2.3.1 Inhibition of Partial Breakdown/Treeing in Solid Dielectrics 4207.2.4 Partial Breakdown Detection and Measurement 4227.2.4.1 Indirect Methods of PB Detection 4227.2.4.2 Direct Methods of PB Detection and Measurement 4237.3 Breakdown and Pre-breakdown Phenomena in Solid Dielectrics 4247.3.1 Intrinsic Breakdown Strength of Solid Dielectrics 4267.3.2 Thermal Breakdown 4297.3.3 Mechanism of Breakdown in Extremely Nonuniform Fields 4337.3.4 “Treeing” a Pre-breakdown Phenomenon in Polymeric Dielectrics 4347.3.4.1 Forms of Treeing Patterns 4347.3.4.2 Classification of Treeing Process 4347.3.5 Requirement of Time for Breakdown 4377.3.6 Estimation of Life Expectancy Characteristics 4407.3.7 Practical Breakdown Strength and Electric Stress in Service of Solid Dielectrics 4437.4 Development and Application of Solid Dielectric Line Insulators in High Voltage Power System 4447.4.1 Polymeric, also known as Composite Dielectric Insulators 4457.4.2 Design and Construction of Polymeric Insulators 4467.4.2.1 The Core or the Rod 4467.4.2.2 Metallic End Fittings 4467.4.2.3 The Weather Sheds 4477.4.3 Hollow Core Polymer Insulators 4497.4.4 Properties of Silicone Rubber and Fiber-Glass Reinforced Polymers 4507.4.4.1 Hydrophobicity 4507.4.5 Electrical Properties and Specified Tests 4527.4.5.1 Water Diffusion Test 4527.4.5.2 Water Immersion Test 4527.5 Condition Monitoring of Electrical Insulation 4537.5.1 Offline Single Measurement Techniques 4547.5.2 Online Continuous Measurement Techniques 4557.5.3 Construction of Large Rotating Electrical Machines 4567.5.3.1 Typical Nature of Insulation in Electrical Machines 4567.5.4 Partial Breakdown (PB) Monitoring Techniques Applied on Large Rotating Machines 4587.5.5 PB Measurements with VHF and UHF Sensors/Couplers 4607.5.5.1 Capacitive PB Couplers 4617.5.5.2 Inductive PB Couplers 4617.5.5.3 Electro-Magnetic (EM) PB Couplers 462References 464Index 469