Abstract: Large railway hub stations are the core nodes ensuring the operation of electrified railway transportation. Characterized by numerous tracks, diverse locomotive types, and complex load conditions, their traction power supply systems serve as the energy hubs of the stations, and voltage stability has a significant impact on system operational safety. In actual operation, when high-speed, conventional passenger, and freight trains operate simultaneously, bus voltages of traction substations frequently exhibit amplitude fluctuations. This paper takes the power supply system of a large railway hub station as the research object and investigates the influence of short-circuit capacity and power factor on traction network voltage based on long-term power quality monitoring data. The results indicate that short-circuit capacity directly affects voltage stiffness, making bus voltage more susceptible to fluctuations under large traction impacts, while excessive reactive power further intensifies the frequency and magnitude of voltage fluctuations. This study reveals the main characteristics of voltage fluctuations in railway hub stations and provides data support and theoretical reference for the safe and stable operation of traction power supply systems.