Design Of Control And Protection System For Nuclear Power Half Speed Steam Turbine

Nuclear energy will provide 8%~10% of the electricity in 2030 according to the 13 th Five-Year Plan made for national energy development and the third generation nuclear power projects of coastal are being constructed in an orderly manner as planed.In nuclear power station,the most important part of conventional island is turbogenerator and its related systems.The control and protection system in turbogenerator affects the operation efficiency and safety performance of nuclear power station.The control system provides plant-wide control during unit start-up,load lifting,power operation,stack shutdown and refueling.While,the protection system is used to monitor the important operation parameters of steam turbine.As the importance of control and protection system of turbogenerator,it is meaningfull to analyses the logic of the control system,arrange the structure of the protection system and monitoring system,summarize and analyses the start condition and technological process and design the control and protection system of the AP1000 third generation nuclear power steam turbine.In this study,we researched the control system of steam turbine in nuclear power station and the frequency regulation of the original scheme and found that the frequency regulation function of the original scheme can not satisify the user's requirements for power quality and frequency stability of network.Then,according to the requirement privided by South China Power Grid for the frequency regulation capability of nuclear power units,the primary frequency regulation function of the existing steam turbine control system is redesigned to solve the problem of participating in the frequency regulation under the regulator control mode and regulateing the range of frequency regulation by introducing the primary frequency regulation function combined with frequency regulation dead zone and speed inequality.Meanwhile,the introduction of primary frequency regulation function can increase the range of frequency regulation dead zone,avoiding the frequent load up and down on the side of nuclear island caused by the frequency disturbance of the network.In addition,based on the analysis of the interface between the turbine protection system and the turbine monitoring system,we found the risk of signal point failure of electromagnetic relay of each signal and receiving signal,the increased failure points caused by complex structure of carbinet system and the increasing response time of system induced by electromagnetic relay and proposed a new interface mode based on the quadruple redundancy turbine protection system.This interface was designed based on two redundant relay frames to output redundant jump signals and avoid the risk of a single failure.By doing this,the number of hard wiring between the turbine monitoring system,the turbine protection system was decreased,the response time of the turbine protection system was shortened,the structure of system was simplified and the number of system failure points was reduced.On the foundation of research of steam turbine and its related systems,the sequential control start-up strategy of steam turbine was put forward under the trend of intellectualization of power station control and the auxiliary system,main steam system and steam turbine valve control system were integrated.Through the systematic research on the start-up,load and shutdown process of steam turbine,the sequential control logic of steam turbine was designed,which greatly reduced the operation tasks of operators,and integrated all kinds of states of units into the sequential control system.Then,the sequential control system judges step by step according to the start-up sequence to make unified judgement and response qualified judges before proceeding to the next step.If it failed to meet the start-up requirements,relevant reports for warning will be issued to inspect and deal with the problem locally.Then the sequential control system will automatically judge the next step after processing to reduce the influence of human intervention on system security.