The urban distribution network directly faces the majority of power users and is the link between power supply companies and power users. With the continuous development of urban distribution network equipment in my country's power system, the country requires high voltage to directly enter the load center in the construction and transformation of urban and rural power grids, forming a power supply mode of high voltage power receiving-transformer step-down-low voltage power distribution.
1. Brief introduction of urban distribution network
The urban distribution network directly faces the majority of power users and is the link between power supply companies and power users. With the development of social economy and the improvement of people's quality of life, the development scale of urban distribution network is becoming larger and larger, and the network structure is becoming more and more complex. high demands. Facing the competition of market economy, power supply enterprises urgently need to improve their own economic benefits. Conventional, traditional management methods and manual management methods of urban distribution network have been difficult to meet these requirements. While strengthening the planning and construction of urban distribution network, it is necessary to improve the automation level and management level of urban distribution network, improve the reliability and quality of power supply, improve the quality of service to users, and improve the economic benefits of power supply enterprises. It is under this background that the application of computer, communication and network technology and modern management methods to manage the urban distribution network, that is, the distribution management system, has developed rapidly at home and abroad.
2. Facilities and equipment of urban distribution network
Smart box-type substation is the inevitable product of social and economic development and urban construction. In the past 20 years of economic development, the pattern of urban power supply has undergone major changes. In the past, the method of centralized voltage reduction and long-distance power distribution has greatly It restricts the city's power supply and reduces the economic benefits of power supply enterprises. The reason is that the power supply radius is too large, the line loss increases greatly with the increase of power load, and the quality of power supply is also greatly reduced. To reduce line loss and ensure the quality of power supply, the power supply voltage must be increased, which is a well-known fact. For this reason, the country requires high voltage to directly enter the urban area and go deep into the load center in the construction of the urban network. According to data, increasing the power supply voltage from 380V to 10kV can reduce line loss by 60%, reduce total investment and copper consumption by 52%, and its economic benefits are considerable.
At the same time, due to the development of informatization, networking and intelligent residential quarters, not only the box-type substation is required to be safe and reliable, but also the intelligent functions of "four remotes" (telemetry, remote communication, remote adjustment, and remote control) are required. When this kind of intelligent box-type substation is powered by the ring network, with the cooperation of specific independent software, it can complete functions such as automatic positioning of faulty sections, fault removal, load transfer, and network reconstruction, so as to ensure power transmission can be resumed in a short time. It is one of the most economical, affordable, scientific and safe new power distribution devices in today's power distribution system. It integrates high-voltage switchgear, transformers and low-voltage switchgear. It has strong complete sets, small size and compact structure. , high reliability, small on-site installation workload, short installation and commissioning cycle, and mobility, it is an ideal new complete set of equipment in the construction and transformation of urban and rural power grids. Appropriately changing the shape and color of its shell to adapt to the environment can also play a role in beautifying the environment.
3. Planning considerations for urban distribution network
3.1 The urban distribution network planning must be realistic, but also appropriately advanced, and should be forward-looking, reliable and operable.
3.2 Correctly handle the relationship between short-term construction and long-term development, and at the same time consider the comprehensive benefits of society, economy and environment.
3.3 Urban distribution network planning should fully consider the main network planning of 110 kV and above voltage levels, and consider the importance of the 10 kV ring network (outer ring) between 110 kV substations.
3.4 Urban distribution network planning should be approved by the urban construction planning department and included in the overall planning of urban construction in order to be implemented smoothly. The planning should be both authoritative and flexible, and it must be strictly implemented and appropriately adjusted in light of the actual situation.
3.5 At present, there is still a lack of mature experience in the construction of urban distribution network automation, and it can be carried out according to the principle of pilot first and then promotion. General cities can make preparations first, especially the establishment of urban distribution network geographic information management system (GIS), which is not only essential for future urban distribution network automation, but also very useful for current operation management, and can receive immediate results.
4. Demonstration project of urban distribution network
On January 28, 2013, as the only pilot unit of the "Urban Distribution Network Demonstration Project" in the western region, the Chongqing Urban Distribution Network Demonstration Project has passed the acceptance of the State Grid Corporation of China. In the demonstration area, the average power outage time for users dropped from 33 minutes to 4.557 minutes, and for the first time implemented the new project of "closing and switching loads for maintenance lines and bypass systems", truly realizing "zero power outage" for bypass operations.
According to reports, after the Chongqing Urban Distribution Network Demonstration Zone was completed, the power supply reliability rate increased from 99.96% to 99.9915%, the voltage qualification rate increased from 99.629% to 99.875%, comprehensive indicators such as power supply capacity and power supply reliability were fully optimized, and the equipment was healthy. The level has been significantly improved, the line load transfer capacity has been significantly enhanced, and the satisfaction of urban residents with electricity has been greatly improved.