Substation integrated automation utilizes automatic control and computer technology to realize some or all functions of the substation's secondary system. To achieve this goal and meet the requirements of power grid operation for substations, the substation integrated automation system architecture consists of three main components: "data acquisition and control," "relay protection," and "DC power supply system," forming the foundation of substation automation. "Communication Control and Management" acts as a bridge, connecting various parts within the substation and facilitating data exchange between the substation and the dispatch control center. The "Substation Main Computer System" coordinates, manages, and controls the entire integrated automation system, providing operators with various data, wiring diagrams, tables, and other visual displays related to substation operation. This allows operators to remotely control circuit breaker opening and closing operations and provides operators and maintenance personnel with the means to monitor and intervene in the automation system. The "Substation Main Computer System" replaces many simple, repetitive, and tedious tasks previously performed by operators, such as collecting, processing, recording, and statistically analyzing substation operating data and important events occurring during substation operation, such as protection actions and circuit breaker opening and closing. It can also execute various complex tasks according to operator commands or pre-set parameters. "Communication Control and Management" connects all parts of the system, responsible for the transmission of data and commands, and coordinates, manages, and controls this process. Compared with the traditional electromagnetic secondary system of substations, the substation integrated automation system adds two parts in terms of system architecture: "substation main computer system" and "communication control management"; in terms of the specific devices and functions of the secondary system, computerized secondary equipment replaces and simplifies non-computer equipment, and digital processing and logic operations replace analog operations and relay logic; in terms of signal transmission, digital signal transmission replaces voltage and current analog signal transmission. Digitalization makes the substation automation system more accurate in data acquisition, more convenient in transmission, more flexible in processing, more reliable in operation and maintenance, and easier to expand compared with the traditional substation secondary system. The typical structure of the substation integrated automation system is: (1) In low-voltage unmanned substations, the substation main computer system is eliminated or simplified. (2) In actual systems, it is more common to combine some substation automation equipment, such as microcomputer protection and RTU, with electromagnetic equipment (such as analog pointer instruments and central signal system) in the substation secondary system to form a single system. This improves the automation level of the substation's secondary system and enhances the performance of conventional systems, but also requires a greater investment of resources. Substation Integrated Automation Structure Modes The main structure modes of substation integrated automation systems are centralized, centralized-distributed, and decentralized. (I) Centralized Structure: Centralized systems generally use powerful computers with expanded I/O interfaces to centrally collect analog and quantitative information from the substation, perform centralized calculations and processing, and complete functions such as microcomputer monitoring, microcomputer protection, and automatic control. A centralized structure does not mean that only one computer performs all functions such as protection and monitoring. In most centralized structures, the functions of microcomputer protection, microcomputer monitoring, and communication with dispatching are also performed by different microcomputers, but each microcomputer undertakes more tasks. For example, the monitoring unit may be responsible for multiple tasks such as data acquisition, data processing, circuit breaker operation, and human-machine interaction; and for microcomputer protection calculations, one microcomputer may be responsible for the protection of multiple low-voltage lines. The main features of a centralized system are: (1) It can collect various analog and digital quantities of the substation in real time, and complete the functions of data acquisition, real-time monitoring, tabulation, printing, and event sequence recording of the substation. (2) It can complete the protection tasks of the main equipment and incoming and outgoing lines of the substation. (3) It has a compact structure and small size, which can greatly reduce the site area. (4) It has a low cost, especially for 35kV or smaller substations. (5) It is practical. The main disadvantages of a centralized system are: (1) The functions of each computer are relatively concentrated. If one computer fails, the impact is large. Therefore, a dual-machine parallel operation structure must be adopted to improve reliability. (2) The software is complex, the modification workload is large, and the system debugging is cumbersome. (3) The configuration is inflexible. For substations with different main wiring or different scales, the software and hardware must be designed separately, which is a large workload. (4) Centralized protection, compared with the conventional one-to-one protection used for a long time, is not intuitive, does not conform to the habits of operation and maintenance personnel, is inconvenient for debugging and maintenance, and is complicated in program design. It is only suitable for situations where the protection algorithm is relatively simple. Distributed Structure The biggest feature of this system structure is that it distributes the functions of the substation automation system to multiple computers. The distributed mode is generally designed according to function and adopts a master-slave CPU system working mode. The multi-CPU system improves the ability to handle parallel multiple events and solves the bottleneck problem of CPU operation. Data communication between functional modules (usually multiple CPUs) is achieved through network technology or serial method. The selection of a priority network system solves the bottleneck problem of data transmission and improves the real-time performance of the system. The distributed structure facilitates system expansion and maintenance, and local faults do not affect the normal operation of other modules. This mode can form two system configuration structures in terms of installation: centralized panel or hierarchical panel. It is more commonly used in medium and low voltage substations. Distributed (Layered) Structure The distributed structure system logically divides the substation automation system into two layers: the substation layer (station-level measurement and control unit) and the bay layer (bay unit). It can also be divided into three layers, namely the substation layer, the communication layer and the bay layer. The main feature of this system is that it is designed according to the components of the substation and the circuit breaker bay. All the data acquisition, protection and control functions required by a circuit breaker bay of the substation are concentrated by one or several intelligent measurement and control units. The measurement and control units can be placed directly on the circuit breaker cabinet or installed near the circuit breaker bay, and connected to each other by optical fiber or special communication cable. This system represents the trend of modern substation automation technology development, greatly reduces the number of connecting cables, reduces the electromagnetic interference of cable transmission, and has high reliability. It has achieved good results in the fact that some faults do not affect each other, which is convenient for maintenance and expansion. A large amount of field work can be completed at the equipment manufacturer at one time. The main advantages of the distributed structure are: (1) The automation and standardization of the bay-level control unit makes the system more applicable. (2) The unit containing the bay-level function is directly located on the bay of the substation. (3) The logic connection and configuration indication can be controlled by software. (4) It simplifies the configuration of the secondary part of the substation and greatly reduces the area of ​​the control room. (5) It simplifies the interconnection between secondary equipment in the substation, saving a large number of connecting cables. (6) The distributed structure has high reliability, flexible configuration, and convenient maintenance.