Short-Circuit Analyses of Parallel and Non-Parallel Transformer Operations for Railway Power Supply: A Case Study for Third Rail System

It is a requirement to design a railway power supply system with redundancy to ensure the continuous power supply in the events of planned and unplanned outage. Typically, there are two transformers operating at the bulk supply substations, either in parallel or non-parallel mode. Parallel transformers operation contributes to a higher system reliability and transformer operating efficiency. However, such operation requires a higher kA rating of protective devices due to its lower system impedance. This paper aims to perform short-circuit analyses of parallel and non-parallel transformers operations for the third rail power supply and distribution system for Mass Rapid Transit 2 (MRT2) in Malaysia using ETAP software. It is found that parallel operation of transformers has a higher short-circuit current compared to that of non-parallel operation. The results of the short-circuit study can be used to determine the proper kA rating of protective schemes for the railway system.