Electrical Installation Calculations – for Compliance with BS 7671 – 2008 4e

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

About the Authors. Preface. Acknowledgements. Symbols. Definitions. 1 Calculation of the cross-sectional areas of circuit live conductors. General circuits. Circuits in thermally insulating walls. Circuits totally surrounded by thermally insulating material. Circuits in varying external influences and installation conditions. Circuits in ventilated trenches. Circuits using mineral-insulated cables. Circuits on perforated metal cable trays. Circuits in enclosed trenches. Circuits buried in the ground. Grouped circuits not liable to simultaneous overload. Circuits in low ambient temperatures. Grouped ring circuits. Motor circuits subject to frequent stopping and starting. Circuits for star-delta starting of motors. Change of parameters of already installed circuits. Admixtures of cable sizes in enclosures. Grouping of cables having different insulation. 2 Calculation of voltage drop under normal load conditions. The simple approach. The more accurate approach taking account of conductor operating temperature. The more accurate approach taking account of load power factor. The more accurate approach taking account of both conductor operating temperature and load power factor. Voltage drop in ring circuits. Voltage drop in ELV circuits. 3 Calculation of earth fault loop impedance. The simple approach. The more accurate approach taking account of conductor temperature. Calculations taking account of transformer impedance. Calculations concerning circuits fed from sub-distribution boards. Calculations where conduit or trunking is used as the protective conductor. Calculations where cable armouring is used as the protective conductor. 4 Calculations concerning protective conductor cross-sectional areas. Calculations when the protective device is a fuse. Calculations when an external cpc is in parallel with the armour. Calculations when the protective device is an mcb. Calculations when the protective device is an RCD or RCBO. 5 Calculations related to short circuit conditions. a. c. single-phase circuits. The more rigorous method for A.C. single-phase circuits. a.c. three-phase circuits. 6 Combined examples. Appendix The touch voltage concept. Index.