Contents
- Preface ………………………………………………………………………………………………………………. 5
- Introduction ……………………………………………………………………………………………………….. 7
- Definitions and general approach………………………………………………………………………….. 8
- Instantaneous or Definite Time Overcurrent Protection………………………………………… 14
- Inverse Time Overcurrent Protection …………………………………………………………………… 15
- Distance protection……………………………………………………………………………………………. 17
- Transformer Differential protection …………………………………………………………………….. 19
- Line Differential protection …………………………………………………………………………………. 21
- Generator Differential protection ……………………………………………………………………….. 24
- Low Impedance Busbar Protection ………………………………………………………………………. 26
APPENDIX 1 ………………………………………………………………………………………………………….. 28
Criteria for CT verification during internal faults ……………………………………………………….. 28
APPENDIX 2 ………………………………………………………………………………………………………….. 32
Dimensioning of Current Transformers (CT) for Application in Protection ……………………. 32
APPENDIX 3 ………………………………………………………………………………………………………….. 47
Typical X/R values …………………………………………………………………………………………………. 47
APPENDIX 4 ………………………………………………………………………………………………………….. 49
Criteria for CT calculation in High Impedance Relays …………………………………………………. 49
APPENDIX 5 ………………………………………………………………………………………………………….. 54
Calculation Examples …………………………………………………………………………………………….. 54
APPENDIX 6 ………………………………………………………………………………………………………….. 57
Importance of having similar CT characteristics in a Generator Differential protection …. 57
APPENDIX 7 ………………………………………………………………………………………………………….. 61
CT Equivalences between IEC and ANSI Standards ……………………………………………………. 61
APPENDIX 8 ………………………………………………………………………………………………………….. 63
Conversion in class TPX or equivalent 5P …………………………………………………………………. 63
APPENDIX 9 ………………………………………………………………………………………………………….. 64
Questions and answers ………………………………………………………………………………………….. 64
APPENDIX 10 ………………………………………………………………………………………………………… 83
Permeability and Saturation …………………………………………………………………………………… 83
APPENDIX 11 ………………………………………………………………………………………………………… 92
Terms and Definitions ……………………………………………………………………………………………. 92
References ………………………………………………………………………………………………………………. 96