An Advanced Protection Scheme for Enabling an LVDC Last Mile Distribution Network

Low voltage direct current (LVDC) distribution systems have the potential to support future realization of smart grids and enabling of increased penetration of distributed renewables, electric vehicles, and heat pumps. They do, however, present significant protection challenges that existing schemes based on dc fuses and conventional electro-mechanical circuit breakers cannot manage due to the nature of dc faults and slow device performance. Therefore, this paper presents an advanced protection scheme that addresses the outstanding challenges for protecting an LVDC last mile distribution network. The scheme takes advantage of advanced local measurements and communications that will be naturally integrated in smart grids, and the excellent level of controllability of solid state circuit breakers. It thus provides fast dc fault detection and interruption during dc transient periods, in addition to achieving fault limitation and fast reliable restoration. The introductory part of the paper quantifies the potential benefits of LVDC last mile distribution networks, and discusses the potential LVDC architectures that best utilize the existing plant. Based on the new LVDC architectures, a typical U.K. LV network is energized using dc and modeled, and is used as a case study for investigating the protection issues and evaluating the new protection scheme performance through simulation.