某电厂因汽轮机偏周波运行引起停机事故。基于对汽轮机偏周波运行事故过程的分析，得出高、低压旁路后蒸汽温度波动频繁及事故停机的主要原因是高压排汽逆止门未开启而汽轮机带大负荷、造成高排金属温度高。分析了切除高压缸带大负荷对汽轮机的危害，提出了有关偏周波保护、低旁减温水、高压排汽逆止门的逻辑组态建议。运行实践表明：该逻辑组态方案可以避免事故发生，并且安全、可靠。

A shut-down accident occurred in a power plant because of turbine’s partial frequency operation. The main reasons of frequent fluctuations of steam temperature behind high and low pressure bypass in HP casing exhaust lie in high metal temperature, which is caused by the closed non-return valve and the heavy turbine load. Meanwhile, the harm to turbines caused by the removal of high pressure cylinder under large load is analyzed. Finally, some suggestions on logical configuration of partial frequency protection, desuperheating water of low pressure bypass and non-return valve are proposed in HP casing exhaust. The operation practice show that the logical configuration scheme could avoid accidents and be safe and reliable.