http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Non-destructive diagnostic of high voltage electrical systems
theoretical analysis and practical applications
Preface xiii List of Figures xv List of Tables xxv List of Abbreviations xxvii 1 Introduction 1 2 General View on Diagnostics of Electrical Machines 5 2.1 Diagnosed Object 5 2.2 Online and Offline Diagnostic 7 2.2.1 Offline diagnostic 8 2.2.2 Online diagnostic 9 2.3 Forecast of the Condition of the Diagnosed Device 10 References 12 3 Diagnostics of Mechanical Parts of HV Machines 13 3.1 Measuring Machine Vibration 13 3.1.1 Types of vibrations and vibrodiagnostic quantities 13 3.1.2 Vibrometer sensors 15 3.1.2.1 Deflection sensors 17 3.1.2.2 Speed sensors 18 3.1.2.3 Acceleration sensors 19 3.1.3 Analysis of vibrometric signals 24 3.1.3.1 Analysis of vibrometric signals in the time domain 24 3.1.3.2 Analysis of vibrometric signals in the frequency domain 25 3.2 Torsional Oscillation of Shafts 33 3.2.1 Causes of shaft torsional oscillation 33 3.2.2 Measurement of shaft torsional oscillation 35 3.3 Measurement of Temperature Images of Electrical Machines 37 3.3.1 Contact temperature sensors 39 3.3.2 Non-contact temperature sensors 45 References 46 Author Queries 48 4 Insulation Systems of HV Electric Machines 49 4.1 Electrical Properties of Insulators 49 4.1.1 Electrical strength of insulators 49 4.1.1.1 Electrical strength of gaseous insulators 49 4.1.1.2 Electrical strength of liquid insulators 54 4.1.1.3 Electrical strength of solid insulators 57 4.1.2 Electrical conductivity of insulators 59 4.1.2.1 Electrical conductivity of gaseous insulators 60 4.1.2.2 Electrical conductivity of liquid insulators 60 4.1.2.3 Electrical conductivity of solid insulators 63 4.1.3 Polarization of insulators 64 4.1.4 Dielectric losses in insulators 66 4.1.4.1 Dielectric losses in gaseous insulators 67 4.1.4.2 Dielectric losses in liquid insulators 68 4.1.4.3 Dielectric losses in solid insulators 68 4.2 Types of Insulators 69 4.2.1 Gaseous insulators 70 4.2.2 Liquid insulators 71 4.2.3 Solid insulators 74 4.3 Electrical Stress on Insulators 76 4.3.1 Stress on plate insulators 77 4.3.2 Stress on cylindrical insulators 78 4.4 Degradation of Isolators 80 4.4.1 Mechanical aging 81 4.4.2 Thermal aging 81 4.4.3 Electrical aging 84 4.4.4 Combined aging 86 References 89 5 Measurement of Properties of Insulation Systems of HV Electrical Machines 91 5.1 Measurement of Insulation Current and Resistance 91 5.2 Measurement of Capacity and Loss Factor 93 5.2.1 Measurement of capacity and loss factor by the HV Schering bridge 95 5.2.2 Measurement of capacitance and loss factor of HV impedance meters 97 5.2.3 Measurement of frequency dependence of capacity and loss factor 102 5.3 Measurement of Dielectric Absorption of Insulation Systems 104 References 107 6 Partial Discharges in Insulating Systems of HV Electric Machines 109 6.1 Formation and Types of Partial Discharges 109 6.2 Partial Discharge Parameters 112 6.3 Partial Discharge Models 117 6.3.1 Model of external and surface partial discharges 117 6.3.2 Gemant⁰́₃Philippoff model of internal partial discharges 118 6.3.3 B©œnings model of internal partial discharges 121 6.4 Effect of Partial Discharges on the Insulation Systems of HV Machines 123 6.4.1 Electro-erosive effects of partial discharges 124 6.4.2 Chemical effects of partial discharges 124 6.4.3 Thermal effects of partial discharges 125 References 125 7 Measurement and Detection of Partial Discharges 129 7.1 Electrical Methods Measurement and Detection of Partial Discharges 129 7.1.1 Properties of partial discharge current pulses 129 7.1.2 Galvanic methods for measuring partial discharges 131 7.1.2.1 Coupling capacitors 134 7.1.2.2 Coupling impedance 134 7.1.3 Measurement of partial discharges 138 7.1.3.1 Measurement of partial discharges with oscilloscope 139 7.1.3.2 Measurement of partial discharges by a peak detector 139 7.1.3.3 Partial discharge meters with direct signal digitization 142 7.1.4 Charge calibration 149 7.1.5 Measurement of partial discharges by current transformers 151 7.1.6 Measurement of partial discharges by inductive probes 153 7.1.7 Measurement of partial discharges by capacitive probes 156 7.2 Non-electrical Methods for the Detection of Partial Discharges 159 7.2.1 Ultrasonic detection of partial discharges 159 7.2.2 High-frequency detection of partial discharges 162 7.2.3 Optical partial discharges detection 166 7.2.4 Chemical detection of partial discharges 167 References 170 8 Voltage Tests of HV Electric Machines 173 8.1 DC Voltage Tests 173 8.2 AC Voltage Tests 173 8.3 Voltage Tests by Long-term Induced Voltage 174 8.4 Impulse Voltage Tests 174 8.4.1 Course of impulse voltage tests 175 8.4.2 Test pulses 175 8.4.3 Generation of test voltage pulses 178 8.4.3.1 Single-stage voltage shock generators 178 8.4.3.2 Multi-stage voltage shock generators 179 8.4.4 Voltage level impulse tests 181 8.4.4.1 Tests with a constant number of voltage levels 182 8.4.4.2 Up⁰́₃down