Short-circuit analysis of pumped storage unit during back-to-back starting

Back-to-back starting is a widely accepted starting method for pumped storage units. A back-to-back starting model of pumped storage units was built using the ElectroMagnetic Transients Program including DC (EMTDC) software package. The short-circuit fault during back-to-back starting was investigated for the first time. The starting process was simulated and compared with real data from a pumped storage power plant in northeast China. The rotor speed and the effect of resistance during fault period were also discussed. The results showed that the fault current has significant magnitude and low-frequency characteristic. Recommendations were provided to realise secure and reliable fault clearance during back-to-back starting based on the fault characteristics and real de-excitation test results of the pumped storage power plant.