1. Overview of Urban Distribution Network Structure Currently, Jining urban area has 7 substations: Shizhong Substation, Dongjiao Substation, Xijiao Substation, Nanjiao Substation, Beijiao Substation, Houpu Substation, and Gaoxin Substation, with 46 10kV main lines. In conjunction with urban network construction, renovation, and standardization efforts, with Shizhong Substation as the center, the entire urban area has achieved multi-point power supply and "hand-in-hand" power supply, conforming to the "N-1" rule and meeting the power supply requirements for hand-in-hand lines in distribution automation. The entire distribution network structure is reasonable, and various power facilities meet standards, laying a solid foundation for the implementation of distribution automation. 2. Scope of Distribution Automation System Implementation "Large-scale operation yields benefits." Adhering to the principles of high starting point, high standards, and high representativeness, our company's distribution automation system covers the entire Jining urban area, including one main station system, 7 substation systems, 118 outdoor pole-mounted switches, 10 switching stations, and feeder automation for 42 overhead lines and 4 ground cable lines. 3. Introduction to Distribution Automation Systems Practice has proven that building an integrated DA (Distribution Automation) and GIS-based DMS (Distribution Management System) system, organically combining online and offline systems, power grid structure and geographic graphics, and power grid information and user information, provides us with a complete, time- and space-integrated modern digital distribution network concept. This system will play a crucial role in distribution dispatching, operation, planning, design, construction, business expansion, emergency repair, marketing, and customer service. It should be the basic model for distribution automation and management in China, and it is also the current development direction of modern distribution management worldwide. It is the most important component of digital power supply companies. Our company's distribution automation system is precisely the aforementioned integrated DA and GIS-based DMS system. Traditionally, DA systems have two modes: voltage-based and current-based. Both modes are theoretically achievable; the main consideration should be the actual conditions of the local area. Current-type switches require DC power for operation, resulting in a large workload for operation and maintenance. Fault handling and network reconstruction heavily rely on communication and backend system support, posing significant risks. The shortened power supply radius and increased number of segments in distribution lines, along with changes in line load conditions, present challenges to coordinating the operating times of switches at each level. Furthermore, the need for switches to interrupt fault current leads to high costs and limited adoption. Based on these reasons and the current state of our city's distribution network, our company has selected a voltage-type DA system. 3.1 Overview The distribution automation equipment uses voltage-type automation equipment developed, designed, and manufactured by Toshiba Corporation of Japan, including: pole-mounted automatic vacuum switches, power transformers, integrated remote control terminal units, and in-station fault indication equipment. The distribution automation system consists of a distribution master station system, a distribution substation system, a series of outdoor measurement and control terminals, and a communication system, enabling comprehensive computer monitoring, control, and management of the distribution network. The distribution master station system, located in the distribution dispatch center, has functions such as distribution SCADA, distribution GIS, distribution simulation, online maintenance, large-screen display, and advanced application analysis. The distribution substation system is distributed throughout the urban substations, responsible for information forwarding and monitoring of outdoor monitoring and control terminals (RTUs, FTUs, TTUs, DTUs, etc.) under the jurisdiction of each substation, and can also forward RTU and protection information within the substation. Outdoor monitoring and control terminals are distributed across various nodes of the extensive distribution network, responsible for collecting and forwarding information from distribution lines, and performing local protection against distribution line faults and telemetry, remote control, and remote signaling functions for distribution lines. 3.2 Distribution Master Station System The distribution master station is the core of the entire distribution automation system. The master station system adopts the TOSCAN-D3000C system with Toshiba technology from Japan, and its hardware and software are designed according to international standards. The equipment of the distribution master station includes servers, workstations, TCMs, and peripherals distributed on a two-layer open LAN network. The servers and workstations are Sun Ultra 60 manufactured by Sun Micros Systems, a UNIX EWS manufacturer. The main functions of the system are: (1) Distribution SCADA function: Distribution SCADA not only includes conventional SCADA functions such as data acquisition (remote signaling, telemetry), alarm, event sequence recording, accident tracing, remote control (remote control), calculation, trend curve, historical data storage and tabulation printing, and event recording, but also functions such as dynamic coloring of lines, geographic wiring and GIS integration. It mainly includes data acquisition, processing, display and control functions. (2) Fault handling function: Automatically finds faults in the distribution network and substation and automatically restores normal power supply to the outage area outside the fault area. When a fault occurs in the distribution network or substation, the fault location and cause are determined