[b]1 Introduction[/b] As a comprehensive power system engineering project, distribution network automation involves many aspects such as urban construction, power grid planning, and equipment selection. The development of distribution automation is based on national conditions, improves the reliability of power supply, and meets the needs of the majority of power users. Its goal is to ensure power supply quality, optimize power grid operation and management, reduce power outage time for users, improve system monitoring and economic dispatch of the power grid, and strengthen planned power consumption and load control to effectively and economically utilize electrical energy [1]. Therefore, the construction of distribution networks should fully consider construction schemes suitable for local conditions, especially how to economically and effectively realize computer management of distribution networks in order to achieve the best economic benefits. Thus, the rational implementation of distribution automation systems has become a very important issue. This paper focuses on the management level issue that must be faced in the implementation of the system scheme, that is, the basic mode of management in the current construction of distribution automation system schemes, which implements management through three communication methods between the three basic layers of the distribution automation system (distribution terminal equipment layer, distribution substation layer, and distribution master station computer management layer) [2]. [b]2 Three Basic Layers of Distribution Automation System[/b] Figure 1 shows the connection diagram of the three basic layers of distribution automation, as well as the system automation connection diagram of exchanging information with the power consumption management system, dispatch automation system, and information management system through the distribution automation computer control system to achieve information sharing and complete comprehensive computer management. [img=350,188]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2002-2/67-1.jpg[/img] The equipment in the distribution terminal equipment layer mainly refers to the primary equipment, operating mechanisms, control terminals, and power supplies of the distribution network. It is the line execution part of the entire distribution automation system and plays a key role in the reliable and safe operation of the distribution network. As the execution mechanism in the power grid field, it must be able to isolate faults and notify the system to realize the basic functions of distribution automation. The distribution substation layer connects the distribution terminal equipment layer and the distribution main system layer, realizes the computer management of the local distribution network, and transmits signals up and down, realizing the intermediate management of distribution terminal equipment information. The distribution automation computer system layer receives and transmits information between distribution terminal equipment, distribution substations, and the main distribution system through the TCM (Transport Control Center) of the substation front-end equipment, and processes the comprehensive information of the entire distribution network through the computer system. [b]3 Three Modes of Distribution Automation System Implementation[/b] Figure 1 shows the conventional communication method between the basic equipment and the main station management of the distribution automation system. In the implementation of the distribution automation system, the connection between these three basic layers can be achieved through three basic modes. Mode 1: A hierarchical management mode in which signals from the outdoor equipment layer are sent to the substation management layer, and then signals from the substation layer are sent to the main distribution dispatching station layer; Mode 2: A relatively centralized management mode in which signals from the outdoor equipment layer and signals from the substation layer are sent to the main station system layer respectively; Mode 3: A relatively independent management mode in which signals from the outdoor equipment layer are sent to the distribution management office of the main station layer, signals from the substation layer are sent to the dispatch management office, and then information is exchanged between the dispatch management office and the distribution management office of the main station layer. 3.1 Hierarchical Management Mode (Mode 1) Figure 2 shows the basic structure of Mode 1. The transmission method of the uplink signal in the figure is as follows: the signal of the outdoor pole-mounted equipment is collected by the RTU and sent to the remote control receiving unit (TCR) of the substation as the first layer of signal management. The integrated management signal in the substation is transmitted to the system control main console (TCM) as the second layer of signal management. Then, the workstation system finally completes the integrated processing of the distribution automation system. The management method of the downlink signal is the opposite of the above. Mode 1 requires a communication channel between TCM and TCR, and between TCR and RTU. [img=312,297]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2002-2/68-1.jpg[/img] 3.2 Centralized Management Mode (Mode 2) Figure 3 shows the basic structure of Mode 2. Uplink signals are respectively from the distribution terminal unit (RTU) and the distribution substation (S/S) signals, each sent to the system control console (TCM) of the distribution master station through its own communication channel, and then sent to the distribution automation system in the workstation for comprehensive processing. Downlink signals are the opposite. Mode 2 requires communication channels between TCM and TCR, and between TCM and RTU. [img=324,234]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2002-2/67-2.jpg[/img] 3.3 Independent Management Mode (Mode 3) Figure 4 shows the basic structure of Mode 3. Signals from the Distribution Terminal Units (RTUs) are directly sent to the system control console (TCM) of the distribution master station for processing by the distribution automation system workstation; signals from the distribution substations (S/S) are sent to the SCADA system of the dispatch automation system, and relevant information between the distribution terminal units and distribution substations is transmitted between the dispatch automation system and the distribution