Experience from research into low voltage DC distribution system protection : recommendations for protecting hybrid HV DC-AC grids

This paper presents experience and outcomes of a research project concerned with protecting an LVDC “last mile” distribution network. The paper introduces the following contributions that reduces the risks associated with shifting from AC to DC for LV distribution purposes: understanding of how an LVDC system behaves during fault conditions through presentation and analysis of simulation results; outlining the issues associated with using traditional LV overcurrent protection for protecting future LVDC networks; and simulation of a new DC protection scheme that provides fast DC fault detection and location with a good level of selectivity. In addition, the paper presents a discussion of the lessons learned from the LVDC protection research project and how they can be utilised to understand and address the protection challenges in a higher voltage hybrid DC-AC grid