1. Introduction The functionality and application level of power grid dispatch automation systems (EMS/DMS) at all levels in China have achieved a qualitative leap. While introducing, digesting, and absorbing advanced foreign technologies, several domestic EMS/DMS developers have independently developed systems suitable for China's power grid dispatch operation management and actual production needs, continuously launching EMS/DMS systems tailored to the specific conditions of the country. The CC-2000 power grid dispatch automation system, with its independent intellectual property rights, open-source, object-oriented technology, and event-driven processing, was put into trial operation at the North China Power Grid Dispatch and Command Center in July 1999, replacing the WESDAC-32 energy management system imported from Westinghouse Electric Power Company of the UK. This marked a new stage in the application of the North China Power Grid dispatch automation system. For an EMS system, in terms of its function and role, the Supervisory Control and Data Acquisition (SCADA) function is the most basic and important application. This article, based on the SCADA function application of the CC-2000 power grid dispatch automation system, summarizes some work experiences from the aspects of design and development, operation and maintenance, and practical application to meet production operation needs, for reference by relevant personnel. [b]2. Focus on the basics, combine theory with practice, and strengthen practicality[/b] In order to make the North China Power Grid Dispatch Automation System a true technical means for power grid dispatch operation and management, it is necessary to ensure that real-time information reflecting the power grid operation status can be transmitted to the EMS master station system in a comprehensive, accurate, reliable, and timely manner. The EMS master station computer system processes the collected real-time information quickly, accurately, and flexibly, and uses a series of application software to realize the dispatch and management of power grid operation. The North China Power Grid Dispatch Automation System operation and maintenance professionals have gone through several generations of dispatch automation system operation, maintenance, and production practice, and have gradually summarized and improved the application of the system, accumulated some experience, especially in the practical application of SCADA function. (1) Focus on basic automation to ensure the stable and reliable operation of the data acquisition and processing subsystem. The remote control system is a subsystem of EMS, including all functions and equipment such as the acquisition, processing, transmission, and display of real-time operating status information of power plants and substations within the dispatch range. For many years, the author has adhered to the technical policy of "unifying the selection of remote control equipment as much as possible and ensuring consistency in remote control data transmission protocols," equipping remote control plants (stations) within the grid with mature, reliable equipment and operational experience. Simultaneously, primary/backup remote control channels have been implemented for important plants (stations) and those with suitable conditions, resulting in a robust remote control system for the North China Power Grid. Using real-time remote control data as the basis for grid dispatching and the assessment and management of power generation, supply, and consumption operations has also been a long-standing technical policy of the North China Power Grid. Currently, the EMS master station system achieves 100% coverage of remote control information collection required for grid dispatching (remote control information from directly dispatched power plants and important substations is collected directly, while important information from interconnected adjacent power grids is collected through computer communication). The diligent operation, maintenance, and comprehensive professional management of the system equipment by professionals throughout the network have essentially ensured the comprehensiveness, accuracy, and reliability of the remote control data. The data acquisition and processing subsystem of the EMS/DMS master station system (commonly referred to as the front-end system) is a crucial functional node for collecting and processing telemetry information from various plants (stations). It also acts as the gatekeeper for this information entering the dispatch master station system, or rather, the bottleneck for information exchange. The function and role of the front-end system are paramount. If this functional node fails or operates unreliably, the dispatch master station system will lose its information source, inevitably affecting the normal operation of the EMS/DMS. Therefore, the configuration of the front-end system in the CC-2000 power grid dispatch automation system must prioritize reliability and maintainability. To ensure reliability, in addition to using redundant dual-machine (dual interface boards, dual channel interfaces) configurations for the front-end system (Motorola's MVEM industrial control computer), the interface boards for receiving plant (station) telemetry information, and the channel interfaces, dual MO-DEMs are provided for important plants (stations). These main devices and components are all in a hot-standby state and have automatic/manual switching capabilities. • To promptly grasp the operating status of the front-end system and quickly handle faults and anomalies, a user-friendly and flexible human-machine interface and maintenance methods are provided. The operating status of the main/backup front-end computer, plant (station) RTU, receiving plant (station) main/backup interface board and main/backup remote control channels of each plant (station) can be monitored through the monitoring and maintenance screen. The physical location and logical connection relationship between these devices are vividly described on the monitoring screen. In order to monitor the real-time performance and correctness of remote control data, in various screens such as plant (station) wiring, system power flow, power generation form, voltage form and power supply load, any real-time remote control data is represented by different colors to indicate whether it is good data or bad data. (2) Several successful technical processing applications On the basis of ensuring the stable and reliable operation of the basic functions of SCADA, drawing on past experience and making full use of remote control information resources, the real-time information is scientifically processed, providing convenient and flexible maintenance methods. It solves the problem of serious deviation in statistics and calculations caused by errors in remote control data during the participation of important remote control data in various statistical and calculation processes, and ensures the realization of SCADA functions. • To obtain data from the other end for statistical analysis of inter-provincial power transmission and reception, or to calculate the power supply load of various regions within the network, it is necessary to use the power flow value of one end (calculation point) of the inter-network tie line or regional load boundary line for the corresponding calculation formula. The lack of or error of the power flow value at the calculation point of these important lines will directly affect the relevant important calculation results. To solve this problem, the power flow values ​​at both ends of the line are transmitted to the dispatch master station through the RTUs at both ends of the line. When the power flow value at the calculation point is incorrect or the local RTU is under maintenance or out of service, the power flow value at the other end of the line can be