AS 2024-1991

Specifies requirements for three-pole switch-fuse combinations having rated voltages above 1 kV up to but not including 52 kV for use in three-phase a.c. systems. Covers combinations in which the switch is opened by fuse-striker action with or without the operation of other tripping devices.

This Standard specifies requirements for three-pole switch-fuse combinations having rated voltages above 1 kV and up to but not including 52 kV, for use on 50 Hz three-phase a.c. systems.It covers functional assemblies of switches or switch-disconnectors complying with AS 1025.1 in combination with current-limiting fuses complying with AS 1033.2, with strikers, which together are able to interrupt currents up to the rated short-circuit breaking current of the switch-fuse combination as follows:(a) The fuses extend the short-circuit rating of the combination beyond that of the switch alone. The fuse strikers cause all poles of the switch to open when a fuse element melts.(b) The switch of a switch-fuse combination may, in addition to the fuse strikers, be operated by either an overcurrent release or a shunt release.This Standard covers combinations forming part of ring main units.This Standard does not cover switch-fuse units with dependent manual operation, fuse-circuit-breakers, switch-fuse units specially designed for motor circuit applications, e.g. with special overload requirements, switch-fuse units for switching capacitor banks, or combinations of a switch and fuses in which all poles of the switch are not caused to open by the operation of a fuse striker.NOTES:1. Switch-fuse combinations are subsequently referred to as 'combinations' in this Standard.2. The term 'fuse' used in this Standard may designate either a fuse or a fuse-link where it does not result in ambiguity in the meaning of text.3. Switches in combinations need not comply with the short-circuit making requirements of AS 1025.1 for compliance with this Standard when the current limiting effects of the fuse-links are taken into account.4. Earthing switches complying with AS 1306 may, in addition, form part of a combination. However if the earthing switch is required to have a short-circuit making current, its rated making current needs to be verified by test in accordance with AS 1025.1.This Standard has to be read in conjunction with AS 2650. Its clauses are aligned with the clause numbers and headings in AS 2650 and the application of the specific requirements of AS 2650 is stated throughout this Standard.