Failure of LV ASD supply-side fuses due to MV motor fuse operation

Transients in MV networks due to MV motor fuse operation can propagate through MV/LV transformers to LV networks. The LV surges can then cause the high-speed fuses protecting LV adjustable speed drives (ASDs) to operate and this can disrupt production. LV ASDs often include supply-side reactors to make them less susceptible to surges (in particular capacitor-switching surges). For the network studied, these reactors did not prevent operation of the particular ASD highspeed fuses. One possible reason was that the supply-side reactors were saturating during the surge conditions associated with MV fuse operation. This paper describes the investigation that included initial measurements, a simulation study so that various proposed solutions could be compared, and final measurements with the final recommended solution in place -supply-side reactors that did not saturate during these surge conditions.