1. Introduction The establishment of an optimized maintenance system for hydropower plant control systems is primarily due to current technological advancements. Control systems have evolved from conventional control to large-scale integrated circuits, with CPUs now serving as the core control unit. DSP technology is also used for peripheral data acquisition. This strengthens the system's self-diagnostic capabilities and significantly enhances its ability to exchange information with other systems. This allows on-site maintenance personnel to gain a more comprehensive understanding of system operation information, establish a comprehensive system fault information and status detection system, and conduct integrated evaluations. It also enables the development of necessary operation and maintenance guidance systems, which is highly beneficial given the current trend towards unmanned operation in hydropower plants, reducing maintenance personnel and improving equipment fault handling capabilities. 2. Basic Concepts of Optimized Maintenance Optimized maintenance, based on condition-based maintenance strategies determined by equipment operating status, incorporates information from the enterprise's management and control systems to achieve optimal economic benefits. It proposes corresponding maintenance decision-making methods. From its concept, it's easy to see that optimized maintenance incorporates the idea of ​​control, maintenance, and management compatibility. This technology, known as CMMS (Control-Maintenance-Management System), gradually emerged in Europe in the 1990s. Optimized maintenance systems are designed and developed based on the concept of optimized maintenance. They should be based on existing control equipment and maintenance objects, adding appropriate data acquisition equipment to monitor the status and output of the control system in real time, ensuring that the original system's control functions are not affected. This allows for the determination of whether a fault has occurred, quantitative analysis of anomalies, identification of the type, timing, manifestation, and severity of abnormal changes, and exchange with other information related to system control and management to propose comprehensive optimized maintenance measures. Therefore, optimized maintenance systems for hydropower plant control systems can serve as a component and supplement to fault diagnosis and condition-based maintenance of hydropower turbine generator units. However, as optimized maintenance of the control system, it has its own unique characteristics compared to the unit's own monitoring. [b]3 Basic Functions of Optimized Maintenance Systems[/b] Compared to the unit's condition monitoring and fault diagnosis systems, optimized maintenance systems for control systems share many similarities. Their main functions include condition monitoring, analysis and diagnosis, fault prediction, and maintenance decision-making. The scope of the optimized maintenance decision-making system for control systems extends beyond the control system itself to include its servo systems, such as the electrical control portion of the speed control system and the hydraulic servo system. Control systems are characterized by real-time, dynamic, and continuous control. They are generally closed-loop systems with feedback loops. Because of these characteristics, when control deviations or instability occur, it is difficult to distinguish the influencing factors within the control system, unlike state monitoring and fault diagnosis of generating units, where signal detection, acquisition, and abnormal signal analysis are relatively easy to isolate. Therefore, the use of simulation technology in the optimization and maintenance decision-making system of the control system is essential to identify which link in the control is deviating and gradually narrow down the fault range. Optimization and maintenance is the ultimate goal of this system. Therefore, the system should have the capability to conduct tests on the control system during hydropower plant maintenance and repair, analyze and compare the test data, and optimize control parameters. The system should be able to safely and reliably inject disturbances into the control system for testing, without interfering with the normal operation of the control system when it is put into formal operation. 4 Requirements for Establishing an Optimized Maintenance System for the Control System As the object of the optimized maintenance system, the control system should possess some basic conditions: 1) It should have a microprocessor as its control core and basic information exchange capabilities for reading and inputting data; 2) It should have a relatively rich number of detection points for the optimized maintenance system to collect status data from different parts of the control system; 3) It should have good isolation measures to facilitate the installation of necessary sensors; 4) The core unit should have self-diagnostic capabilities; 5) The control system's servo mechanism should be able to detect its status. [b]5 Establishment of the Optimized Maintenance System for Geheyan Power Plant[/b] The excitation and speed control systems of Geheyan Power Plant are imported equipment, using microprocessors as their control core. They have high reliability and meet the basic conditions for establishing an optimized maintenance system. The power plant's speed control and excitation optimized maintenance systems, as an integral part of the power plant's unit status monitoring and fault diagnosis system, provide sufficient status information and diagnostic analysis information for the unit status monitoring and fault diagnosis system, forming the basis for overall unit fault diagnosis. The optimization and maintenance systems of the excitation and speed control systems at Geheyan Power Plant share many common design principles in terms of system structure and software functionality. The following explanation focuses on the optimization and maintenance system of the excitation system. 5.1 Overall Structure of the Optimization and Maintenance System The structural design of the optimization and maintenance system for the control system must consider the following factors: 1) The changing patterns of the system's information characteristic values ​​during control operation; 2) The occurrence and development process of faults; 3) Various complex application scenarios of the optimization and maintenance system; 4) The system's scalability; 5) Information exchange capabilities. Based on these considerations, the optimization and maintenance system of Geheyan Power Plant adopts the following three-layer structure. As can be clearly seen from the diagram above, the first level mainly completes the acquisition of system operating status signals, parameter settings, and corresponding signals. Since most of the control systems currently operating on-site do not specifically consider information exchange functions with other maintenance systems, and to avoid the control system's control function being affected by frequent data exchange with the optimized maintenance system, the data settings for the control system are all handled through industrial control computer trigger requests. The second level mainly completes the acquisition and analysis of on-site data, performs control system simulation, compares the simulation results with the control output of the control system, and transmits the differences to the maintenance workstation. The third level is an intelligent maintenance decision-making system that receives information from the second level, issues alarms when fault symptoms appear, compares them with historical records, proposes optimized control and maintenance requirements, and records the overall fault situation. 5.2 Simulation Technology in the Optimized Maintenance System Simply monitoring the status of the unit's control system is clearly insufficient; it also requires a testing system with comprehensive functions that closely match actual testing. Simulation technology provides a good technical support platform. The optimized maintenance system's application of simulation technology to the online analysis and control optimization of the control system is a significant innovation. Using such a system, both online simulation monitoring and offline simulation and system testing can be achieved. Ultimately, the optimized maintenance system can be used to change the control system's adjustment parameters based on simulation results and the unit's overall status, achieving the ideal effect of optimized control. 6. Optimized Maintenance System Workstation Design The workstation of this system belongs to the third level of equipment and is also the most important, equivalent to the decision-making body. Its focus is on software structure design, specifically the software composition of the Geheyan Power Plant. The maintenance workstation collects field information in a timely manner, using data management as a link, a knowledge base as the core, and an inference engine as the soul of the system. Based on the control system's operating information and historical status, it activates relevant rules in the knowledge base to derive reasonable explanations for the phenomena and control situations occurring in the control system, providing maintenance strategies. [b]7 Conclusion[/b] The Geheyan Power Plant has made a beneficial attempt at integrated equipment management in terms of control, maintenance, and management. The system's operation has changed our conventional maintenance thinking. Currently, there are still concerns about the operation of the optimized maintenance system and the control system. During the communication process between the two systems, there are doubts about whether the communication service of the control system will be busy, leading to the failure of the control system, and whether the isolation of the detection points is safe. These concerns also affect the overall investment and function of the optimized maintenance system. This is a practical problem that the hydropower industry must face when establishing similar systems. [References] [1] International Symposium on Intelligent Control-Maintenance-Management Integrated System, Wuhan: Huazhong University of Science and Technology, 1998. [2] Fault Detection and Diagnosis Technology of Control System, Beijing: Tsinghua University Press, Zhou Donghua and Sun Youxian. [3] Technical Data of Geheyan Power Plant Control-Maintenance-Management System.