Protection of LVDC networks integrating smart transformers: the case of LV engine Falkirk trial site

To enhance the adaptability of low voltage (LV) networks and release additional network capacity towards enabling the wider uptake of low carbon technologies, SP Energy Network's (SPEN) LV Engine project aims to design and trial the first UK solid state transformer (SST) for deployment within secondary substations (11/0.4kV). The trial site at Falkirk Stadium that is aimed to be completed in the near future will form the first LVDC trial at a utility scale in the UK. The SST and the introduction of low voltage DC (LVDC) supplies will present fundamental changes in the operation of existing secondary substations and will introduce new LV fault profiles for the associated LVDC distribution networks. This paper presents the results of joint work between the University of Strathclyde, SPEN and WSP with the primary objectives to understand the impact of SST deployment on the fault behaviour of LVDC networks and develop adequate protection strategies for LV Engine LVDC trial sites.