Transition and Issues of Substation Protection Relay Systems for Power Distribution

In June 2023, the Protection Relay System Technical Committee planned a special issue labeled as “Protection Relay System Technology in Power Distribution Stations”. Protection relay systems play a vital role in the stable operation of power systems. In recent years, they have also been responsible for solving various problems in power systems, such as the realization of mass introduction of renewable energy, expansion of the operational capacity of power distribution facilities, and rationalization of facility configuration. The following topics were gathered and discussed as a result of the call for this special issue.: (1) Proposals for distribution line protection methods (short circuit protection, ground fault protection), (2) Case studies using IEDs (IEC 61850), N-1 inter trip scheme, bus bar protection relays, and comprehensive retrofits, (3) Optimizing accident recovery during distribution line accidents, (4) Voltage adjustment methods using storage battery capacity operation, (5) Bank Recorder and switchboard configuration when dealing with reverse power flow. A total of 10 papers were submitted. This commentary touches on the contents of the technical reports as an aid to understanding these papers. It also outlines the history of distribution substation protection relays and the latest technology in distribution substation protection relay systems. © 2023 The Institute of Electrical Engineers of Japan.