Setting calculations for 110kV power grid relay protection are a highly complex technical task. It requires extensive and iterative calculations, comparisons, and selections of setting values ​​based on the short-circuit current calculations of the power grid, following specific setting calculation principles. This involves a significant workload. Therefore, freeing setting calculation personnel from tedious calculations has become a goal pursued by many experts, scholars, and technicians. The rapid development of computer technology has provided technical support for achieving this goal. Development of computer-based setting calculations began in the late 1970s. Due to the strong theoretical foundation and mature mathematical models of short-circuit current calculations, computer-based short-circuit current calculations became widespread in the 1980s. Subsequently, based on short-circuit current calculations and using the basic model of the network node method, some setting calculation software was developed. These software programs have achieved some success in applications in some 220kV power grids, but for 110kV power grids, there is still no mature software available. This is mainly due to the standardized structure of power grids at voltage levels of 220kV and above, which allows for the description of corresponding relay protection setting calculations using standardized mathematical methods. However, the structure of 110kV power grids is not standardized, with features such as short-circuit groups, T-connections, and small power sources. Therefore, setting calculations for 110kV power grids involve both deterministic problems described mathematically and numerous issues requiring human experience. To solve these problems, some basic methods of expert systems are used to establish a modifiable rule base. The setter uses these rules based on the specific circumstances of the setting process to establish certain logical relationships. Once these relationships are established, the setting calculations can potentially be completed automatically regardless of changes in other system parameters. Because establishing these logical relationships requires some human intervention, we call this method a quasi-expert system model for computer-based setting calculations. [b]1. Conditions for Setting Calculation[/b] When previous setting calculation software was developed, most of my country's 110kV power grids were still operating as ring networks. These software programs fully considered the impact of the electromagnetic loop between the 220kV power grid and the 110kV ring network on protection setting, thus increasing the complexity of the software and reducing its flexibility. These software programs did not pay enough attention to the problems of non-standard setting, numerous mismatch points, and many unconventional settings in 110kV power grid protection, greatly reducing the practical value of the calculated results. Furthermore, due to limitations of the software development platform, developers paid little attention to the convenience of the human-computer interface, making manual intervention very cumbersome, time-consuming, and labor-intensive, forcing its abandonment. Quasi-expert system mode computer setting calculation can solve the problems encountered when previous software was applied to the 110kV power grid, mainly based on two points: the changes in the 110kV power grid structure and the development of computer technology. 1.1 The formation of a single-source radial structure in the 110kV power grid simplifies setting calculations. With the formation of the 220kV main transmission network, the original 110kV ring network was de-looped, forming a radial, zoned network with 220kV substations as the central power source, greatly simplifying the 110kV power grid structure. The elimination of electromagnetic loops significantly altered the development approach for 110kV power grid setting calculation software. After de-looping, the size of the zoned network was greatly reduced, and the protection coordination relationships between various power components became very simple. If the nodal equation method were still used for setting calculations, it would complicate simple problems and would still fail to address issues related to short-circuit groups, T-connections, and small power sources. The quasi-expert mode summarizes all setting coordination relationships of power components into corresponding rules expressed by calculation formulas (the number and complexity of these rules are greatly reduced due to the absence of electromagnetic loops), and then the setter selects the setting rules for the power components to be set. This mode is simple, intuitive, and allows for effective control over the entire setting calculation process. 