1. Distribution network automation architecture (1) Basic issues of distribution network automation: Although China's distribution network automation work has entered the pilot implementation stage, there are still many different opinions on distribution network automation. The following is an explanation of the concept, objectives and scope of distribution network automation: a. Concept: Distribution network automation is first of all an integrated automation system. In the online (real-time) state, it can monitor, coordinate and manage the equipment of each link of the distribution network and optimize the operation of the entire distribution network. b. Objectives: Improve power supply reliability, improve power quality and improve operation and management efficiency (economic operation). c. Scope: Mainly based on 10kV trunk feeder automation, covering 400V low voltage distribution substation automation, and extending to the user centralized meter reading system. (2) Distribution network automation architecture: Distribution network automation is a systematic project. A complete distribution network automation system includes four main links: power supply network, remote control system, communication system and master station network. One of the current misconceptions: overemphasizing automation and software functions and ignoring the fundamental needs of the power grid. (3) Technical principles for implementing distribution network automation: a. Reliability Principle: The primary goal of implementing distribution network automation is to improve the power supply reliability of the distribution network. To achieve a highly reliable distribution network automation system, the following principles must be followed: ① Reliable power supply points (dual power supply lines, automatic transfer switch, substation automation). ② Reliable distribution network structure (planning, layout, lines). ③ Reliable equipment (primary intelligent switches, secondary outdoor FTUs, TTUs). ④ Reliable communication system (communication media, equipment). ⑤ Reliable master station system (computer hardware, software, network). b. Decentralization Principle: ① Due to the geographical distribution characteristics of distribution networks, the establishment of distribution network automation systems aims for decentralized functions and risks. Intelligent primary equipment (such as reclosers) should be used to resolve faults locally. For county-level distribution networks, the complexity is not high; improving power supply reliability usually requires only dual power supplies. A recloser scheme is recommended, and an appropriate number of switches should be configured on the 10kV main line to ensure protection coordination. ② In order to further improve the overall system safety and reliability, the main station software functions are distributed. The real-time monitoring function based on SCADA runs independently, the online management function based on GIS (Geographic Information System) runs independently, and the power grid analysis and calculation function runs independently. The kernel (database, microkernel scheduling, etc.) between each function is integrated to ensure reliable, efficient and high-quality information sharing. In the implementation of distribution network automation projects, there is another misconception: replacing SCADA (such as ARCINFO) with GIS and processing graphics in real time increases the computer workload and artificially reduces the system safety and reliability. For overhead networks with the primary goal of improving power supply reliability, SCADA real-time monitoring is the focus to ensure timely processing of information at the main station, and GIS online management is secondary; while for cable networks with the primary goal of operation management, they should be treated differently. 2. Distribution network automation implementation technology (1) Power supply mode and primary equipment: Due to the influence of regional and economic development factors, China's distribution network is divided into urban power grids (large and medium-sized cities) and rural power grids (villages and county towns) in terms of management. Urban power grids are mainly based on cable networks, while rural power grids are mainly based on overhead lines. The power supply mode of a power distribution network is determined by three parts: the power source, the line switching equipment, and the network structure (line connections). Different combinations of power source and network structure configurations create a variety of power supply modes, such as single-source radial power supply, dual (multiple) source backup power supply, dual (multiple) source ring network power supply, and grid power supply. Line switching equipment, such as ring main units, reclosers, sectionalizers, circuit breakers, and load switches, provides power supply coordination solutions with varying functions. Urban cable networks often use ring main units (with load switches, vacuum circuit breakers, SF6 circuit breakers, etc.) as the main equipment for distribution lines, while rural overhead power networks often use reclosers, sectionalizers, circuit breakers, and load switches as the main equipment for distribution lines. Power supply schemes categorized by line switching equipment mainly include: cable ring main unit schemes, overhead recloser schemes, sectionalizer (automatic distribution switch) schemes, circuit breaker schemes, and load switch schemes. Due to space limitations, this article will not delve into a detailed comparison of the advantages and disadvantages of each scheme. The following only addresses a few key issues: ① The primary criterion for evaluating the quality of overhead distribution network automation power supply schemes is power supply reliability, including the outage range, number of outages, outage duration, and restoration time under fault conditions. ② In overhead networks, the recloser scheme has practical and technical advantages: In reality, 80% of overhead line faults are instantaneous faults; using reclosers to isolate instantaneous faults can significantly improve power supply reliability. Due to the inherent dangers of high-voltage electricity, it is desirable to resolve line faults locally and avoid escalation, minimizing human intervention. The recloser has a high degree of intelligence, enabling the power supply network to operate independently, without relying on communication systems or master station systems, while allowing for unified planning and phased implementation. Since faults often occur in low-voltage distribution areas of branch lines, branch lines can be protected in conjunction with mainline reclosers using intelligent sectionalizers. ③ For county-level urban distribution networks characterized by overhead lines and a power supply radius within 5km, a dual-power ring network supply with a three-switch, four-section recloser scheme is recommended. ④ Whether relying on intelligent switching equipment for protection and fault isolation or through communication and master station software for fault isolation, the aim is to simplify the complexity of power grid connection. For general urban and rural power grids, dual-power ring network power supply can fully meet the power supply reliability requirements of users. (2) Remote control system and secondary equipment: The remote control of the distribution automation system mainly realizes the monitoring of line switches and distribution substations (transformers) by FTU and TTU. The reliability