核电厂半速汽轮机并网导致一回路过冷问题的分析与改进

Analysis and Improvement of Primary-Loop Too Cold Caused by Half-Speed Steam Turbine of Nuclear Power Plant Connected to Grid

当前国内核电厂半速汽轮机的控制和保护多采用法国的P320 TGC SV2+系统。根据系统逻辑设计,并网带最小负荷蒸汽需求(SD)会受到实际网频变化的影响,导致并网时初始负荷的SD存在不确定性。当SD过大时,一、二回路负荷出现不匹配,导致汽轮机旁路系统(GCT)阀门全部关闭,一回路出现过冷。通过对并网带最小负荷设计原理进行研究,指出了该并网逻辑的弊端,同时对比机组历次并网数据,对并网方式进行优化。当功率超过40 MW时,将并网方式由开环控制改为闭环控制;当功率低于40 MW时,维持原有的开环控制方式。同时,对逻辑中的目标负荷设定值变化速率进行优化,大大缩短了操纵员手动干预所需要的时间。通过对并网方式的优化和设计逻辑的修改,提高了机组的可靠性,为处理同类机组汽轮机调节系统(GRE)并网带最小负荷过程中一、二回路负荷不匹配导致的过冷问题提供了借鉴。

At present,the control and protection of half-speed steam turbines in domestic nuclear power plants are mostly based on the French P320 TGC SV2+system.According to the systematic logic design,the grid-connected minimum load steam demand(SD)will be affected by the actual power grid frequency change,resulting in the uncertainty of the SD of the initial load when grid-connected.When the SD is too large,the load of the primary-loop and secondary-loop does not match,causing the turbine bypass system(GCT)valves to be fully closed,and the primary-loop is too cold.Through the research on the design theory of grid-connected with minimum load,the malpractice of the grid-connected logic is pointed out,and all the grid-connected data are compared,the mode of grid-connected is optimized.When the power exceeds 40 MW,the grid-connected mode will be change from open-loop to closed-loop,when the turbine power is lower than 40 MW,the grid-connected mode will keep the open loop control.In addition,the variation rate of the target load setting of the logic is optimized,which greatly shortens the time required for the operator to intervene manually.Through the optimization of the grid-connected mode and the modification of the logic design,the reliability of the unit is improved.It provides a reference for the same type of turbine control system(GRE)to solve the too cold problem caused by mismatch of primary-loop and secondary-loop in grid connected with minimum load.