DESIGN AND APPLICATION OF LV SWITCHGEAR TO MEET THE LATEST REVISIONS OF INTERNATIONAL STANDARDS.

Over the last few years there have been fundamental changes to the specifications for lv switchgear. These have chiefly been brought about by the introduction of IEC requirements. Today all lv circuit-breakers whether conventional airbreak or molded case should be designed, manufactured and tested to IEC 157-1, 1973. The BS4752, 1977 is identical to IEC 157-1, 1973. IEC 157-1 is being completely revised since there are several aspects of the existing issue which are considered unsatisfactory. However, this revision is not likely to be formally issued for another 1 one-half -2 years, and the related British Standard BS4752 another year after that. Two aspects considered unsatisfactory in the existing specification and which are being rectified in the revision are outlined such that the user can be familiarized prior to the revision being formally issued. They are short circuit categories and method of short circuit testing.