Kolkata Metro's blue line becomes first in India to get battery backup system

Kolkata Metro’s Blue Line has become the first metro corridor in the country to be equipped with a Battery Energy Storage System (BESS), ensuring that trains will no longer remain stranded inside tunnels during sudden power failures. The 4 MW system has been commissioned along the underground stretch to enhance passenger safety and operational reliability.

The newly installed BESS, set up at a substation near Central station, is designed to automatically activate during grid failure or major power outages. In such situations, it will supply stored electricity to haul stranded rakes from mid-tunnel to the next station at speeds of up to 55 kmph. In the past, passengers were at times forced to walk along tracks to reach stations during extended outages.

Metro Railway officials said three successful trials were conducted with fully loaded rakes prior to commissioning. During one trial, a rake travelled nearly 20 km while switching to battery backup after power was cut. The system is capable of covering up to 35 km and can sequentially pull out 18 trains one by one in case of large-scale failure.

The BESS comprises inverters and Advanced Chemistry Cell (ACC) batteries powered by a 6.4 MWh Lithium Iron Phosphate (LFP) battery. Apart from hauling trains, it can also support tunnel ventilation and environment control systems at underground stations. Officials said the system has an estimated lifespan of around 14 years and is compact in design.

The project has been conceptualised under the National Programme on Advanced Chemistry Cell Battery Storage approved in 2021. Metro authorities said the green battery system will not only ensure commuter safety but also reduce carbon footprint, improve power factor, manage demand spikes and lower electricity bills across the network.