Shortlisting Protection Configurations for HVDC Grids and Electrical Energy Hubs

This paper proposes a methodology for shortlisting protection system configurations for large HVDC switching stations, which are expected in multiterminal HVDC grids and electrical energy hubs (or energy islands). This novel approach focuses on the configuration of protection equipment and the arrangement of lines and converters in various protection zones, instead of expert decisions on protection strategies based on numerous simulations. A graph-based approach that allows high-level evaluation of possible DC fault impacts is presented. This fault impact evaluation method can evaluate many possible protection configurations allowing the selection of less obvious choices, as experts cannot consider all possible configurations, especially when the switching station size increases. A filtering process is applied to reduce the number of possible configurations based on multiple protection performance metrics which are evaluated for different power flow scenarios. The results for these performance metrics can be compared for configurations with different numbers of HVDC circuit breakers to assess the benefit of increasing the amount of protection equipment in different network topologies. It is also shown that, through continued filtering using additional performance metrics or fault scenarios, the number of possible breaker, cable and converter configurations can be further reduced, leading to a protection design that is well suited for many operational scenarios. The results of the shortlisting process provide insights on the required number of HVDC circuit breakers to limit fault impacts to a given value. Moreover, observed trends in the results could, in future studies, contribute to new design principles and priorities, allowing system developers to more effectively design HVDC protection systems for different operational scenarios and possible investment levels.