萧山发电厂西门子V94.3A燃气-蒸汽联合循环机组在启动及运行期间，多次因汽包水位保护动作引起机组跳闸。根据汽包水位变化的主要机理，从水位调节控制系统、高中压旁路及给泵选型等热力系统设计几个方面对跳闸原因进行了分析，提出了通过控制速率、中压旁路最小压力设定、设置高压旁路减温超驰功能3个方面对旁路控制进行优化，同时通过给水控制的优化，实施对汽包水位的有效控制。优化措施实施后取得了较好效果，提高了汽包水位控制系统运行可靠性。

During the startup and operation of SIEMENS V94.3A gas-steam combined cycle unit in Xiaoshan power plant, the unit frequently tripped due to drum water level protection. Based on the mechanism of drum water level fluctuation, the root causes for the trip are analyzed in thermal system design, such as water level control system, high & medium pressure bypass system, as well as selection of the feed water pump. As a result, the bypass control is optimized by controlling load speed, and setting the minimum pressure of the intermediate pressure bypass and attemperating function of the high pressure bypass. In addition, the feedwater control is also optimized for successfully control the drum water level. After the optimization, great effect has been achieved and operational reliability in the control system of drum water level is enhanced.