How to prevent accidents (especially major accidents) caused by erroneous switching operations in power systems has always been a major problem plaguing the industry. With the rapid development of computer technology, microcomputer-based anti-misoperation interlocking systems, with their unique logical judgment capabilities, will soon play a crucial role. At the same time, as in other industries, computer simulation (or even emulation) training systems have brought the training of electrical operators into a new stage. [b]1 Microcomputer-based Anti-misoperation Interlocking System[/b] The microcomputer-based anti-misoperation interlocking system is a computer monitoring system based on computers and their peripherals, with an intelligent expert system at its core, designed to prevent human error. It consists of the following six parts: a microcomputer, a simulation operation and display screen, a field information acquisition and communication system, a computer key, an electronic interlocking device, intelligent expert system software, and auxiliary equipment such as a power supply, printer, keyboard, and mouse. Its structure is detailed in Figure 1 (the equipment within the dashed box is optional). [img=522,265]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/gddl/gddl2000/0001/image1/t44-1.gif[/img][align=left] Figure 1. Structure of a microcomputer-based anti-misoperation interlocking system. There are no specific classification methods or standards for microcomputer-based anti-misoperation interlocking systems in China, but based on their performance and structural characteristics, they can be divided into the following types: a) According to the on-site information collection and communication method: they can be divided into three types: fixed collector with wired communication, fixed collector with wireless communication, and mobile collector with cordless communication. Each type has its own performance characteristics. Fixed wired data acquisition devices are the most traditional and reliable products, but their installation and maintenance are more demanding, making implementation more difficult compared to existing substations. Fixed wireless data acquisition devices require significant investment in expensive communication equipment and highly skilled maintenance personnel to ensure reliability, but offer advantages such as easy installation and remote control. Mobile data acquisition devices are manually carried and collect data point-by-point from equipment, offering the lowest investment and easiest installation and maintenance, but demanding high levels of technical expertise and manufacturing quality from the manufacturer. b) By interlocking control method: they can be divided into fixed program interlocking and intelligent program interlocking. Fixed program interlocking requires the operator to strictly follow a pre-programmed sequence; otherwise, the operated equipment is locked. While this prevents potential misoperation, it cannot adapt to certain special operations not pre-programmed, limiting the flexibility of on-site operation. Intelligent program interlocking type: Operators can perform typical operations according to pre-programmed procedures, and can also perform flexible operations without violating basic principles in special situations. Its operation logic analysis is controlled by an intelligent expert system stored in the computer key. c) According to the operation process monitoring method, it can be divided into: non-retrospective monitoring type and retrospective monitoring type. Non-retrospective monitoring type can monitor and interlock the steps of on-site operation, but does not provide voice prompts and cannot retrospectively trace the actual operation process. Retrospective monitoring type can monitor and interlock during operation, and provides computer voice prompts during operation. Furthermore, after the operation is completed, the operation process (including attempted operations that were not completed due to being interlocked by the computer key) can be traced from the "black box". [b]2 Basic Functions[/b] Due to the different internal structures of various types of products, their working methods have their own characteristics and functional differences, but their basic working functions are the same. 2.1 Microcomputer The microcomputer is the core of the entire anti-misoperation interlocking system. It stores and runs the program control of the entire process. Its main functions are as follows: a) Receiving and analyzing information from the field and the simulation display screen. Since the actual condition of the operated equipment is the basis for determining the operable procedure, it must accurately read and verify the status of the operated equipment and related facilities before and after each operation, compare it with the simulation operation display screen, and provide prompts for the operator to correct errors, so as to ensure the correctness of the status before the current operation (or the next operation). b) Monitoring the simulation operation process. According to industry regulations, a rehearsal should be conducted on the simulation display screen before electrical switching operations. The microcomputer monitors every step of the simulation operation according to the intelligent expert system or the pre-written typical operation procedure, performs logical judgments, determines whether the operation steps are reasonable, and prompts the operator with error messages so that the operator can correct them. c) Transmitting operation procedure instructions. After the operator finishes the rehearsal operation on the simulation operation display screen, the microcomputer sends the correct operation procedure instructions to the computer key and printer. d) Verification of Operation Process: After completing the operation task on-site, the operator is required to insert the computer key and report the operation process. The computer reads the operation record from the "black box" in the computer key and issues voice or text messages to indicate the legal but unplanned operation items that have been performed, the unauthorized operation items that were attempted but not completed by the computer key, and the planned operation items that were not performed. 2.2 Simulation Operation and Display Screen: The simulation operation and display screen is a device used to allow operators to conduct operation rehearsals and display relevant prompts before actually operating the actual equipment. Generally, it consists of a specially designed screen panel equipped with simulated operation keys representing the "electrical primary wiring diagram" of the actual equipment, corresponding switches and disconnectors, status indicator lights, and a communication port connected to the computer. 2.3 Computer Key: The main function of the computer key is to identify the identity of the operated equipment and open the locking device of the operated equipment that conforms to the prescribed procedure, so as to control the operator's operation process. The high-performance product's computer key also includes a microprocessor and a "black box," featuring intelligent error prevention capabilities. This allows operators to perform legitimate operations outside the pre-defined procedures in emergencies without returning to the main control room for simulations. However, the operator must afterwards report the operation to the microcomputer using the computer key. As mentioned earlier, the microcomputer will track and verify the operation, identifying any legitimate operations outside the pre-defined procedures, any attempted violations stopped by the computer key, and any unexecuted pre-defined operations. 