automation system. Mode 3 requires the establishment of a communication channel between the TCM and the RTU, and the distribution automation system exchanges basic data with the SCADA of the S/S through another channel. [img=339,245]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2002-2/67-3.jpg[/img] 3.4 Comparison of the Three Modes Table 1 lists a comparison of the above three modes in terms of system monitoring objects, required communication channels, TCR interfaces, TCM interface support, and overall costs. [img=650,201]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/dwjs/2002-2/69-1.jpg[/img] [b]4 Application Equipment[/b] The main difference in application equipment for power distribution automation systems lies in the selection of power distribution terminal equipment. Different terminal equipment requires corresponding receiving equipment to work together. Afterwards, they share commonalities in connection and processing with the computer system. This article focuses on voltage-type power distribution automation equipment represented by Toshiba's technology and the subsequent equipment used in conjunction with it. 4.1 Power Distribution Terminal Equipment Power distribution automation terminal equipment refers to terminal equipment applied to overhead lines or ground cable networks, including reclosers, automatic distribution switches, ring main units, etc. Communication with the power distribution substation is mainly achieved through RTUs used in conjunction with the terminal equipment. The voltage-type distribution automation terminal equipment, represented by Toshiba's technology and distribution automation products, consists of three devices mounted on the same pole: a vacuum automatic distribution switch, a controller (FDR/RTU), and a power transformer. The primary main equipment uses a VSP5-15JSAT vacuum automatic distribution switch. This product features vacuum arc extinguishing, SF6 gas external insulation, a rated current of 630 A, a rated short-circuit making current of 31.5/40 kA, a dynamic and thermal stability current of 12.5/16 kA (2 s), a mechanical life of 10,000 cycles, an internal isolation break, porcelain-sheathed cable outlet, a maintenance-free design, superior performance, automatic/manual functions, and a distribution automation interface, making it an ideal distribution automation switch. The controller for the distribution switch is mainly used for intelligent fault diagnosis, isolation, and communication. Controllers used in the above-mentioned switch can be divided into two types: fault detection controllers (FDR) and integrated remote control terminal units (RTU). The Fault Detection Controller (FDR) features intelligent on-site fault identification and locking capabilities, enabling automatic isolation of faulty sections and power restoration to non-faulty sections. It also includes a reserved interface for communication, allowing communication between pole-mounted equipment and the substation when paired with a separate communication RTU. The integrated RTU combines intelligent fault detection with communication via a communication line, facilitating connection between the line, pole-mounted equipment, and the substation. The RTU is designed for a transmission speed of 1200 bits/s and uses 1N communication. The switching power supply transformer, as part of the voltage-type equipment, provides power to the switches and controller and provides detection signals to the controller. These three devices constitute the outdoor power distribution terminal equipment. By checking the voltage status and delayed closing coordination, the controller can determine the area where a permanent line fault occurs and lock the switches before and after the fault. Power can only be restored to the affected section when the equipment is reset after the fault is cleared, thus completing the basic functions of feeder automation. 4.2 Distribution Station Equipment The main equipment of the distribution station is the TCR (Transmitter Control Center) used to receive and transmit RTU (Resource Transfer Unit) acquisition signals. The TCR's transmission speed is 1200–9600 b/s, using HDLC-ABM11 communication. The I/O interfaces and their quantities differ for the three modes mentioned above. For mode 1, each cabinet provides 8 channels, managing 480 RTUs, with an I/O capacity of 64 control channels, 224 monitoring channels, and 32 measurement channels. For modes 2 and 3, the I/O capacity is 96 control channels, 256 monitoring channels, and 48 measurement channels. 4.3 Master Station Equipment The front-end equipment for the master station is the remote control console (TCM). Mode 1, each cabinet manages 32 channels of TCR (i.e., manages 15,360 RTUs); Mode 2, each cabinet manages 32 channels, of which 16 are used for TCR and 16 for RTU, for a total of 16 TCRs and 960 RTUs; Mode 3, each cabinet manages 32 channels, for a total of 32 RTUs (i.e., manages 1,960 RTUs). The TCM signal is connected to the EWS through the system bus. The configuration of the computer hardware required for the EWS can be selected according to the size of the system and actual needs. Peripherals such as printers and a console for real-time operation can be configured. Since the background computer equipment and software application have been described in the literature [3-5], they will not be introduced in this paper. [b]5 Conclusion[/b] (1) According to the characteristics of the distribution network, the distribution automation system can be divided into 3 basic layers: distribution terminal equipment layer, distribution substation layer and distribution automation computer control system layer; (2) The management modes connecting the 3 basic layers can be divided into 3 types: hierarchical management mode, centralized management mode and independent management mode. Each of the three models has its own characteristics, and the power sector can choose according to its own characteristics. [b]References:[/b] ［1］ Dong Zhenya. Reflections on several technical hot issues in the construction and transformation of urban power grids [J]. Power Grid Technology, 1999, 23(3): 66-70. ［2］ TOSHIBA Technical Material. Technical information for DAS scheme [S]. KS-Z-CHI-019. ［3］ Kato S, Naito T, et al. Computer-based distribution automation [C]. IEEE Power Industry Computer Application Conference, 1985: 374-380. ［4］ Tong Guofu. Implementation of distribution management system [J]. Power Supply and Utilization, 1998, 15(2). ［5］ TOSHIBA Technical Material. TOSHIBA Distribution SCADA