This International Standard is applicable to a.c. circuit-breakers designed for indoor or outdoor installation and for operation at frequencies of 50 Hz and 60 Hz on systems having voltages above 1 000 V. It is only applicable to three-pole circuit-breakers for use in three-phase systems and single-pole circuit-breakers for use in single-phase systems. Two-pole circuit-breakers for use in single-phase systems and application at frequencies lower than 50 Hz are subject to agreement between manufacturer and user. The contents of the corrigenda of October 2002 and April 2003 have been included in this copy. This consolidated version consists of the first edition (2001), its amendment 1 (2002) and its amendment 2 (2006). Therefore, no need to order amendments in addition to this publication.