IEC 62271-105:2021 applies to three-pole units for public and industrial distribution systems which are functional assemblies of switches composed of switches or switch-disconnectors and current-limiting fuses designed so as to be capable of:
- breaking, at the rated 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.
This third edition cancels and replaces the second edition published in 2012. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
- the document has been updated to be in alignment with the second edition of IEC 62271-1:2017;
- rated TRV has been removed (TRV is only a test parameter), as in the latest revision of IEC 62271-100;
- differentiation has been introduced between requirements expressed for fulfilling the function expected from a switch-fuse combination, from requirements only relevant when the function is performed by a stand-alone device. The goal is to avoid duplication or conflicts of requirements with a standard dealing with assemblies, when the function is implemented within such an assembly.