Evolution of protective relays in 1-Φ, 25kV, 50Hz railway traction system

This paper presents the evolution of protective relays used for the protection of Power Transformer, Over Head Equipment (OHE) and Shunt Capacitor Bank in Indian Railways Electrical Distribution Systems. Initially during electrification Indian Railways adopted 1-Φ, 25KV, 50Hz AC system and electromagnetic relays (EM Relays) for feeder protection of OHE available at that time. But over the period of time with the drastic growth in traffic and sharp increase in demand for more electrical power to heavy goods trains haulage, the above said protective system doesn’t catered the requirements like speed, sensitivity, reliability, post fault data analysis. Hence Indian Railways over the years have undergone a paradigm shift in protective relay schemes. The journey of evolution from EM relays and static relays to the latest state of art integrated Numerical relays which were approved by RDSO are dealt here.