Voltage quality in electrical power systems

Problems of voltage quality and their solutions are becoming increasingly important with the growth in power electronics and the high sensitivity of electronic equipment. Translated and updated from the German original published by VDE-Verlag, this book successfully details the theoretical and practical background to low voltage conducted disturbances including harmonics, voltage fluctuation/flicker and asymmetrical voltages.

Each chapter is illustrated with practical examples and exercises based on the authors' experience of application problems, including measurement, assessment and remedial measures. The book is set in the context of European standards.

This book will be of interest to electrical engineers in industry, utilities and universities, as well as companies interested in planning, operating and designing power system equipment.

Foreword	p. ix
1 Introduction	p. 1
1.1 Electromagnetic compatibility in electrical supply systems	p. 1
1.2 Classification of system perturbations	p. 4
1.3 EU directives, VDE specifications and standards	p. 6
1.4 Basic mathematical principles	p. 10
1.4.1 Complex calculations, vectors and phasor diagrams	p. 10
1.4.2 Fourier analysis and synthesis	p. 12
1.4.3 Symmetrical components	p. 17
1.4.4 Power considerations	p. 21
1.4.5 Series and parallel resonant circuits	p. 23
1.5 System conditions	p. 27
1.5.1 Voltage levels and impedances	p. 27
1.5.2 Features of the voltage in power systems	p. 29
1.5.3 Impedances of equipment	p. 31
1.5.4 Characteristics of typical equipment	p. 36
1.6 Calculation examples	p. 39
1.6.1 Graphical determination of symmetrical components	p. 39
1.6.2 Arithmetical determination of symmetrical components	p. 41
1.6.3 Calculation of equipment	p. 41
1.7 References	p. 43
2 Harmonics and interharmonics	p. 45
2.1 Occurrence and causes	p. 45
2.1.1 General	p. 45
2.1.2 Occurrence due to network equipment	p. 45
2.1.3 Occurrence due to power electronics equipment	p. 48
2.1.3.1 Basic principles	p. 48
2.1.3.2 Full-wave rectifier with capacitor smoothing	p. 49
2.1.3.3 Three-phase bridge circuit	p. 51
2.1.3.4 Converters	p. 57
2.1.4 Occurrence due to random consumer behaviours	p. 60
2.1.5 Telecontrol signals	p. 62
2.2 Description and calculations	p. 64
2.2.1 Characteristics and parameters	p. 64
2.3 Harmonics and interharmonics in networks	p. 66
2.3.1 Calculation of networks and equipment	p. 66
2.3.2 Modelling of equipment	p. 67
2.3.3 Resonances in electrical networks	p. 68
2.4 Effects of harmonics and interharmonics	p. 72
2.4.1 General	p. 72
2.4.2 High-energy equipment	p. 73
2.4.3 Network operation	p. 76
2.4.4 Electronic equipment	p. 77
2.4.5 Protection, measuring and automation equipment	p. 77
2.4.6 Loads and consumers	p. 78
2.4.7 Assessment of harmonics	p. 81
2.5 Standardisation	p. 84
2.5.1 General	p. 84
2.5.2 Emitted interference	p. 85
2.5.3 Compatibility levels	p. 87
2.5.4 Interference immunity levels	p. 90
2.6 Examples of measurement and calculation	p. 90
2.6.1 Harmonic resonance due to reactive power compensation	p. 90
2.6.2 Assessment of a harmonic generator	p. 93
2.6.3 Impedance calculation in a medium voltage network	p. 95
2.6.4 Typical harmonic spectra of low voltage consumers	p. 97
2.7 References	p. 100
3 Voltage fluctuations and flicker	p. 103
3.1 Definitions	p. 103
3.2 Occurrence and causes	p. 104
3.2.1 Voltage fluctuations	p. 104
3.2.2 Flicker	p. 105
3.3 Flicker calculation in accordance with empirical formulae	p. 105
3.3.1 General	p. 105
3.3.2 Calculation of the voltage drop in general form	p. 106
3.3.3 A[subscript st]/P[subscript st] calculation	p. 110
3.4 Flicker calculation for random signals	p. 111
3.4.1 Mathematical description of the flicker algorithm	p. 111
3.4.2 The P[subscript st] disturbance assessment method	p. 114
