Abstract: With the continuous development of science and technology, the integrated automation system of substations has replaced the traditional secondary system of substations, which has become a development trend of power systems. This article elaborates on the concept of integrated automation system of substations and its application in industrial projects. Keywords: Integrated automation system of substations, application With the continuous development of science and technology, computers have penetrated every corner of the world. The power system has also inevitably entered the era of microcomputer control. The integrated automation system of substations has replaced the traditional secondary system of substations, which has become a current trend in the development of power systems. 1 Concept of Integrated Automation System of Substations The integrated automation system of substations has been gradually accepted by domestic users due to its simplicity, reliability, strong scalability, and good compatibility, and has been successfully applied in some large-scale substation monitoring projects. 1.1 System Concept 1.1.1 System Design Ideas A complete integrated automation system of substations, except for retaining emergency manual operation tripping and closing means in each control and protection unit, can complete all other control, monitoring, measurement, and alarm functions through a computer monitoring system. The substation does not need to set up remote control equipment. The monitoring system fully meets the functions of remote signaling, remote measurement, remote control, and remote adjustment, as well as the needs of unmanned operation. From the perspective of system design, it has the following characteristics: (1) Distributed design. The system adopts a modular, distributed, and open structure. All control and protection functions are distributed in the control and protection units on the switch cabinet or control and protection cabinet as close as possible to the switch. All control, protection, measurement, alarm, and other signals are processed into data signals in the local unit and then transmitted to the monitoring computer in the main control room via fiber optic bus. Each local unit is independent and does not affect each other. (2) Centralized design. The system adopts a modular, centralized cabinet structure. All control and protection functions are concentrated in a dedicated acquisition and control protection cabinet. All control, protection, measurement, alarm, and other signals are processed into data signals in the acquisition and control protection cabinet and then transmitted to the monitoring computer in the main control room via fiber optic bus. (3) Simple and reliable. Since the multi-functional relay replaces the traditional relay, the secondary wiring can be greatly simplified. The distributed design involves wiring between the switch cabinet and the main control room; while the centralized design wiring is also limited to the switch cabinet and the main control room. Its characteristic is that the wiring in the switch cabinet is simple, and the rest of the wiring is completed inside the acquisition and control protection cabinet. (4) Scalability. The system design can take into account the user's future needs for substation scale and functional expansion. (5) Good compatibility. The system consists of standardized hardware and software, and is equipped with standard serial communication interfaces and local I/O interfaces. Users can configure it flexibly according to their own needs, and the system software can also easily adapt to the rapid development of computer technology. 1.1.2 System Specifications The system adopts the most popular industrial standard software, UNIX operating system, X window human-machine interface and TCP/IP network communication protocol. In order to meet the requirements of open system, the system design generally adopts: portable software design - allowing software conversion after the development of hardware technology; standard computer products - allowing the entire system to have high compatibility. 1.2 System Functions The interactive interface between the system and the user is a graphical display window. The standard method of using the mouse to control all function keys allows the operator to perform various operations intuitively. Generally speaking, the system application menu is a tree structure. Users can easily reach each control screen using the menu. Each menu function key has a text description of its purpose and which screen it can reach. Each screen has an alarm display. All system raw data are collected in real time. Each function of the system application can be adapted according to user requirements and system design to meet actual needs, and can be flexibly expanded and modified as the substation is expanded or operated. Under normal circumstances, the system can be configured with the following basic functions: (1) System configuration status; (2) Substation single-line diagram; (3) Alarm table; (4) Event table; (5) Remote control modification of relay setting value; (6) Operation interlock; (7) Power report; (8) Trend chart. 1.2.1 Substation Single-line Diagram The single-line diagram can display the operating status of each control object on the substation system wiring and update it dynamically, for example: (1) The status of the feeder switch, the status of the switch can be distinguished by color. (2) The operation of the switch is selected by the mouse to select the corresponding switch or disconnector. (3) The measurement value of each feeder can be displayed on the same screen. (4) The relay setting value can be modified. 1.2.2 Data Acquisition and Processing: Acquire relevant information, such as switch quantities, measured quantities, and external input signals, and transmit them to the monitoring system for real-time processing, updating the database and display screen, and providing necessary operating information for the system to realize other functions. 