Operational experience with current-limiting series reactors in conventional substation within the Indian grid

India’s national transmission system functions as a single unified grid formed by the synchronisation of five regional networks. In the Northern Region, several 400 kV substations built during the 1990s—originally designed for much lower fault levels—have become part of an expanded and stronger 220 kV and 765 kV transmission network. Rapid load growth and significant additions in Extra High Voltage (EHV) transmission and generation have reduced system impedance, causing short-circuit levels to rise beyond the design capability of older switchgear, creating risks of overstressing and equipment failure.To control these elevated fault currents, multiple mitigation options were studied, including bus splitting, replacement of existing switchgear, and installation of series current-limiting…