High speed differential protection system for aircraft dc distribution systems incorporating solid state circuit breaking capability

The increasing adoption of the more-electric aircraft concept has seen a growth in the proposed use of power electronic systems and DC power distribution in order to attain numerous benefits. These include higher end-to-end power transfer efficiency, reduced power system weight through increased power density, and greater system flexibility and reconfigurability. However, there can also be significant safety challenges arising from an unconventional system fault response, which places challenging operating requirements on any protection systems employed. This paper presents a high speed current differential implementation approach for dc distribution systems capable of sub-millisecond fault detection. The approach utilizes the natural characteristics of dc differential current measurements to significantly reduce fault detection times compared to standard applications and hence meet requirements for dc converter protection. The paper first presents a review of potential protection issues associated with converter interfaced dc networks on aircraft which may necessitate accelerated protection operation. Options for implementing the proposed technique are then illustrated. Results of scaled hardware testing are presented which validate the overall protection operating times in a low voltage environment. These results show the implementation approach can consistently achieve protection system operation within the order of a few microseconds