Thursday, July 23, 2020

Electrical Installation Calculations Fourth Edition by Mark Coates and Brian Jenkins

 Download Electrical Installation Calculations Fourth Edition by Mark Coates and Brian Jenkins

Contents of Electrical Installation Calculations

1 Calculation of the cross-sectional areas of circuit live conductors
2 Calculation of voltage drop under normal load conditions
3 Calculation of earth fault loop impedance
4 Calculations concerning protective conductor cross-sectional area
5 Calculations related to short circuit conditions
6 Combined examples

Preface of Electrical Installation Calculations

The publication of BS 7671 and its predecessors, the 15th and 16th Editions of the IEE Wiring Regulations, led to a number of guides and handbooks being published by organizations involved in
the electrical contracting industry. These included the publication, by the Institution of Engineering
and Technology, of an On-site Guide and a number of Guidance Notes as well as several books by
independent authors and a considerable number of articles and papers in the technical press. It also
led to numerous instructional courses, seminars and conferences.
It was thought that there was little else one could write about concerning the Wiring Regulations,
but after talking to a number of engineers in the electrical installation contracting industry, Brian
Jenkins gained the strong impression that there was one need that had not really been satisfied. The
need was for a book that made considerable use of worked examples with the absolute minimum
discussion of the associated theoretical aspects. In other words, a book which used such examples to
show how one carried out the calculations involved in circuit design for compliance with BS 7671.
Whilst Brian designed the book to be primarily of interest and help to those in the smaller
companies in the electrical installation contracting industry, we believe the student and the plant
engineer will also find it of interest.
BS 7671 offers certain options. For example, when calculating voltage drop either an approximate
method or a more accurate one can be used and we have attempted to show where the latter could
be used to advantage. This, we believe, will make the book of interest to a wider circle.
BS 7671 does not refer to ‘touch voltages’ as such, these being the ‘voltages between simultaneously
accessible exposed and extraneous conductive parts’ that may lead to a risk of electric shock in the
event of an earth fault. It had long been Brian’s opinion that a fuller understanding of the touch
voltage concept would assist many in the electrical contracting industry to more fully understand the
requirements for automatic disconnection. For this reason we hope that the Appendix will prove to
be of interest.
Since the First Edition of this book there have been a number of amendments to the Requirement
for Electrical Installations. Some of the changes introduced by the amendments affect the examples
given in this book. The most important changes have been the change to the nominal voltage
from 240/415 V to 230/400 V, the change to the assumed temperature of conductors under fault
conditions and the inclusion of current-carrying capacities for buried cables. New work has also
been done to clarify the effectiveness of supplementary circuit protective conductors connected in
parallel with the armour of SWA cables. This Fourth Edition is intended to keep Electrical Installation Calculations up to date with the latest version of BS 7671. Examples using semi-enclosed fuses have, mainly for legacy, been retained and updated to BS 7671: 2008; although it is recognized that these devices would not generally be used for new installations, the examples present the reader with the
rudiments of the principles of calculations.
There is one final point which needs to be made in this Preface. Examination of some of the
answers may suggest to the reader that there is a high intrinsic degree of accuracy in installation
design calculations. This obviously cannot be true because, for example, estimated circuit lengths
will be rather approximate.
Many of the answers have been given to a greater number of significant figures than is necessary
in practice merely to assist the reader should he, or she, wish to check through the examples.

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