A short circuit current study for the power supply system of Taiwan railway

The western Taiwan railway transportation system consists mainly on a mountain route and ocean route. Taiwan Railway Administration (TRA) has conducted a series of experiments on the ocean route in recent years to identify the possible causes of unknown events which cause the trolly contact wires melt down frequently. The conducted tests include the short circuit fault test within the power supply zone of the Ho Long Substation (Zhu Nan to Tong Xiao) that had the highest probability for the melt down events. Those test results based on the actual measured maximum short circuit current provide a valuable reference for TRA when comparing against the said events. Le Blanc transformer is the main transformer of the Taiwan railway electrification system. The Le Blanc transformer mainly transform the Taiwan Power Company (TPC) generated three phase alternating power supply system (69 kV, 60 Hz) into two single phase alternating power distribution system (M phase and T phase) (26 kV, 60 Hz) needed for the trolly traction. As a unique winding connection transformer, the conventional software for fault analysis will not be able to simulate its internal current and phase difference between each phase currents. Therefore, besides extracts of the short circuit test results, this work presents a EMTP model based on Taiwan Railway Substation equivalent circuit model with Le Blanc transformer. The proposed circuit model can simulate the same short circuit test to verify the actual fault current and accuracy of the equivalent circuit model. Moreover, the maximum short circuit current is further evaluated with reference to the proposed equivalent circuit. Preliminary inspection of trolly contact wire reveals the possible causes of melt down events based on the simulation results.