tests 182 8.4.4.3 Phased stress tests 184 8.4.4.4 Statistical methods for the evaluation of level tests 186 8.5 Shock Wave Tests 189 References 191 9 Diagnostics of Power Transformers 193 9.1 Types of Power Transformers 193 9.2 Properties of Transformers 194 9.3 Diagnostics of Electrical Properties of Power Transformers 197 9.3.1 Measurement of active winding resistance 198 9.3.2 Checking the sequence and rotation of the phases 200 9.3.3 Measurement of transmission, voltage, and no-load losses 202 9.3.4 Measurement of short-circuit voltages and losses 204 9.3.5 Measuring the efficiency of transformers 205 9.3.6 Measurement of insulation resistance, polarization index, and transformer time constant 210 9.3.7 Measurement of loss factor and winding capacity 211 9.3.8 Winding fault detection 215 9.4 Diagnostics of Transformer Oil Properties 220 9.4.1 Measurement of electrical properties of transformer oils 221 9.4.1.1 Measurement of breakdown voltage at mains frequency 221 9.4.1.2 Measurement of relative permittivity and loss factor 222 9.4.1.3 Measurement of internal resistivity of transformer oils 224 9.4.2 Measurement of physical properties of transformer oils 225 9.4.2.1 Transformer oil color measurement 225 9.4.2.2 Transformer oil density measurement 225 9.4.2.3 Measuring the viscosity of transformer oils 227 9.4.2.4 Measurement of flash and combustion temperatures 228 9.4.2.5 Freezing temperature measurement 228 9.4.3 Measurement of chemical properties of transformer oils 229 9.4.3.1 Water content measurement 229 9.4.3.2 Oil acid measurement 231 9.4.3.3 Measurement of the presence of sulfur 232 9.4.3.4 Content of polycyclic aromatics and polychlorinated biphenyls 232 9.4.3.5 Gas content measurement 232 References 233 10 Diagnostic of Rotary HV Electrical Machines 237 10.1 Types of HV Rotary Electrical Machines 237 10.2 Properties of HV Rotary Electrical Machines 239 10.3 Diagnostics of HV Rotary Electrical Machines 242 10.3.1 Offline diagnostic of HV rotary electrical machines 242 10.3.2 Online diagnostic of HV rotary electrical machines 243 10.3.2.1 Ozone detection measurement 243 10.3.2.2 Measurement of hydrogen purity in cooling systems of electrical machines 243 10.3.2.3 Frequency analysis of currents and scattering magnetic fields 245 10.3.2.4 Measurement of machine noise 248 10.3.2.5 Online monitoring of partial discharges 251 10.3.3 Shaft voltages and currents 251 10.3.3.1 Generation of shaft voltages and currents 251 10.3.3.2 Measurement of shaft voltages and currents 252 10.3.3.3 Means of suppressing shaft voltages and currents 255 References 257 11 Diagnostics of HV Power Cables 259 11.1 Types of MV Power Cables 259 11.2 Properties of High-voltage Power Cables 261 11.3 Measurement of Properties of HV Power Cables 265 11.3.1 Measuring the resistance of cables 265 11.3.2 Measuring the through resistance of cables 266 11.3.3 Measurement of cable leakage resistances 267 11.3.4 Measurement of capacity and loss factor of cables 269 11.3.5 Measurement of partial discharges in cables 273 References 276 12 Diagnostics of Insulators, Surge Arresters, and Circuit Breakers 279 12.1 HV Insulators 279 12.1.1 Parameters of HV insulators 280 12.1.2 Voltage tests of insulators 281 12.1.2.1 Dry stress tests 282 12.1.2.2 Wet stress tests 283 12.2 Preload Arresters 285 12.2.1 Types of surge arresters 285 12.2.1.1 Air spark gap 286 12.2.1.2 Blow arrester 286 12.2.1.3 Valve lightning arrester 287 12.2.1.4 Non-sparking preload limiters 288 12.2.2 Parameters of preload limiters 289 12.2.3 Voltage tests of voltage arresters 289 12.2.3.1 Ignition voltage tests 290 12.2.3.2 Residual voltage measurement 290 12.2.3.3 Current pulse endurance test 291 12.2.3.4 Operational functionality tests 291 12.3 Power Switches and Disconnectors 292 12.3.1 Diagnostic methods for circuit breakers 292 References 293 List of symbols 295 List of Constants and Quantities 297 List of Standards 299 Index 303 About the Author 307.
In 1971, Josef Vedral graduated from the Czech Technical University in Prague, Faculty of Electrical Engineering in the field of measuring technology. In 1976 he completed his doctoral studies at the Department of Measurement of the Czech Technical University in Prague in the field of measuring instrumentation. In recent years, he has been engaged in condition monitoring of HV electric machines. Between 2012 and 2020 he was the head of two projects of the Technology Agency of the Czech Republic projects "Intelligent measuring diagnostic system for estimating the operating condition of high-voltage electric rotary and non-rotating machines" and the related project "Compact diagnostic system for monitoring the condition of high-voltage electric machines using DC and low-frequency alternating test voltage". He is the author of 82 scientific articles in international journals, 12 Czech patents, 12 university textbooks in Czech and 2 textbooks in English.
Power, Energy and Industry Applications.
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