This book focuses on worked examples and keeps associated theoretical aspects to a minimum, furnishing the reader with the knowledge to carry out the necessary checks to electrical cable sizing software programmes. The book covers cross-sectional areas of circuit live conductors, voltage drop under normal load conditions, and earth fault loop impendances. It also has chapters on protective conductor cross-sectional areas and short circuit conditions. The final chapter combines all the calculations of the previous chapters to enable the reader to achieve the complete design of a circuit. This fourth edition includes important changes that take into account the 2008 updates to the BSI wiring regulations. It will be the first book on electrical installation calculations specifically, to incorporate these modifications. Fully revised to reflect the changes in the 17 th edition of the wiring regulations (published June 2008), including updated information on 230 volt references Includes new sections on buried cables that take into account soil thermal conductivity, trenches and grouping, allowing readers to carry out accurate cables sizing Supplies information and examples of steel wired armour cables, also new to this edition

Author Biography

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

Table of Contents

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