The Indian Central Railways is making history as the last bastion of the 1,500V Direct Current (DC) electrified lines in Mumbai has been carefully replaced with comparatively newer standards of the 25,000 volt Alternate Current (AC) traction followed across India. With this conversion from 1500 volt DC to 25,000 volt AC traction between Chhatrapati Shivaji Terminus(CST) and Thane on Monday, the only remaining lines in India which still run on DC traction are between CST and Panvel and the Thane-Vashi trans-harbour lines. India’s history of electric traction There are two main voltages used for mainline trains in India – 1,500 volt DC and the comparatively newer 25,000 volt AC. Over the years, different lines, including the Madras suburban routes, have been converted from 1.5 kV DC to 25 kV AC. Set up in 1925, the Mumbai suburban section was electrified with the 1,500v DC traction system. The advantages of the conversion means improved speed which provides better frequency of trains and fewer breakdowns. According to Central Railways which covers a large part of Maharashtra, major benefits will also include 33% energy saving because of regenerative breaking and extra time saving as the new generation Electric Multiple Unit runs at 100 kmph rather than at 80 kmph. An albatross around Central Railway’s neck However, the Rs 1300 crore conversion project, which was started more than a decade ago, has missed several deadlines. One of Central Railway’s top officials even called it an “albatross around CR’s neck”, according to DNA. Many of the British-era bridges passing over railway tracks have not been raised in height in the region, which led to issues of insufficient height between tracks and the overhead lines. During testing it was found that at nine locations between CST and Thane the prescribed gap was less than the required 4.27 metre. Since motor coaches of Siemens local trains running between stations, Kurla and CST, are 2 cm taller, it was found that they pushed the overhead lines higher. This had the potential to create a problem once their power was changed from 1,500 volt DC to 25,000 volt AC, reported Mid-Day. However, later the height of the trains was brought down by reducing the diameter of the wheels along with the height of the contact wire connecting the pantograph on the roof of the train with the overhead cables. Another issue they faced included slowing down of services as trains would have to run at a snail pace of 15 kmph at a few identified spots due to height restrictions. Later, authorities arrived at a solution and speed restrictions under bridges were also removed from four locations and increased to 30 kmph. However, efforts to ensure smooth conversion have paid off despite the complexity involved in dealing with one of the busiest networks of the Indian Railways. Over the years trains running in the Mumbai region have also been replaced with trains running on AC. The changeover was finally made in the early hours of Monday morning to cause minimum hindrance to the travelling commuters. Down the line, once the last remaining lines are converted to 25 kV AC, it will be the end of one chapter in the Indian Railways and a century’s worth of DC electric traction in the Indian Railways will come to a halt. (Image courtesy: Central Railway Facebook page)