scope:

This standard applies to three-pole units for public and industrial distribution systems which are functional assemblies of switches including switch-disconnectors and current-limiting fuses and thus able to interrupt:

- any load current up to the rated breaking current of the switch;

- any over-current up to the rated short-circuit breaking current of the combination by which automatic interruption is initiated.

NOTE 1 - Besides by the fuse and its striker operation, automatic interruption may be caused by an over-current release and by self-protecting devices.

It does not apply to fuse-circuit-breakers, fuse-contactors, combinations for motor-circuits or to combinations incorporating single capacitor bank switches.

NOTE - 2 In this standard, the word "combination" is used in the following sense: a combination in which the components constitute a functional assembly.

The fuses are incorporated in order to extend the short-circuit rating of the combination beyond that of the switch alone. They are fitted with strikers in order both to open automa- tically all three poles of the switch on the operation of a fuse and to achieve a correct operation at values of fault current below the minimum breaking current of the fuses. In addition to the fuse strikers, the combination may be fitted with either an. over-current release or a shunt release.

NOTE 3 - In this standard the term "fuse" is used to designate either the fuse or the fuse-link where the general meaning of the text does not result in ambiguity.

This standard applies to combinations designed with rated voltages above 1 kV and below 52 kV for use on three-phase alternating current systems of either 50 Hz or 60 Hz.

The individual components of the combinations shall comply, in all relevant respects, with IEC 265-1, 282-1 and 787 quoted below.

NOTE 4 - Switches shall be in accordance with IEC 265-1 except for the short-time current and short-circuit making requirements where the current limiting effecfs of the fuses are taken into account.

NOTE 5 - Earthing switches forming an integral part of a combination are covered by IEC 129. If the earthing switch has a rated short-circuit making current, the making tests should be made in accordance with the requirements of IEC 265-1.

NOTE 6 - This standard also applies to switch-fuse combinations when included in ring main unit format.