Transient Simulation and Analysis of Runaway Conditions in Pumped Storage Power Station Turbines Using 1D–3D Coupling

Pumped-storage power plants play a vital role in power systems by providing peak load regulation, frequency control, and phase modulation services. The safety and stability of these plants critically depend on understanding transient processes during frequent unit start–stop cycles and operational transitions. This study employs 1D–3D coupled numerical simulations to investigate a pump–turbine unit’s external characteristics, pressure pulsations, and internal flow dynamics under turbine runaway conditions. At the runaway rotational speed of 650.9 r/min, large-scale vortices with intensities exceeding 500 s−1 form at the inlet of specific runner blade passages, severely obstructing flow. Concurrently, the tailwater pipe vortex structure transitions from a central spiral pattern to a wall-attached configuration. The concurrent occurrence of these phenomena induces abrupt runner force variations and significant pressure pulsations, primarily comprising high-frequency high-amplitude pulsations at 1× and 2× blade frequency attributable to runner dynamic-static interference; broad-spectrum high-amplitude pulsations resulting from operational transitions; and low-frequency high-amplitude pulsations induced by the tailwater pipe vortex belt.