based on the status changes of the distribution line switches, protection and pole-mounted switches caused by the fault, and the operators are notified through screen display, alarm sounding, printing, etc. (3) DMS Functions: The Distribution Network Geographic Information System (GIS) is the foundation for building a DMS. It is combined with AM/FM to form an AM/FM/GIS system, which establishes the distribution network graphic data and non-graphic parameters on the basis of geographic graphics, and truly reflects the actual route of the distribution network lines, the geographical location and attributes of power equipment, the attributes of the power users, and other information. It provides a network model with geographic information for monitoring the operation of the distribution network and the operation and management of the power system, supports the development of system application software, and realizes functions such as graphic processing, auxiliary design of line engineering, query statistics, equipment operation ledger management, user repair reporting, and auxiliary design of user business expansion. (4) Interfaces with Other Systems: The distribution automation system has the characteristics of open distribution. The network communication adopts the TCP/IP international standard protocol. Therefore, the system can be directly integrated with other automation systems through LAN or through a bridge. This includes interfaces with the company's MIS system, the power consumption MIS system, the dispatch automation system, and large screen display systems. (5) Advanced application software: including network topology, state estimation, online simulation, load management, power flow calculation, short-circuit current calculation, reliability analysis, operation management, engineering management and other software. (6) Calculation of three major indicators: including distribution network reliability analysis, network loss calculation, voltage qualification rate statistics. 3.3 Distribution substation system (TCR) The distribution substation mainly collects information from RTUs in the substation and various outdoor RTUs (FTU, DTU, TTU, etc.), and performs data collection and forwarding. Since the number of RTUs managed by the distribution substation is large (3 to 5 times that of the substation monitoring system), the design of high reliability and flexible configuration of the distribution substation is essential. The main functions of the distribution substation include: (1) Collection and forwarding of RTU data in the substation. (2) Collection and forwarding of outdoor RTU (including FTU, DTU, TTU, etc.) data. (3) Data preprocessing. (4) Protocol conversion. (5) Local maintenance function. (6) Self-diagnosis function. 3.4 The remote control terminal units (RTUs) of the power distribution terminal equipment are distributed across complex power distribution networks in large numbers, operating in harsh environments. Therefore, the products are required to have high reliability and maintenance-free characteristics. The TOSDAC-D21P11 remote control terminal unit has intelligent fault detection and local isolation functions, and also has remote communication capabilities. The TOSDAC-D21P11 product has a rigorous design, a high degree of industrialization, and a structure that is completely maintenance-free. It adopts a fully sealed gold-plated aviation connector and has superior performance. 3.5 System Communication The system communication adopts a mode of primarily fiber optic communication, supplemented by twisted-pair communication and carrier communication. The information transmission volume between the substation and the main station is large, and the communication rate requirement is high. Fiber optic communication has the characteristics of large capacity, high transmission rate and high reliability. At the same time, the fiber optic double ring network also has the "self-healing" function. Therefore, the main communication channel of the power distribution system automation is designed to be fiber optic communication. The communication data volume between the substation and the terminal is relatively small. According to the actual site and equipment, it is designed as a hybrid mode of fiber optic and twisted pair. For some areas located on the edge of the city, where the line to be erected is long and there is no need for commercial operation in the future, the form of distribution carrier is adopted. 4. The goals of the power distribution automation system are: (1) To complete the functions applicable to the switchgear DTU, pole-mounted switch FTU and some distribution transformer TTU, monitor the operating conditions of power distribution equipment, accurately and timely detect defects, reduce on-site operation by personnel, and improve the safe operation level of the distribution network. (2) To optimize the network operation mode, improve the utilization of equipment, reduce the reserve capacity, reduce the investment in power grid construction and operation and maintenance costs, implement the regional line loss assessment, reduce power loss, and improve the economic efficiency of operation and enterprise economic benefits. (3) Provide auxiliary design for business expansion projects, realize the automatic generation of various statistical reports, and improve work efficiency. (4) Improve power supply reliability, improve power quality, speed up business expansion application, shorten fault repair time, provide scientific basis for power management, improve the quality of service, and establish a good social image. (5) Initially establish the basic software and hardware system platform of the main station system and the distribution substation system, leaving room for system expansion. (6) On the basis of the existing communication network, build an ATM communication network that meets the needs of the power distribution system, and lay the foundation for future participation in socialized information services.