This part of IEC 62271 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. 
NOTE While this technical report mainly addresses circuit-breakers, some clauses (e.g. Clause 5) apply to 
switchgear and controlgear. 
This technical report addresses utility, consultant and industrial engineers who specify and 
apply high-voltage circuit-breakers, circuit-breaker development engineers, engineers in 
testing stations, and engineers who participate in standardization. It is intended to provide 
background information concerning the facts and figures in the standards and provide a basis 
for specification for high-voltage circuit-breakers. Thus, its scope will cover the explanation, 
interpretation and application of IEC 62271-100 and IEC 62271-1 as well as related standards 
and technical reports with respect to high-voltage circuit-breakers. 
Rules for circuit-breakers with intentional non-simultaneity between the poles are covered by 
IEC 62271-302. 
This technical report does not cover circuit-breakers intended for use on motive power units of 
electrical traction equipment; these are covered by the IEC 60077 series. 
Generator circuit-breakers installed between generator and step-up transformer are not within 
the scope of this technical report. 
This technical report does not cover self-tripping circuit-breakers with mechanical tripping 
devices or devices which cannot be made inoperative. 
Disconnecting circuit-breakers are covered by IEC 62271-108. 
By-pass switches in parallel with line series capacitors and their protective equipment are not 
within the scope of this technical report. These are covered by IEC 62271-109 and 
IEC 60143-2. 
In addition, special applications (among others parallel switching, delayed current zero 
crossings) are treated in annexes to this document. 
 dition 1.1 2018-08 CONSOLIDATED VERSION colour inside High-voltage switchgear and controlgear – Part 306: Guide to IEC 62271-100, IEC 62271-1 and other IEC standards related to alternating current circuit-breakers IEC TR 62271-306:2012-12+AMD1:2018-08 CSV(en) THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright ？ 2018 IEC, Geneva, Switzerland All rights reserved. Unless otherwise specified, no par