Load rejection is one of the dangerous transient scenarios in pumped-storage power stations (PSPSs), and the risk should be evaluated from design to operation stages of PSPSs. In this study, the extreme case with simultaneous load rejection of two pump-turbines in a prototype pumped-storage system was simulated by using the one-dimensional and three-dimensional (1D-3D) coupled computational fluid dynamics (CFD) method. The aims are to evaluate the risk of pressure fluctuations during this scenario comprehensively and assess the feasibility of the newly developed 1D-3D coupled approach in engineering applications. The results show that the maximal pressures (superimposed by water hammer and pulsating pressures) upstream of the runner exceed the industry standard. The largest maximal pressure and the longest overpressure duration occur in the vaneless space and are caused by the strong rotor-stator interaction (RSI). The strong RSI may be attributed to the unevenly distributed high gradient regions of pressure aroused by the uneven radial velocity pattern with obvious reverse flow at the runner inlet. This attempt revealed the mechanism of severe pressure pulsations during transient processes and demonstrated that the 1D-3D coupled method is feasible for engineering applications, especially in evaluating the transient risk of new ultrahigh-head PSPSs.

甩负荷是抽水蓄能电站（PSPS）中危险的瞬态情况之一，应从PSPS的设计到运行阶段评估风险。在这项研究中，通过使用一维和三维（1D-3D）耦合计算流体动力学（CFD）方法，模拟了原型抽水蓄能系统中同时消除两个水轮机负荷的极端情况。目的是全面评估这种情况下的压力波动风险，并评估新开发的1D-3D耦合方法在工程应用中的可行性。结果表明，流道上游的最大压力（由水锤和脉动压力叠加）超过了行业标准。最大的最大压力和最长的超压持续时间出现在无叶片空间中，并且是由强烈的转子-定子相互作用（RSI）引起的。较强的RSI可能归因于径向速度模式不均匀引起的压力分布不均匀的高梯度区域，流道入口处有明显的逆流。这项尝试揭示了瞬态过程中严重压力脉动的机理，并证明了1D-3D耦合方法对于工程应用是可行的，尤其是在评估新型超高扬程PSPS的瞬态风险中。