CEI EN 60549

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).