New Standard from Last Update.

NATIONAL FOREWORD

This Indian Standard (Part 1) (First revision) which is identical with IEC 60865-1 : 2011 ‘Shortcircuit currents — Calculation of effects — Part 1: Definitions and calculation methods’ issued by the International Electrotechnical Commission (IEC) was adopted by the Bureau of Indian Standards on recommendation of the Electrical Installations Sectional Committee and approval of the Electrotechnical Division Council.

IS 13235 was first published in 1991 and was based on IEC 60865 : 1986 ‘Calculation of effects of short–circuit currents’. IEC 60865:1986 has been revised and replaced by IEC 60865-1:2011 and IEC 60865-2:2015.

This standard was originally published in 1991 and was identical with IEC 60685 : 1986 ‘Calculation of effects of short-circuit currents’. The first revision of this standard has been undertaken to align it with the latest version of IEC 60685-1 : 2011.

The major changes in this revision are as follows:

a) The determinations for automatic reclosure together with rigid conductors have been revised.

b) The influence of mid-span droppers to the span has been included.

c) For vertical cable-connection the displacement and the tensile force onto the lower fixing point may now be calculated.

d) Additional recommendations for foundation loads due to tensile forces have been added.

e) The subclause for determination of the thermal equivalent short-circuits current has been deleted [ it is now part of IS 13234 (Part 1) ].

f) The regulations for thermal effects of electrical equipment have been deleted.

g) The standard has been reorganized and some of the symbols have been changed to follow the conceptual characteristic of Indian Standards.

This Indian standard is published in two parts. The other part in this series is:

Part 2 Examples of calculation

The text of IEC Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain terminologies and conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker, while in Indian Standards, the current practice is to use a point (.) as the decimal marker.