• Book Name: Electrical Installation Calculations
• Author: Mark and Brain
• Pages: 214
• Size: 4 MB

About the authors: Mark Coates BEng collaborated with Brian in developing the First Edition and has since been responsible for revising the subsequent editions. He joined ERA Technology Ltd (now trading as Cobham Technical Services) in July 1983 and is currently a Cable Engineering Consultant. He gained a degree in Mechanical Engineering from Sheffield University (UK) in 1977 and he worked for a chemical and textile company until 1983. Since joining ERA, he has primarily worked on projects to determine cable current ratings both experimentally and by theoretical methods.

In addition to the usual cable rating problems, this work has included development of rating methods for mixed groups of cable, cables on winch drums and sub-sea umbilicals. Other projects have included assessments of new cable designs, the mechanical performance of cables and joints, failure analysis of LV, MV and HV transmission and distribution equipment, and life prediction tests for HV cables.

He is a member of the UK IEE/BSI Committee concerned with electrical installations, and attends BSI and IEC meetings. He is the convenor of IEC TC20 WG19, the specialist IEC working group responsible for maintaining and updating the International Standards on steady state, cyclic and short-circuit ratings of power cables. Brian Jenkins BSc, CEng, FIEE had many years’ industrial experience before working as a Principal Technical Officer at the British Standards Institution. He then joined the Institution of Electrical Engineers as a Senior Technical Officer. Brian passed away in 2007.

Electrical Installation Calculations by Mark and Brain

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.

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