Feasibility of adopting bilateral co-phase traction network in single phase 25 kV AC traction system

In this paper the Indian Railway traction network is analyzed. Indian Railways gets its traction supply from the state-owned utility grid. With the shift in policy to manufacture only 3-φ locomotives in the future, there shall be enhanced feedback of regenerative braking energy (RBE) to the grid especially in the absence of another 3-φ locomotive to absorb this RBE. This can negatively impact the utility grid (due to the harmonics in RBE) and presently there is no provision to get remunerated for this reverse flow of energy. Thus, it is essential to efficiently utilize this RBE in the railway network itself. This can be achieved by adopting bilateral co-phase traction network configuration which can enhance the utilization of RBE. However, by making the traction supplies co-phase in adjacent traction substations there is a pronounced effect of circulating currents which can offset any advantage obtained due to RBE utilization. In this paper the feasibility of adopting bilateral co-phase traction network is examined by demonstrating the impact of difference of voltage magnitudes and phase angles on effective RBE utilization. The ideal range of these parameters for saving RBE is also demonstrated. A case study is done based on realistic data from Indian Railways.