1.2 The development of computer technology provides strong technical support for the new model. The earliest development of setting calculation software was around the 1970s and 1980s. The current level of computer hardware and software technology is incomparable to that of that time. At that time, the primary consideration in software development was the software's running speed and data storage capacity, followed by the user interface. However, with the current level of computer technology, for software of this scale, the running speed and data storage capacity can be disregarded. Therefore, the focus should be on a good user interface. The quasi-expert system mode completes the input of parameter data, control of the calculation process, and output of calculation results entirely on the system's graphical interface, greatly reducing the difficulty for users to master the software. It can be used conveniently without training. [b]2. Implementation plan for setting calculation[/b] 2.1 Overall design of the scheme The scheme consists of the following modules: power grid topology drawing module, parameter data input module, short-circuit current calculation module, setting calculation rule module, setting calculation module, and ODBC interface module. As can be seen from Figure 1, the entire setting calculation process is completed under the system's graphical interface, without requiring users to operate on the underlying layers. In the dedicated power grid topology drawing module, once the primary diagram is drawn, the network topology structure is built. Each unit in the structure corresponds one-to-one with each component of the system. This correspondence is completed by the software without manual intervention. The parameter database, short-circuit current database, and rule base are all data sources for setting calculations. Among them, the parameter database and short-circuit current database are closely related to the primary structure of the system. When the primary structure of the system changes, the contents of these two databases are modified accordingly. The setting rule base is completely independent, and its modification and supplementation operations are performed separately. 2.2 Introduction to Functional Modules 2.2.1 Power Grid Topology Drawing Module The power grid topology drawing module is an object-oriented power grid drawing tool that supports full-screen dynamic scaling and screen roaming. It draws the primary network diagram of the system using basic graphic elements (such as lines, circuit breakers, transformers, etc.) as drawing units. Each graphic element forms a network topology structure through definition. It has excellent performance and is easy to operate. In addition to having the general functions of graphic editing software, its biggest feature is that it can seamlessly embed databases and protection setting calculation modules. Therefore, this module effectively serves as the user interface for this system, allowing users to perform database operations and initiate protection setting calculations for lines or transformers directly on the diagram. 2.2.2 Parameter Data Input Module: Parameter data is input onto predefined elements on the system's primary diagram. After computer processing, a parameter database is formed, corresponding one-to-one with the network topology. The parameter data can be printed out on the system's primary diagram. 2.2.3 Short-Circuit Current Calculation Module: Utilizing the established network topology and parameter database, and taking each busbar as a fault point, the module calculates the fault currents for three-phase short circuits, two-phase short circuits, single-phase grounding, and two-phase short-circuit grounding under varying operating modes, forming a short-circuit current database, which can be output and printed in a specific format. 2.2.4 Setting Calculation Rules Module: Focusing on single-source radial networks, the module fully considers the impact of short-circuit groups, T-connections, and small power sources on setting calculations. It summarizes and categorizes various protection setting methods, forming a standardized and formulaic rule base. 2.2.5 The setting calculation module is divided into three parts: setting settings, line protection setting, and component protection setting. The relevant coefficients required for setting calculations, such as sensitivity coefficient, reliability coefficient, coordination coefficient, and setting principles, are entered under the setting settings menu before setting. [b]Line protection setting calculations are performed in three ways:[/b] 1) Fully automatic mode: All setting steps are completed by the computer without manual intervention; 2) Semi-automatic mode: The mismatch point and mismatch parameters are specified manually, and the computer completes the subsequent work; 3) Fully manual mode: All setting steps are performed in a question-and-answer format by the user, and the calculation results of each step are displayed on the screen. Protection settings are all performed on the system network interface. Based on the power components selected by the user on the system's primary diagram, the corresponding protection setting calculation module is directly activated. Calculations are performed by calling the parameter database, short-circuit current database, and rule base. The calculation process can be manually intervened. All calculation results are output in the form of a setting calculation report. 2.2.6 The ODBC interface module tuning calculation is completed on a graphical interface. ODBC (Open Database Connectivity) is used to combine parameter data, short-circuit current data, and network topology parameters to complete the corresponding calculations. 2.3 Features of the Solution This solution has the following features: 1) Simple Mathematical Model: Because a single-source radial network is used as the object of tuning calculation, the mathematical model of the tuning calculation is greatly simplified, thus significantly reducing the complexity of the tuning calculation. 2) User-Friendly Interface: The simple mathematical model gives developers a lot of leeway in choosing a development platform. It does not require high mathematical calculation capabilities from the platform, thus allowing full utilization of excellent commercial software launched in recent years to develop software with an intuitive, simple, and flexible user interface from the user's perspective. 