1.2.3 Operation Monitoring: The operating status of the system can provide the on-duty personnel with all the necessary information for substation safety monitoring in a timely manner through text, tables, images, sound, or light. (1) Alarms: According to the actual needs of the system, users can specify that alarms will be automatically issued when certain events occur or protection actions are taken. For example, alarms can generally be set to be issued in the following situations: sudden change of switch quantity (such as protection tripping action); circuit breaker position misalignment; analog quantity exceeding the setting value; transformer protection action (such as gas, temperature). The over-limit value of analog quantity can be modified online. Each alarm has time, alarm information, and confirmation status display. (2) Events: All action events in the system, such as relay protection actions, circuit breaker, disconnector, and grounding switch operations. All functions can be automatically printed and stored in the system hard drive. For example, the following events can be recorded: all alarm information; operator confirmation of alarms; switch operations; relay action and status information; system communication status. Each event has a time and related text description, and can be automatically printed. 1.2.4 Relay Setting Values: The protection functions and setting values ​​of each relay can be modified through the system host or centralized control cabinet. All remote modification functions are online, and the modified setting value will be directly transmitted back to the corresponding relay for storage. 1.2.5 Operation Interlocking System: Interlocking functions can be set for all operated objects to prevent operator misoperation. 1.2.6 Analog Input Acquisition and Report Generation: Acquired data is stored on the system hard drive as the basis for report editing. Different reports can be generated based on the actual input signals of the substation: daily, monthly, and yearly reports on active power; daily, monthly, and yearly reports on feeder current. 1.2.7 Trend Charts: Trend charts provide operators with quick and intuitive data statistics. Trend charts can be in graphical or tabular form. 2 Application of Substation Integrated Automation System in Industrial Projects 2.1 Current Status of Domestic Substation Integrated Automation System Domestic substation integrated automation system is not widely used in our institute's design. The main reasons are as follows: (1) Since the client and design institute have long-term experience in the operation, design and maintenance of traditional relay control and protection systems, they generally believe that the old system has high reliability; (2) Domestic substation integrated automation system is not yet popular in China. It is only being tried in some substations in some areas under the strong recommendation of power supply departments in certain regions; (3) Imported substation integrated automation system is expensive. Only some large-scale newly built projects with foreign loans have fully imported this technology and equipment due to the foreign party's requirements for technical level; (4) The quality of operators is not high at present, and they lack understanding of the new system. Due to the above reasons, the development and application of substation integrated automation system in substations are restricted. 2.2 Application Example of Substation Microcomputer Protection Device System In a 35kV substation renovation project in our institute, the domestic substation microcomputer protection device system was successfully applied to the terminal substation. The initial design of the construction drawings adopted traditional electromagnetic relay protection and set up a signal panel. 2.2.1 Comparison between microcomputer protection system and traditional protection system The main difference between the traditional protection system and the microcomputer protection device system is that the traditional electromagnetic relay is replaced by a microcomputer-controlled multi-functional relay, and the traditional signal panel and other devices are eliminated. The corresponding signals are all input to the computer. In order to facilitate centralized control, a centralized design is adopted - all control and protection units are centrally arranged. The structure of the entire substation secondary system is very simple and clear. All equipment consists of microcomputer protection panel, microcomputer acquisition panel, AC/DC panel and monitoring system. The number of panel cabinets is greatly reduced compared with the traditional design. Since all microcomputer devices use network communication to communicate with the local monitoring system instead of the traditional contact output to the signal control panel, the secondary wiring is greatly reduced. At the same time, since the advanced local monitoring system is used to replace the large-area and outdated analog control panel, all operations are safer, more reliable and more convenient. 2.2.2 System configuration and monitoring system of microcomputer protection The system protection consists of the following devices: (1) Line protection device. (2) Main transformer protection device - can complete the main and backup protection of the transformer. (3) Integrated protection device. (4) Line protection device. (5) Capacitor protection device. (6) Backup power automatic transfer device. (7) Small current grounding detection device. (8) Integrated data acquisition device. (9) Basic functions of the monitoring system - data acquisition, control operation, screen production, monitoring display, accident handling, table making and printing. 2.2.3 Issues to be noted when designing a microcomputer protection system (1) Since both the control and protection units use microcomputer devices, some necessary switching quantities and analog quantities should be led from the switch cabinet to the microcomputer acquisition and protection panel. The input quantities are different depending on the control and protection requirements. (2) The terminal wiring between the switch cabinet and the microcomputer device is relatively simple. A large number of secondary wirings are connected in the internal terminals of the microcomputer acquisition control unit and the protection unit. (3) The traditional relay protection setting calculation results cannot be directly input into the computer and must be converted into computer setting values. After the substation was put into operation, except for the initial use of the emergency manual button on the control and protection unit by operators unfamiliar with the microcomputer system, operations were primarily conducted on the microcomputer devices and monitoring computer, and the entire system operated smoothly. 3. Conclusion While the application of substation microcomputer automation systems is not yet widespread, with the continuous development of advanced technology, substation automation systems, with their systematization, standardization, and future-oriented concepts, are gradually replacing the cumbersome and complex traditional control and protection systems.