The Centre has sanctioned Rs 6,717.2 million (mn) for an electrical infrastructure upgrade on the north-south corridor of the Kolkata Metro Blue Line. The works aim to raise train frequency, reducing peak-hour gaps from five minutes to two-and-a-half minutes by 2030, according to a Press Information Bureau release dated May 2. The package forms part of a broader plan to strengthen capacity on the city’s oldest metro corridor. Of the total, Rs 2,910.6 mn will be deployed to install seven additional traction substations, while the remaining Rs 3,806.6 mn will fund the replacement of transformers, rectifiers, high-speed circuit breakers and a network of cables. Engineers explained that shorter headways require a traction substation at or near each station to ensure adequate power delivery. The new substations are intended to modernise ageing electrical systems and reduce dependence on older infrastructure. The Blue Line was built in the 1980s and currently comprises 26 stations, 13 traction substations and five receiving substations. At present receiving substations accept 33 kV alternating current from the utility and step it down to 11 kV before feeding traction substations, which then convert power into 750 volts direct current for the third rail. Advances in technology now allow traction substations to handle 33 kV directly, diminishing the role of ageing receiving substations. Eight additional traction substations would provide a near one-for-one ratio with stations and an extra unit will be placed between Dum Dum and Belgachia to address a longer gap. Two new substations at Chandni Chowk and Gitanjali are nearing completion and are due to be functional by July-end. The programme will replace the steel third rail with an aluminium one to reduce voltage drops, cut energy losses and improve acceleration, and will be implemented in phases, with most underground sections already upgraded and the elevated stretch between Tollygunge and Kavi Subhas remaining.