functions of the remote control system and equipment mainly include four aspects: protection action, ring network control, remote control, and local manual operation. The main problems of the distribution automation remote control system are the line power supply (instrument and operation power supply) and transmission protocol. Designing a reliable uninterruptible power supply suitable for outdoor environments is a difficult problem to realize distribution automation. Due to the geographical distribution of distribution line equipment, the CDT and POLLING protocols currently used in substations are not suitable for distribution automation systems. The new 101 protocol has been applied to a certain extent. Whether it can be used as the remote control transmission standard for distribution automation is still difficult to evaluate. Currently, the IEC is developing a new transmission protocol standard. (3) Communication Schemes and Equipment: The communication schemes for distribution automation include a broad range of communication, such as communication between the master station and substations, between the master station and field units, between substations and field units, and between substations and field units. The communication scheme of the currently implemented complete distribution automation pilot project system refers to communication between the master station and substations and between the master station and field units. Communication is a key and difficult point in distribution network automation. Different regions and conditions require different communication schemes: fiber optic, power line carrier, wired cable, microwave, spread spectrum, etc. However, in general, adopting a hybrid communication scheme is more in line with practical principles. The communication trunk line (referring to 10kV lines) uses fiber optic (the power supply radius in urban areas is relatively short, and it also has a good performance-price ratio), while the branch lines (referring to low-voltage distribution substations) use other communication methods (determined by the distance from the trunk line and the transmission requirements), and long-distance isolated points use wireless transmission. It should be noted that distribution network automation fiber optic communication usually transmits one data channel with a bandwidth of tens of kilobytes, requiring the use of dedicated optical transceivers. Distribution carrier technology is a distribution network communication technology with great potential, but it has not yet been put into practical use. (4) Main Station Network and Software Functions: The main station functions of distribution network automation include SCADA real-time monitoring, GIS (Geographic Information System) online management, and power grid economic operation analysis. The main station framework should break through the traditional single dispatch automation system C/S mode and adopt a PPC/SB/S integrated architecture to fully reflect the characteristics of a comprehensive integrated system with integrated control of distributed networks. The computer network and software platform technologies should fully reflect functionality and openness, and provide cross-platform interfaces with heterogeneous systems, achieving seamless integration with automation subsystems such as dispatch, load control, MIS, and CIS. Based on the actual needs and development requirements of the power supply bureau, the current distribution automation system should realize the design of distribution (network) dispatch (schedule) integration, with a unified platform in terms of technology, easy maintenance in terms of management (considering the actual difficulties of insufficient automation technical strength, especially in county-level power supply bureaus), and cost savings in terms of economy (including savings in construction funds and maintenance costs). It also lays the foundation for the future informatization of power enterprises. In terms of practice, attention should be paid to the unified consideration of upgrading and transforming existing dispatch automation and building distribution network automation, and the unified consideration of new dispatch automation and building distribution network automation. It should be noted that the integration of monitoring and management in distribution network automation systems is technically reflected in the efficient sharing of information, rather than merely loose networking through data conversion. GIS should be closely integrated with CIS and CRM management, and the design should be distributed and networked, incorporating GPS positioning systems to improve the automation level of power supply maintenance and repair, and provide high-quality services. 3. Implementation Modes To improve the efficiency of distribution network automation systems and reduce technical difficulty, the implementation modes are mainly divided into two categories based on the size of the distribution network: county-level cities and large and medium-sized cities. Small-scale distribution networks such as county-level cities can be centrally managed, with a single distribution network master station and a primary communication network. For large and medium-sized cities, a community-based construction approach, similar to dispatch automation, is adopted, using community equipment groups as units to implement a distribution dispatch system model of "unitized terminals - distributed structure - hierarchical network - functional integration - multi-level control," solving information bottlenecks and improving the overall monitoring/management efficiency of the system. 4. Outstanding problems (1) Outdoor operation: The outdoor operating environment of power distribution line equipment puts forward higher requirements for switch main equipment, remote control equipment, communication terminal equipment, etc., mainly to ensure the temperature, humidity, anti-condensation, anti-aging, and anti-sand indicators. Special considerations are given to the external insulation materials of switches, the design of electronic equipment, and the selection of components. (2) Communication reliability: The power distribution network automation system is mainly responsible for real-time monitoring of the safe and reliable operation of the power distribution network. The power supply reliability of the power grid is determined by the power supply scheme. In the power distribution network with low automation and intelligence of line switches, the performance of the entire system is highly dependent on the main station and communication. The wide geographical distribution of the power distribution network makes the reliability of communication transmission one of the difficulties in building a reliable power distribution network automation. The recloser scheme is adopted for the power supply network, which solves the problem of strong dependence on communication. (3) Power supply: The power supply on the power distribution line is used to provide the working power of the switch and monitoring unit. There are two sources: under normal power supply conditions, the power transformer draws power from the line; when the line loses power, the backup power supply (UPS) is started to provide power. For the large current of the operating switch, the power can be provided by the energy storage and discharge of the large capacitor. The challenge lies in the outdoor operation of uninterruptible power supplies (UPS), especially the impact of high and low temperatures on battery performance.