temporarily used as a substitute (only line loss error exists). This ensures the basic correctness and continuity of the statistical and calculation results. While solving this function, the human-machine interface provides convenient and flexible online operation methods. • Multi-data source processing: Due to historical reasons, two RTUs (using both Polling and CDT communication protocols) are installed in some important plants (stations), and channel resources ensure that information from both RTUs is transmitted to the dispatch master station; at the same time, information from these plants (stations) can be collected through provincial/regional dispatch computer communication. Therefore, data from the same plant (station) is collected by different devices and channels and sent to the dispatch master station, resulting in multiple data sources. To fully utilize the multiple data sources from the same plant (station), the aforementioned "data from the counterpart" approach was adopted to ensure that each data point is valuable. To achieve multi-data source processing functionality, in the SCADA database design, two or three source points (corresponding to two or three data sources) are defined in the corresponding database table, and a virtual point (virtual plant/station) is defined to store the correct (or selected) results. The virtual point of the virtual plant/station is used for the plant (station)'s screen display, network topology, advanced application software, etc.; historical data, special calculations, data from the simulation disk, and operational statistics reports all use the virtual point value. For ease of maintenance and flexible operation, the human-machine interface provides a screen for multiple data source values, which can automatically/manually select all data from each data source of the multi-data source plant (station) as well as a single point value, ensuring the accuracy and reliability of these important plant (station) data. • Online modification of telemetry polarity and tele-signaling contact status: For telemetry measurements, while ensuring the accuracy of the measurement value, its polarity must also be correct. Otherwise, the power flow displayed by the EMS system will become chaotic, or serious errors will occur in the related statistical and calculation results. The status values ​​of remote signaling quantities indicate whether a switch is open or closed, thus requiring even higher accuracy and reliability. From a professional technical management perspective, functional departments must specify the positive polarity of remote measurements connected to the RTU; and standardize the contact status of remote signaling quantities, such as "1" for closed and "0" for open. Under normal circumstances, remote data operates in the EMS system according to the specified "remote measurement polarity" and "contact status". However, for infrastructure, renovation, and expansion projects, after the addition, modification, and adjustment of remote data are completed, the "remote measurement polarity" and "contact status" may, due to various reasons, be opposite to the specified values, causing errors in the remote data. The WESDAC-32 energy management system imported from Westinghouse in the UK does not have the function of online modification of "remote measurement polarity" and "contact status," and since construction and professional maintenance personnel have already left the site, offline database modifications are the only option, which is both time-consuming and affects the normal operation of the system. The CC-2000 power grid dispatch automation system adds this function, enabling rapid online modification before notifying relevant bureaus (plants) to resolve the issue on-site. [b]3. Accident Recall Function Plays an Important Role in Power Grid Accident Handling and Analysis[/b] Accident Recall (PDR) is an important function in SCADA applications. This function had not been fully utilized in the original dispatch automation system of the North China Power Grid. In the design and development of the CC-2000 power grid dispatch automation system, drawing on past experience and combining it with practical needs, the practicality of the PDR function was emphasized. This function can comprehensively record and save all real-time information from the SCADA database, with a 5-minute (adjustable time) cycle for the entire data section, plus various changes in telemetry and telecontrol events, for the entire accident process within 1 hour before and after the accident (adjustable time period); it also enables full-scene accident recall and continuous inversion description of the entire accident process. Various accident records can be stored on disk for a long time and can be provided for recall and inversion at any time; simultaneously, data and images from any section of the accident can be copied and printed. The various sections required during an accident are printed and bound using a color laser printer, describing the accident process like a comic book, for leaders and professionals to analyze and review. The human-machine interface provides convenient maintenance screens and flexible operating methods (see Figure 1 for the PDR main control interface). [img=292,450]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2000-2/52-1.jpg[/img] Figure 1 PDR Main The PDR has both automatic and manual start-up modes. In automatic start-up mode, the trigger condition can be any remote signaling fault trip of a switch within the network, any telemetry value exceeding its limit, or a predefined typical event to start the PDR. The scope of the PDR function's recording and recall can be defined as a description of the entire network or a description of a local power grid related to the accident within the network. After the CC-2000 dispatch automation system was put into operation, the North China Power Grid experienced two major incidents on July 20 and 21, 1999: the "720" accident at the Xindian 220kV substation in Shanxi Province and a complete power outage at the Shijingshan Thermal Power Plant in Beijing (4 generating units, each with an installed capacity of 200MW). The "720" accident, in particular (caused by an accident at the Xindian 220kV substation, resulting in the shutdown of 9 generating units totaling 2100MW at the Shentou No. 1 Power Plant, Shentou No. 2 Power Plant, Yangquan Power Plant, and Datong No. 2 Power Plant), had a significant impact on the normal operation of the North China Power Grid. The stable operation of the CC-2000 dispatch automation system provided grid dispatchers with real-time, accurate, and reliable information. In particular, the full utilization of the PDR (Power Distribution Detection) function played an unprecedentedly important role in grid accident analysis. By conducting full-scenario accident replays of the two incidents, detailed historical data was provided for accident analysis and the establishment of typical accident cases. This application of the function received unanimous praise from the leaders of the State Power Corporation and the North China Power Group Corporation, as well as grid dispatchers. [b]4 Conclusion[/b] The dispatching, operation, management, and development of modern power grids increasingly demonstrate that power grid dispatch automation systems are an indispensable and crucial technical means to ensure the safe, economical, and high-quality operation of the power grid. EMS/DMS developers in my country have worked closely with professionals in the operation and maintenance of power grid dispatch automation systems at all levels, and their independently developed EMS/DMS systems have matured and played a significant role in practical production. With the deepening of power market operations, EMS/DMS, as a subsystem of the power market technical support system, will assume and play an even greater role.