IEC 62271-100:2021 is applicable to three-phase AC circuit-breakers designed for indoor or outdoor installation and for operation at frequencies of 50 Hz and/or 60 Hz on systems having voltages above 1 000 V. This document includes only direct testing methods for making-breaking tests. For synthetic testing methods refer to IEC 62271-101. This third edition cancels and replaces the second edition published in 2008, Amendment 1:2012 and Amendment 2:2017. This edition constitutes a technical revision. The main changes with respect to the previous edition are listed below: – the document has been updated to IEC 62271-1:2017; – Amendments 1 and 2 have been included; – the definitions have been updated, terms not used have been removed; – Subclauses 7.102 through 7.108 have been restructured.