Electrical Installation Calculations: For Compliance with BS 7671:2008

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 17th edition of the wiring regulations (published June 2008), including updated information on 230 volt referencesIncludes new sections on buried cables that take into account soil thermal conductivity, trenches and grouping, allowing readers to carry out accurate cables sizingSupplies information and examples of steel wired armour cables, also new to this edition

Spis treści:
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 temperature s
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 the protective device is an mcb
Calculations when the protective device is an rccb
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