This standard applies to external fuses used with high-voltage capacitors according to IEC 60871-1, Shunt capacitors for a.c. power systems having a rated voltage above 1 000 V – Part 1: General. IEC 60871-1 is applicable to both capacitor units and capacitor banks intended to be used, particularly, for power-factor correction of a.c. power systems, and also to capacitors intended for use in power filter circuits.
Fuses according to this standard are intended to clear either faults inside a capacitor unit to permit continued operation of the remaining parts of the bank in which the unit is connected (unit fuses) or faults on the whole capacitor bank to isolate the bank from the system (line fuses).
In this standard the terms “capacitive current” and “inductive current” are used to indicate test currents that have a leading or lagging power factor, respectively, and in which the circuit contains predominantly capacitive or inductive components. The word \'capacitor\' is used when it is not necessary to lay particular stress upon the different meanings of the word \'capacitor unit\' or \'capacitor bank\'.
In some cases, fuses tested only to IEC 60282-1 or IEC 60282-2 may be suitable for use with capacitors if they are not required to interrupt capacitive currents (e.g. if capacitive currents cannot flow, or if they are acting as a “back-up”, to provide high inductive current breaking, to other devices that will clear capacitive currents).