Electrical Installation Calculations: For Compliance with BS 7671:2008

Manual calculations are still extensively used and in particular are necessary for checking and verifying various software calculation design packages. It is highly recommended that users of such software familiarise themselves with the rudiments of these calculations prior to using the software packages. This essential book fills the gap between software and manual calculations. It provides the reader with all the necessary tools to enable accurate calculations of circuit designs. Rather than complex equations, this book uses extensive worked examples to make understanding the calculations simpler. The focus on worked examples furnishes the reader with the knowledge to carry out the necessary checks to electrical cable sizing software programmes. Other key features include: Updated information on 230 volt references and voltage drop under normal load conditions New sections on buried cables that take into account soil thermal conductivity, trenches and grouping, allowing readers to carry out accurate cables sizing Information and examples of steel wired armour cables, new to this edition. This includes sufficiency during short circuits and, for cables with externally run CPCs, gives unique fault conditions. Covers calculations of cross-sectional areas of circuit live conductors Earth fault loop impedances Protective conductor cross-sectional areas and short circuit conditions Short circuit protection. The last chapter combines all of the calculations of the previous chapters to enable the reader to complete an accurate design of an installation circuit under all conditions. A unique tool for detailed electrical installation trade, Electrical Installation Calculations, Fourth Edition is invaluable to electricians, electrical designers, installers, technicians, contractors, and plant engineers. Senior electrical engineering students and technical colleges, junior engineers, and contracts managers will also find this text useful.

Table of Contents:
About the authors vii Preface ix Acknowledgements xi Symbols xiii Definitions xv 1 Calculation of the cross-sectional areas of circuit live conductors 1 General circuits 4 Circuits in thermally insulating walls 5 Circuits totally surrounded by thermally insulating material 6 Circuits in varying external influences and installation conditions 6 Circuits in ventilated trenches 8 Circuits using mineral-insulated cables 9 Circuits on perforated metal cable trays 10 Circuits in enclosed trenches 11 Circuits buried in the ground 14 Grouped circuits not liable to simultaneous overload 18 Circuits in low ambient temperatures 24 Grouped ring circuits 26 Motor circuits subject to frequent stopping and starting 27 Circuits for star-delta starting of motors 29 Change of parameters of already installed circuits 30 Admixtures of cable sizes in enclosures 33 Grouping of cables having different insulation 39 2 Calculation of voltage drop under normal load conditions 40 The simple approach 40 The more accurate approach taking account of conductor operating temperature 43 The more accurate approach taking account of load power factor 55 The more accurate approach taking account of both conductor operating temperature and load power factor 58 Voltage drop in ring circuits 59 Voltage drop in ELV circuits 62 3 Calculation of earth fault loop impedance 65 The simple approach 70 The more accurate approach taking account of conductor temperature 75 Calculations taking account of transformer impedance 81 Calculations concerning circuits fed from sub-distribution boards 82 Calculations where conduit or trunking is used as the protective conductor 87 Calculations where cable armouring is used as the protective conductor 94 4 Calculations concerning protective conductor cross-sectional area 101 Calculations when the protective device is a fuse 104 Calculations when an external cpc is in parallel with the armour 111 Calculations when the protective device is an mcb 113 Calculations when the protective device is an RCD or RCBO 119 5 Calculations related to short circuit conditions 126 a.c. single-phase circuits 127 The more rigorous method for a.c. single-phase circuits 135 a.c. three-phase circuits 141 6 Combined examples 153 Appendix: The touch voltage concept 175 Index 189

About the Author :
Professor Mark Coates, ERA Technology Ltd, Surrey, UK Professor Coates is an internationally renowned expert on current ratings for high and low voltage cable systems. He joined ERA Technology in 1983 and is currently Head of Cables at ERA's Engineering Consultancy business. His areas of expertise include measurement of the thermal properties of cable materials, calculation of heat flow through complex thermal paths, MV partial discharge, breakdown testing and life prediction using statistical analysis. He has been one of the leading contributors to the work of IEC Technical Committee 20 (Electric Cables). Professor Coates is an active member of the IEE/BSI Committee concerned with electrical installations, BS7671. Before joining ERA, he spent several years as a plant engineer in the chemical and textile industry. Mr Brian D. Jenkins, (deceased), formerly British Standards Institution

Review :
"This essential book fills the gap between software and manual calculations. It provides the reader with all the necessary tools to enable accurate calculations of circuit designs. Rather than complex equations, this book uses extensive worked examples to make understanding the calculations simpler." (Broadcastnewsroom, 20 October 2010).