3.5 Effects of voltage fluctuations	p. 115
3.6 Standardisation	p. 116
3.7 Examples of measurement and calculation	p. 118
3.7.1 Measurement of flicker in a low voltage system	p. 118
3.7.2 Calculation of an industrial system for resistance heating	p. 119
3.8 References	p. 122
4 Voltage unbalance	p. 123
4.1 Occurrence and causes	p. 123
4.2 Description of unbalances	p. 123
4.2.1 Simplified examination	p. 123
4.2.2 Symmetrical components	p. 124
4.3 Effects of voltage unbalance	p. 125
4.4 Standardisation	p. 125
4.5 Examples of measurement and calculation	p. 125
4.5.1 Measurement of unbalance in an industrial 20 kV system	p. 125
4.5.2 Determining the unbalance of an industrial system	p. 126
4.6 Reference	p. 127
5 Measurement and assessment of system perturbations	p. 129
5.1 General	p. 129
5.2 Sampling systems	p. 130
5.2.1 General characteristics	p. 130
5.2.2 Basic structure of a digital measuring instrument	p. 130
5.2.3 Transient recorders	p. 132
5.2.4 Harmonics analysers	p. 134
5.2.5 Flicker meter	p. 135
5.2.6 Combination instruments	p. 137
5.3 Measured value processing	p. 137
5.3.1 Statistical methods	p. 137
5.3.2 Measuring and evaluation methods	p. 141
5.4 Accuracy	p. 143
5.4.1 Algorithms and evaluation	p. 143
5.4.2 Instrument and isolating transformers, current clamp	p. 144
5.5 Use and connection of measuring instruments	p. 147
5.5.1 Low voltage system	p. 147
5.5.2 Medium and high voltage systems	p. 147
5.6 Standardisation	p. 150
5.7 Characteristics of measuring instruments	p. 150
5.8 Performance of measurements	p. 152
5.9 References	p. 153
6 Countermeasures	p. 155
6.1 Assignment of countermeasures	p. 155
6.2 Reduction of the emitted interference from consumers	p. 155
6.3 Consumer-related measures	p. 158
6.3.1 Filter circuits	p. 158
6.3.2 Dynamic reactive power compensation	p. 163
6.3.3 Symmetrical connections	p. 163
6.3.4 Active filters	p. 164
6.3.4.1 High-performance batteries	p. 167
6.3.4.2 Superconductive magnetic energy storage	p. 168
6.3.4.3 Gyrating mass flywheel	p. 170
6.3.4.4 Comparison of various energy storage devices	p. 172
6.4 Measures related to power systems	p. 172
6.4.1 Measures during network planning: system strengthening measures	p. 172
6.4.2 Measures with regard to system operation: short-circuit current limitation	p. 174
6.5 Cost analysis	p. 178
6.6 Example of an application: planning an active filter UPCS project	p. 179
6.6.1 Designing the UPCS	p. 179
6.6.1.1 Design of the UPCS to compensate for harmonics	p. 180
6.6.1.2 Design of the UPCS with regard to voltage sags and flicker	p. 186
6.6.2 Example of network planning, taking account of active system filters	p. 193
6.6.2.1 System connection variants of a large industrial customer	p. 195
6.6.2.2 Optimisation of the location of active filters	p. 203
6.6.3 Assessment of active network filters from the point of view of network planning	p. 204
6.7 References	p. 204
7 Notes on practical procedures	p. 207
7.1 Survey of voltage quality (harmonics) in medium voltage networks	p. 207
7.2 Connection of harmonics generators, high-load consumers	p. 209
7.3 Determining the reference values for planning calculations in a ring-cable network	p. 216
7.3.1 Measurements in a 35 kV ring-cable network	p. 216
7.4 Disturbance investigation	p. 218
7.4.1 Disturbance analysis harmonics in power station service network I	p. 218
7.4.2 Disturbance analysis (voltage increase) in power station service network II	p. 221
7.4.3 Network resonance in the low voltage network	p. 224
7.4.4 Reactive power compensation in a 500 V network	p. 227
7.5 References	p. 231
8 Appendix	p. 233
8.1 Formula symbols and indices	p. 233
8.1.1 Formula symbols	p. 233
8.1.2 Indices, subscript	p. 235
8.1.3 Indices, superscript	p. 236
Index	p. 239

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