3) Flexible Input/Output Design: Parameter input is entirely completed on the system's graphical interface, completely eliminating the previous method of requiring users to number nodes and create data files, greatly reducing workload. There are two ways to output the calculation results. One is to output them on the screen, which allows the person in charge of setting the system to monitor every step of the setting calculation, which is very beneficial for the auditing of the setting calculation. The second way is to output them in the form of a setting calculation sheet, which can be edited in text format. Since many small set values ​​of microcomputer protection are not the result of calculation, but rather some specific requirements of the operating mode, it is necessary to edit the setting calculation sheet. On the one hand, this makes the calculation sheet more complete, and on the other hand, it is also of certain significance for paperless office. 3. Software Selection 3.1 Software Operating Platform: Chinese Windows 95 Chinese Windows 95 is a 32-bit operating system designed specifically for users in mainland China. Therefore, it has a built-in double-byte Chinese character kernel, which can display Chinese characters without the need for an external Chinese platform, greatly facilitating domestic users. Compared with Windows 3.X and DOS, Windows 95 has the advantages of easy operation, support for preemptive multitasking, and stable operation. 3.2 Database Interface Tool: Microsoft ODBC 2.0 Microsoft ODBC 2.0 is an open database interconnection standard proposed by Microsoft in the early 1990s. It is now technically quite mature, and almost all major database vendors provide corresponding ODBC drivers. The advantage of ODBC is that it frees programmers from worrying about the type, location, and format of the data source they need to access. They only need to call the same API functions to interact with the ODBC interface, and direct interaction with a specific database is handled by ODBC. This greatly reduces the workload of programmers and makes programs more flexible, because when the underlying database changes (e.g., from DBASE to ACCESS), the application can adapt to the new data source without major modifications. 3.3 Database Development Software: Microsoft Access 97 Chinese Version Microsoft Access 97 Chinese version is the latest database development and management software released by Microsoft in 1997. It has many advantages in small database applications. It is a desktop relational database, but it can also be used in the development of client/server database front-end applications. The database it generates consists of only one file, making it very easy to manage. Moreover, its development platform is based on Windows 95, which can fully utilize its stability and multitasking advantages, and provide developers with a good development interface, making it quite easy to operate. It has the following characteristics: (1) Access supports multiple data formats and can import data from FoxPro, Paradox 3.X, Lotus 1-2-3.X, Dbase, Lotus 1-2-3, Microsoft Excel and Betrieve. (2) It provides a complete set of highly distinctive integrated window-style menu development environment. All object properties are expressed in a window style, which greatly reduces the programming language and makes it easy and fast to create, edit and debug an application. (3) Access itself is not an object-oriented database system (OODBMS), but it is an object-oriented development environment. (4) Access introduces the SQL database standard query language, and users may directly embed SQL language in the program, thus making Access a relatively complete relational database system. (5) In Access, Windows API functions can be used, and OLE and DDE are supported. (6) The database security control mechanism in Access is also unmatched by traditional databases. 3.4 Programming Language: Microsoft Visual C++ 5.0 Microsoft Visual C++ 5.0 is Microsoft's latest application development tool. Compared to other similar products (such as Borland C++ 5.0, Watcom C++, etc.), it is more powerful. It supports the development of almost all technical standards on the Windows platform. Its compiler supports incremental compilation, recompiling only the modified parts each time, while leaving other parts unchanged, greatly speeding up the compilation process and shortening development time. In Visual C++ 5.0, the Class Wizard's functionality is greatly enhanced, automatically generating a lot of code for developers, allowing them to focus on the specific functions the program needs to achieve, without wasting time on details. [b]4. Conclusion[/b] Due to some inherent characteristics of the 110 kV power grid, the advanced tool of computers has not been effectively applied in the field of 110 kV power grid setting calculation. Based on the changes in power grid structure and the development of computer technology in recent years, this paper proposes a new scheme for computer-based setting calculation of the 110 kV power grid. This scheme has the characteristics of simple mathematical model, user-friendly human-computer interface, and flexible input and output, and has strong operability. In the future, with the development of computer technology, more artificial intelligence technologies will be introduced to further improve the automation level of software.