Abstract: Regarding the transient stability problems of synchronous condensers（SCs） in renewable energy stations, analyzing the influence factors and revealing the influence mechanisms are the keys for studying the stability control schemes and improving stability capabilities. Based on the typical open-phase operation scenario after a single-phase fault occurs on a renewable energy transmission line, the influence of key factors including electrical distance, SC inertia, and the control strategy of renewable energy on SC transient stability is analyzed by adopting the equal area criterion. Simulation verification is conducted on the equivalent system of a renewable energy sending-end system and the modified IEEE 39-bus system with renewable energy and SCs. The results indicate that the large-scale and long-distance transmission of renewable energy and the deep low voltage ride-through（LVRT） control strategy have adverse effects on the rotor-angle stability of SCs, and the transient stability is stronger with the larger inertia of SCs. As the active power recovery rate of renewable energy decreases, the rotor-angle stability of SC shows a trend of decreasing first and then increasing. In addition, by comparing the power delivery limits of renewable energy under different constraints, it is known that adding SCs can significantly improve the power delivery limits of renewable energy constrained by voltage safety or short-circuit ratio. However, the rotor-angle stability constraint caused by SCs will also become a new bottleneck that limits the further improvement of power delivery capacity of renewable energy.