HV Fuses with Improved Cyclic Stability ICS®

For decades, high-voltage (HV) fuses have provided economical and most reliable protection of electrical applications standardized by IEC60282-1[1]. They fulfil both either the protection of the circuit components or the energy limitation, fast disconnection to limit negative effects to the corresponding network. They are often used in combination with a second switching-device of limited switching capacity. Typically, such kind of medium-voltage switching - or control-gears handle the switching tasks of the pure operating current of the application up to a certain, but limited level of short-circuit current. In the event of a high-current fault, occurring either on the grid or in one of the components, failure currents may arise which exceed the breaking capacity of this switching device. This is where the “high-voltage high-breaking- capacity fuses” – or HV fuses for short – step in. The development of more compact and economical switchgear solutions requires HV fuses with a reduced power dissipation are still able to handle higher transformer capacities. These now available so-called “Low Loss” fuses [2] provide the well-known protection of transformer circuits even in case of higher transformer capacities up to 3.000 kVA in combination with encapsulated switchgears subjected to IEC 62271–105 [3] as applied in actual renewable applications like wind or solar farms of a higher power level. However, before the “Low-loss” fuses were available HV fuses were also used inside renewable energy systems of a reduced power level. After some years of operational experiences, it became obvious that special attention has to be paid to the additional issue of cyclic stability due to current fluctuations given by nature in case of such renewable energy systems. SIBA decided to take care of this matter by developing a corresponding melting-element system and fuse series with an enhanced cyclic stability called ICS. This new fuse series can be seen as a second step and further development of the known “Low-loss” type. In addition to the improved power loss and thermal situation, this new type is providing an enhanced mechanical cyclic stability in case of current fluctuations inside renewable energy systems.