It is important for HV Fuse-Links that they must be operated at the voltage for which it has been rated. Accordingly, the operating voltage corresponds to the maximum rated voltage of the Fuse-Link. Owing to the switching voltage occurring during arcing, the Fuse-Link cannot be used at lower voltages without limitation. A lower operating voltage at which the Fuse-Link can still be used without exceeding the system insulation level during extinction must therefore be taken into account.

The breaking capacity is also referred to as the “rated maximum breaking current”. This clearly indicates that this is the maximum current which can be interrupted by the Fuse-Link. I1 of the Fuse-Link must be greater than the maximum short-circuit current at the site of the Fuse-Link (I1 > IKmax.

The minimum breaking current is referred to as the “rated minimum breaking current”. This value must be specified for backup Fuse-Links. From this current, back-up Fuse-Links are capable to breaking fault currents. The Fuse-Links must be assigned to the system so that no fault current below I3 can occur at the site of the Fuse-Link (due to the system parameters or other protective devices).

The power dissipation of a HV Fuse-Link is specified at the rated current of the Fuse-Link. For protection with HV Fuse-Links, it should be noted that the operating current is normally half the rated current. Because of the physical relationships, the actual power dissipation is less than a quarter of the value Pwarm for HV Fuse-Links shown in the technical data table.

The time-current characteristic shows the correlation between current and time up to the melting of a fuse-element. The virtual time (tvs) is specified to enable a comparison of the l/t characteristics of Fuse-Links below 100 ms. For co-ordination with other protective devices, e.g. switches or circuit breakers, the melting energy I2t must be referred to for melting times below 100 ms