Optimal operations of transformers in railway systems with different transformer operation modes and different headway intervals

Abstract

This paper presents an approach to the optimal operations of transformers in railway systems. Railway systems are supplied from bulk supply substations that consist of two transformers that are connected in the main-tie-main configuration. There are three operation modes for these transformers, namely non-parallel mode, parallel mode, and single transformer mode. Due to the fact that the traction loads are inherently dynamic, the optimal operation mode for the transformers requires a thorough simulation by including the train dynamics and train schedules. This paper aims to identify the optimal operation mode of the transformers under different headway intervals. In this study, the railway traction power system of the Mass Rapid Transit 2 (MRT2) in Malaysia is modeled and simulated in ETAP-Etrax Software with the dynamic load flow analysis to achieve an accurate estimation of transformer losses under the three transformer operation modes and different headway intervals. The results show that the parallel mode has lower transformer loss than that of non-parallel mode for all the headway intervals. It is also found that the single transformer mode has the lowest transformer losses for headway intervals of 5 min 48 s and above. Although the percentage of transformer loss reduction and the headway interval margin for optimal operation of single transformer mode may differ, this approach can also be applied to other DC railway systems.