Hyderabad Metro Rail project touted to be at global standards being executed under first ever private-public partnership (PPP) model has shunned modern Third Rail technology of power supply for the train, and decided to stick to the age-old overhead line system called AC Traction. Shockingly, the reason given is lack of skilled engineers able to handle the modern technology. “The intention is to adopt a cutting edge technology in every possible aspect of the Hyderabad Metro Rail project. However, when it comes to seamless power supply for the train, we preferred a bit old trend of AC Traction, considering paucity of trained engineers able to handle Third Rail system that is modern trend across the globe. People need to be trained before going for such modern technology, and for now it is safe to settle for overhead line,” said a senior official in Hyderabad Metro Rail Limited (HMRL).
However, in Bangalore the metro rail project has used the Third Rail system successfully, and even in Delhi the latest technology is adopted for the third stage of the metro rail in the stretch between Delhi and Gurgaon without any hitch. Interestingly, L&T that is executing Hyderabad Metro Rail project as the concessionaire is also the builder of Bangalore Metro Rail project. And there is no convincing answer from HMRL authorities on this discrepancy. Third Rail system is the modern technology wherein the power supply line is placed in between the two track of the rail, and the train gets the seamless power supply as it runs on the tracks, where as the AC traction system supplies the power through an overhead line running along the track. The third line system supplies 750 volt DC voltage (direct current voltage, while the overhead line system provides 25 KV AC (alternative current voltage). And the experts feel, by any standard the third line system is preferred to the age-old overhead line system, as the modern trend call for. The overhead line system is not only deterrent to the aesthetics matching to the modern urban transport system such as metro rail, but also scores negatively in terms of cost effectiveness.
“Any modern metro rail project uses the Third Rail system for power supply, as it is cost effective and minimizes the maintenance issues. The structure cost, and maintenance cost is at higher side for AC Traction system apart from it is being considered as an old trend, across the globe, as far as esthetics is concerned,” said Prof. M N Srihari, advisor to the Government of Karnataka on infrastructure and traffic, who is over viewing Bangalore metro rail project. According to Srihari’s estimation, the Third Rail system costs over 25 % less than the AC Traction system. However, authorities at HMRL are looking at it from safety point of view given the engineers are trained in the old overhead line system, and they told TOI that they didn’t want take risk. “The biggest issue here is safety. We feel the overhead lines are safer, as we are well versed with the system. With the Third Rail system, risk involves in evacuation the passengers, when the train trains stops in middle due to any technical snag. And it is riskier near stations, where the movement of the passengers is at its maximum,” said the HMRL official.
He said with over head line system, the rolling stock (train set including engines and bogeys) with higher passenger capacity up to 80000 phpdt (peak hour peak direction traffic), while the rolling stock with third rail system could handle just 50000 phpdt. He also said the AC Traction was cost effective in terms of energy consumption, as the third rail system used DC power that is expensive. The authorities said HMRL had entered an agreement with AP Transco for uninterrupted power supply to the railway traction and also for station and depots. About 75 MW of power will be required a day for the project. Transco will be supplying 130 KV power, which will be scaled to 25 KV for traction.