2.4 Information Acquisition and Communication Devices: As mentioned above, there are three structural forms. Their main function is to transmit the equipment status to the microcomputer promptly and accurately, serving as the basis for logical analysis. 2.5 Electronic Locking Devices: The main function of electronic locking devices is to control the opening and closing of the operating mechanisms of the operated equipment. It includes an electronically coded lock and a smart electronic key. To achieve program locking, each operating control point of each device should be equipped with an electronic lock with a unique, fixed electronic code. Since the computer key already stores the prescribed procedure for this operation, when the operator inserts the computer key into the electronic lock of the control point of the operated device, the following effects occur: a) The computer key reads the identification code of the point to determine whether the operation control point is the control point for this step in the predetermined procedure. b) If the comparison confirms that it is correct, the control point is unlocked and the message "Operation is allowed" is displayed; otherwise, the control point is locked, and the message "Step error" and the nature of the error are displayed, until the operator finds the correct control point. c) After this step is completed, the control point is locked and the message "This step has been completed" is displayed, allowing the next operation to proceed. The above three steps are repeated for each step and recorded in the "black box". The operation is completed until all tasks are finished, at which point the message "Operation ended" is displayed. 2.6 Intelligent Expert System The intelligent expert system software is the soul of the entire microcomputer anti-misoperation interlocking system. The structure and performance of various products vary greatly, but one of the most basic functions is state judgment and logical analysis. 2.7 Peripheral Equipment Peripheral equipment includes computer input and output devices such as keyboards, mice, printers, monitors, and audio equipment. It is mainly used by system maintenance personnel for program modification and logic programming, and by operators for task selection and operation ticket printing, enabling human-computer interaction. [b]3 Technical Points[/b] 3.1 System Software Quality Issues a) Functional Completeness The system software must not only meet the logical analysis requirements under normal operating conditions (typical operation), but also adapt to the logical analysis requirements of users under special conditions (such as special operations or emergency operations). b) Rigorousness of Logical Judgments Due to the complexity of power system switching operations, the interlocking logic relationships of anti-misoperation interlocking software are correspondingly complex. For example, while most products can basically achieve logical judgments on electrical "five protections," they are unable to handle the correct logical judgments for switching operations such as "network disconnection" and "ring network," which should be an important issue for the technical upgrade of such products. Furthermore, due to the software itself and the flat software it runs on, certain "logic traps" may occur (for example, WIN'95 had a floating-point operation logic trap, which is said to have been resolved in WIN'98), leading to unpredictable logical judgment errors. Developers must pay close attention to this during software development. 3.2 The reliability of the anti-misoperation interlocking system includes two elements: the reliability of the hardware and the reliability of the software system. a) Hardware reliability includes two aspects: the reliability of performance. Common problems include insufficient resistance to mechanical fatigue, electrical insulation aging, and electrochemical corrosion; the reliability of the hardware's structural design. For example, the problem of "running a program without processing" has occurred in the past, which was caused by insufficient hardware structural design, resulting in the operation steps skipping. This phenomenon is very dangerous and is one of the causes of misoperation in power systems over the decades. b) In addition to considering the rigor of the software's logic, another issue for software system reliability is whether the entire system can operate normally when a part of the system (each file) is accidentally damaged. It is also necessary to design a certain amount of "redundancy" during software development to strengthen the cross-support capabilities between programs during logical operations and analysis. [b]4 Experience[/b] 4.1 Issues to be aware of during installation Lock selection and installation are the most problematic aspects of the installation process. Firstly, there's the selection process. Due to significant differences in equipment types across substations, it's crucial to ensure the locks are compatible with the locked equipment to prevent "empty runs" caused by improper lock selection. For example, a foreign-made high-voltage distribution cabinet has a unique structure, and no standard lock can fit it; ultimately, a custom-designed lock must be developed to fit its specific characteristics. The selection of the lock's installation point is also critical to achieving true interlocking of the operating procedure. For instance, the selection and determination of temporary grounding control points is a challenge encountered by almost all substations. The existing grounding conductor must be modified according to the characteristics of each station to ensure that each device has only one grounding wire insertion point; otherwise, the interlocking device is ineffective. Furthermore, the installation of electrical locks should consider the different wiring principles of the control circuits in each substation to determine the appropriate connection method. The author has also encountered some foreign products where the closing and opening power supplies are independent in their control circuit designs. Therefore, it cannot be connected in the conventional way during installation. In this way, the opening and closing interlocking devices of the same circuit breaker must use different identification codes; otherwise, it may cause misoperation and lead to accidents. 4.2 Issues to be aware of during commissioning While it is important to repeatedly check the correctness of the codes of each control point during commissioning, the author believes that testing the system's interlocking logic is even more important. This is because although the interlocking logic is determined only after repeated verification by the operators and programmers, the possibility and concealment of errors are more dangerous due to its inherent logical complexity and human oversight during the input process. The simplest and most reliable testing method is to have the operators perform arbitrary simulation operations (including a large number of erroneous operations) before commissioning. 4.3 Multi-purpose use By utilizing the simulation and pre-testing function of the microcomputer anti-misoperation interlocking system, operators can frequently conduct simulation training on the simulation operation display screen for routine operation exercises and anti-accident drills. This can rapidly improve the operators' proficiency in various operations and their ability to respond to various accident handling procedures. 5. Conclusion The application technology of substation microcomputer-based anti-misoperation interlocking systems is advancing rapidly. With the development of China's science and technology, various newer and better products will enter the power system in the near future. Researching, applying, and promoting these technologies will be a long-term task for the power system.