E-REDES: using legacy technology to foster electricity distribution network evolution

The traditional electricity distribution model is undergoing a paradigm shift with the increasing integration of distributed energy resources (DERs). This paper presents the development of enhanced remote telecontrol units (RTUs) by E-REDES, the main Portuguese distribution system operator (DSO), for underground MV distribution grids. These upgraded RTUs incorporate new technologies, such as low-power voltage and current transformers (LPVT and LPCT), to increase grid observability and enable advanced protection and control functionalities. LPVT and LPCT offer a space-saving solution for increasingly compact Ring Main Unit (RMU) bays. The enhanced RTUs enable the implementation of Directional Overcurrent and Directional Earth Fault functions without the need for breaker-tripping settings to flag fault direction. This is achieved by utilizing the Discrete Fourier Transform and a characteristic angle adapted to the neutral earthing system, as described in [1]. By identifying the fault direction during the transient phase, the solution is insensitive to different neutral earthing systems. This improved observability as sists grid operators in making critical decisions during grid events, defining optimal grid configurations, and minimizing network losses. The solution demonstrated good performance during an observation period, providing valuable information to grid operators.