Electrical Installation Calculations : For Compliance with BS 7671:2008 (Paperback, 4 ed)

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.