IEC 62271-105:2012 applies to three-pole units for public and industrial distribution systems which are functional assemblies of switches including switch-disconnectors and current-limiting fuses designed so as to be capable of - breaking, at the rated recovery voltage, any current up to and including the rated short-circuit breaking current; - making, at the rated voltage, circuits to which the rated short-circuit breaking current applies. It does not apply to fuse-circuit-breakers, fuse-contactors, combinations for motor-circuits or to combinations incorporating single capacitor bank switches. This second edition cancels and replaces the first edition of IEC 62271-105, published in 2002, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - implementation of figures at the place where they are cited first; - renumbering of tables; - addition of some of the proposals from IEC paper 17A/852/INF; - addition of missing subclauses of IEC 62271-1; - implementation of 6.105 "Extension of validity of type tests" and consequently removing of the relevant parts in the different existing clauses; - change of 7th paragraph of 6.101.4 as there is now a definition of NSDD given in 3.7.4 of IEC 62271-1:2007. Harmonization with IEC 62271-107; - some referenced clauses in other standards like IEC 60282-1 were changed and therefore changed the editions under 1.2 to the ones referred to; - addition of a new Annex C defining tolerances. This publication is to be read in conjunction with IEC 62271-1:2007.