Control of Indigenous Automatic Switched Neutral Section - A Revolution in Railway Traction Power

In 25kV electric traction power supply system, traction substations are fed on single phase supply. In case the single-phase traction load is supplied through only one phase, an unbalance is caused in three phase system of the power utilities. In order to reduce this unbalance effect, the adjacent traction sub stations along the train routes are fed in sequence in such a way that all the three phases are utilized & unbalance is reduced to bare minimum. These phases of power supply are electrically isolated from each other by neutral sections, usually installed near the traction substation (TSS) and sectioning post (SP). However, at 500 m short of such locations, sign boards are provided to guide the train's loco pilots that DJ (Locomotive Circuit Breaker) should be opened, so as to avoid bridging and in turn flashing of two adjacent phases of power supply. These sign boards are not clearly visible during the foggy & severe polluted conditions. More over this puts the loco pilots under unnecessary stress during the train run. Thus, a need was felt to develop a scheme wherein loco pilots do not have to switch on & off DJ frequently while negotiating the neutral section territory. This document is a showcase of the solution of this problem, wherein, use of Automatic Switched Neutral Section (ASNS) in 25 kV Ac electric traction network has made it possible to reduce the strain on loco pilots of the train running on electric traction, which was not possible till now. The scheme has been successfully planned, executed, implemented, tested, validated & implemented on running train routes of Indian Railways network for the first time with the help of indigenous resources. There is no interruption of the power supply from overhead equipment (OHE) to the locomotive and continuous operation of the all-electrical equipment on the train is ensured while negotiating the ASNS.