DIN EN IEC 62271-105:2024-05

This part of IEC 62271 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 document applies to combinations designed with rated voltages above 1 kV up to and including 52 kV for use on three-phase alternating current systems of either 50 Hz or 60 Hz. In this document, the word "combination" is used for a combination in which the components constitute a functional assembly. Each association of a given type of switch and a given type of fuse defines one type of switch-fuse combination. Different types of fuses can be combined with one type of switch, which give several combinations with different characteristics, in particular concerning the rated continuous currents. A switch-fuse combination is therefore defined by its type designation and a list of selected fuses defined by the manufacturer, the so-called "reference list of fuses". Compliance with this document of a given combination means that every combination using one of the selected fuses is proven to be in compliance with this document. The fuses are incorporated in order to extend the short-circuit breaking rating of the combination beyond that of the switch alone. They are fitted with strikers in order both to open automatically all three poles of the switch on the operation of a fuse and to achieve a correct operation at values of fault current above the minimum melting current but below the minimum breaking current of the fuses. In addition to the fuse strikers, the combination can be fitted with either an over-current release or a shunt release. In this document, the term "fuse" is used to refer to either the fuse or the fuse link, provided that this does not cause ambiguity in the general meaning of the text. Fuses are in accordance with IEC 60282-1:2020. Switches, including their specific mechanism, are in accordance with IEC 62271-103 except for the short-time current and short-circuit making requirements where the current-limiting effects of the fuses are taken into account. Earthing switches forming an integral part of a combination are covered by IEC 62271-102. In addition, switches which include other functions (not covered by IEC 62271-103) are covered by their relevant standards (for example, IEC 62271-102 for disconnectors and earthing switches). This part of IEC 62271 does not apply to combinations of fuses with circuit breakers or contactors, nor to combinations for switching motor circuits or single capacitor banks. Devices that require dependent manual operation are not covered by this document. The standard differs from DIN EN 62271-105 (VDE 0671-105):2013-08 as follows: a) the technical changes introduced in the second edition of IEC 62271-1 have been implemented where relevant; b) 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.