IEC 62271-101:2012+A1:2017 mainly applies to a.c. circuit-breakers within the scope of IEC 62271-100. It provides the general rules for testing a.c. circuit-breakers, for making and breaking capacities over the range of test duties described in 6.102 to 6.111 of IEC 62271-100:2008, by synthetic methods. This second edition cancels and replaces the first edition published in 2007 and its Amendment 1 published in 2011. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the first edition:- addition of the new rated voltages of 1 100 kV and 1 200 kV;- revision of Annex F regarding circuit-breakers with opening resistors;- alignment with the second edition of IEC 62271-100:2008 and its Amendment 1 (2012).This publication is to be read in conjunction with IEC 62271-100:2008. This consolidated version consists of the second edition (2012) and its amendment 1 (2017). Therefore, no need to order amendment in addition to this publication.