scope:

This part of IEC 62271 applies to three-pole operated units for distribution systems that are functional assemblies of a circuit-switcher and current-limiting fuses designed so as to be capable of: - breaking, at the rated recovery voltage, any load or fault 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. They are intended to be used for circuits or applications requiring only a normal mechanical and electrical endurance capability. Such applications cover protection of HV/LV transformers for instance, but exclude distribution lines or cables, as well as motor circuits and capacitor bank circuits. Short-circuit conditions with low currents, up to the fused circuit-switcher rated take-over current, are dealt with by supplementary devices (strikers, relays, etc.), properly arranged, tripping the circuit-switcher. Fuses are incorporated in order to ensure that the short-circuit breaking capacity of the device is above that of the circuit-switcher. NOTE 1 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 fused circuit-switchers 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. Comparison with other existing switching devices is provided in Clause 8. NOTE 2 Other circuit-switchers exist; see [1] 2. Fuses are covered by IEC 60282-1. Earthing switches forming an integral part of a circuit-switcher are covered by IEC 62271-102. Installation in enclosures, if any, is covered either by IEC 62271-200 or by IEC 62271-201.