Contents. Preface. Chapter 2 Faults, types and effects The development of simple distribution systems Faults-types and their effects 7

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1 Practical Power System Protection for Engineers and Technicians Contents Preface ix Chapter 1 Need for protection Need for protective apparatus Basic requirements of protection Basic components of protection Summary 3 Chapter 2 Faults, types and effects The development of simple distribution systems Faults-types and their effects 7 Chapter 3 Simple calculation of short circuit currents Introduction Revision of basic formulae Calculation of short circuit MVA Useful formulae Cable information 26 Chapter 4 System Grounding Introduction Grounding devices Evaluation of grounding methods Effect of electric shock on human beings 35 Chapter 5 Fuses Historical Re-wireable type 39

2 5.3 Cartridge type Operating characteristics British standard 88: Energy let through Application of selection of fuses General rules of thumb Special types General I S -limiter 46 Chapter 6 Instrument transformers Purpose Basic theory of operation Voltage transformers Current transformers Application of current transformers Introducing relays Inverse definite minimum time lag (IDMTL) relay 79 Chapter 7 Circuit breakers Introduction Protective relay circuit breaker combination Purpose of circuit breakers (switchgear) Behavior under fault conditions Arc Types of circuit breakers Comparison of breaker types 97 Chapter 8 Tripping batteries Tripping batteries Construction of battery chargers Maintenance guide Trip circuit supervision Reasons why breakers and contactors fail to trip Capacity storage trip units 122

3 Chapter 9 Relays Introduction Principle of the construction and operation of the IDMTL relay Factors influencing choice of plug setting The new era in protection microprocessor vs electronic vs traditional Universal microprocessor overcurrent relay Technical features of a modern microprocessor relay Type testing of static relays The future of protection for distribution systems The era of the IED Substation automation Communication capability 167 Chapter 10 Co-ordination by time grading Introduction What is coordination? Over-current coordination Protection design parameters on medium and low voltage networks Sensitive ground fault protection 205 Chapter 11 Low voltage network Introduction Air circuit breakers Moulded case circuit breakers Application and selective co-ordination Ground leakage protection 223 Chapter 12 Mine underground distribution protection General Ground leakage protection Pilot wire monitor Ground fault lockout Neutral grounding resistor monitor (NERM) 235

4 Chapter 13 Principles of unit protection Protective relay systems Main or unit protection Back-up protection Methods of obtaining selectivity Differential protection Transformer differential protection Switchgear differential protection Feeder pilot-wire protection Time taken to clear faults Recommended unit protection systems Advantages of unit protection 253 Chapter 14 Feeder protection cable feeders and overhead lines Introduction Translay Solkor protection Distance protection 260 Chapter 15 Transformer protection Winding polarity Transformer connections Transformer magnetizing characteristics In-rush current Neutral grounding On-load tap changers Mismatch of current transformers Types of faults Differential protection Restricted ground fault HV overcurrent Protection by gas sensing and pressure detection Overloading 312 Chapter 16 Switchgear (busbar) protection Importance of busbars Busbar protection The requirements for good protection Busbar protection types 321

5 Chapter 17 Motor protection relays Introduction Stalling of motors Overcurrent/overload Undervoltage/overvoltage Underfrequency Pole slip/out of step Loss of excitation Inadvertant energization Overfluxing Stall protection/acceleration time Negative sequence events Derating factors Earth faults core balance, residual stabilizing factors Calculation of protective relay settings Example 361 Chapter 18 Generator protection Introduction Stator grounding and ground faults Overload protection Overcurrent protection Overvoltage protection Unbalanced loading Rotor faults Reverse power Loss of excitation Loss of synchronization Field suppression Industrial generator protection Numerical relays Parallel operation with grid 375 Chapter 19 Cables and protection Introduction Advantages of cables over overhead transmission lines Disadvantages of cables in power transmission Types of cables 380

6 19.5 Cable jointing (splicing) accessories Need for termination kits Types of failures Reasons for failure Short circuit protection of underground cables Cable protection applications Fault location Electrical tests for detection of cable faults Analysis of failures Documentation 408 Chapter 20 Management of Protection Management of protection Schedule A Schedule B Test sheets 417 Appendix A The Protection of Railway Traction Circuits 423 Appendix B Typical Cable Data Sheets 433 Appendix C Practical exercises on relay coordination 437 Appendix D SIPROTEC4 7SA6 Distance Protection relay 443 Appendix E SIPROTEC4 7SJ64 Feeder Management Relay 453 Appendix F SIPROTEC4 7SD61 Line Differential Relay 463

7 Appendix G SIPROTEC4 7SS60 Feeder Management Relay 473 Appendix H SIPROTEC4 7UT6 Transformer Differential Relay 479 Appendix I Arc Sensors 487 Appendix J Integral Digital Protection Devices 495