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The death of Professor Arthur Wright in the summer of 1996 deprived me of a friend and a colleague whose judgement and experience shaped this book. I pay tribute to his contributions to protection and electrical engineering education. In the five years since the first edition appeared, many developments have taken place and it is now necessary to update the book. The use of digital communications and advanced signal processing techniques is now widespread and several fully numeric relays are available from manu facturers. Two new Chapters 13 and 14 have been added to introduce readers to these concepts and associated techniques. Artificial intelligence is making its impact in all engineering applications and power system protection is no exception. Expert systems, fuzzy logic, artificial neural networks, adaptive and integrated protection, synchronized measurements using the global positioning system, genetic algorithms, flexible a.c. transmission systems, are some of the techniques considered in connection with protection. Although many of these techniques have not yet found major application in protection, it is nevertheless essential for the educated protection engineer to have a basic understanding of the underlying principles and methodology so that he, or she, can evaluate their suitability for new relaying problems and applications. Chapter 15 was therefore added to guide readers through this developing area. I have also added some new material in other chapters to reflect changes over the past years.
List of contents
1 Fuses.- 2 Current transformers.- 3 Voltage transformers.- 4 Overcurrent and earth fault protection.- 5 Current-differential protective schemes.- 6 The protection of transformers.- 7 The protection of rotating machines.- 8 The protection of busbars.- 9 The protection of overhead lines and cables by current-differential schemes.- 10 Interlock and phase-comparison schemes for the protection of overhead lines.- 11 Distance-type protective schemes for overhead lines and cables.- 12 Ultra-high-speed schemes for the protection of long transmission lines.- 13 Digital communications.- 14 Digital signal processing (DSP) and protection.- 15 New relaying concepts.- Appendix A The testing and application of power-system protective equipment.- A.1 Performance requirements.- A.2 Testing of protective devices and equipment.- A.2.1 Fuselinks.- A.2.2 Current and voltage transformers.- A.2.3 The testing of relays.- A.2.4 The testing of protective schemes.- A.3 Automatic testing of relays and protective schemes.- References.- Appendix B Percentage and per-unit quantities.- Appendix C Transformations of three-phase quantities.- C.1 Voltage, current and impedance transformation.- C.2 Transformation into symmetrical components.- C.3 Other transformations.- References.- Appendix D The determination of power-system behavior using symmetrical components.- D.1 Sequence impedances.- D.1.1 Three-phase synchronous machines.- D.1.2 Transformers.- D.1.3 Overhead lines and cables.- D.1.4 The effects of physical asymmetry.- D.2 Sequence networks.- D.2.1 Earthing of neutral points.- D.2.2 Transformer connections.- D.3 The interconnection of sequence networks.- D.3.1 Balanced three-phase normal or fault conditions.- D.3.2 Conditions when a phase-to-phase fault is present.- D.3.3 Conditions when a singlephase to earth fault is present.- D.3.4 Impedances used in sequence networks.- D.4 Numerical example.- D.4.1 Short-circuit between phases 'b' and 'c' and earth.- D.4.2 Short-circuit between phase 'a' and earth.- Reference.- Concluding remarks.
