I. Introduction
With the development of science and technology, the automation of power grid dispatching has become a trend in the development of power systems. The rapid development of power systems requires a sophisticated, advanced and practical power grid dispatching automation system to ensure. At present, the national adjustment and network, provincial and three-level dispatching systems have been equipped with the power grid dispatching automation system, and the national network is implemented before the system. Now 90% of China's power supply and real-time information of 220kV and above power grids are effectively and accurately collected, and the level of dispatching automation has been significantly improved and improved, especially the reliability and management level of the basic automation equipment of the plant station has been greatly improved, and its accuracy is provided accurately and effectively. The real-time information has become the main basis for dispatchers to carry out grid security and economic dispatch.
The degree of automation of grid dispatching is closely related to the quality and reliability of power supply. To this end, this paper specifically discusses the necessity of power grid dispatching automation and its implementation. This paper discusses the use of GRPS as a means of communication to establish a distribution transformer monitoring system.
The power grid dispatching automation system is based on the actual needs of grid dispatching, and takes the requirements of large-scale grounding system as the design starting point, fully considering the particularity of medium and small systems and centralized control center station systems. The whole system is stable, practical and advanced. Sex and easy maintenance are the main design goals, the configuration is extremely flexible, and the application fields are quite extensive, which can meet the needs of different users. All programs adopt the design of object-oriented method, and the system maintenance and expansion is very convenient.
In the communication of the power grid dispatching automation system, digital radio, GSM short message, and fiber access can be used. The advantage of digital radio is that in addition to the annual frequency fee, there is no additional cost for normal operation; the disadvantage is that it is greatly affected by terrain and climate, resulting in poor reliability and real-time performance of the system. The GSM short message method can realize active reporting; the disadvantage is that the fee is charged according to the bar, the running cost is high, and the delay is quite long when the server of the holiday short message center is busy. Optical fiber communication is stable and reliable, but the construction cost is large, the expansion is poor, and the equipment maintenance is inconvenient. GPRS communication avoids the above problems.
General Packet Radio Service GPRS is a new wireless data transmission service developed on the existing GSM system to provide mobile users with high-speed wireless IP or X.25 services. The theoretical bandwidth of GPRS can reach 171.2Kbit/s, and the actual application bandwidth is about 40-100Kbit/s. The TCP/IP connection is provided on this channel, which can be used for applications such as INTERNET connection and data transmission. GPRS adopts packet switching technology, each user can occupy multiple wireless channels at the same time, and the same wireless channel can be shared by multiple users, and resources are effectively utilized. GPRS allows users to send and receive data in end-to-end packet transfer mode without the need to utilize network resources in circuit switched mode. GPRS is always online, according to the flow rate, thus providing an efficient, low-cost wireless packet data service. It is especially suitable for intermittent, bursty and frequent, point-spread, medium- and small-flow data transmission, and also for occasional large data volume transmission.
Second, the system overview
The development goal of the grid dispatching system is to establish an open platform that is safe and reliable, can provide various advanced services, and provides strong functions for the execution and implementation of the application, and a plurality of relatively independent application subsystems running on the platform. The system is composed of a distributed, open, modular and scalable distribution transformer integrated management system that meets the requirements of modern management of power distribution systems. In addition to providing basic hardware technologies and operating system kernels, the base platform provides basic services such as database systems, information transfer, human-machine interfaces, and real-time environment applications. Application subsystems based on the basic platform include: energy management (EMS), distribution transformer management, line loss management, automatic meter reading, VQC function, harmonic data, power purchase management, data query, automatic report, chart and Interface with other systems, etc. These subsystems implement organic horizontal and vertical integration on the basis of open system architecture (OSA) to form a complete distribution transformer integrated management information system.
The network architecture of the GPRS power grid dispatching automation system is shown in the following figure. The system is divided into three parts, namely the monitoring center master station, the GPRS data transmission terminal, and the monitoring terminal equipment. The main station mainly completes the human-computer interaction work; the network proxy server is mainly responsible for the transparent transfer of the network data link establishment and data transmission and reception; the GPRS data transmission terminal completes the sending and dispatching of the information; the monitoring terminal equipment mainly completes the digital quantity and the analog quantity. collection.
The system central server accesses the enterprise router through the GPRS APN dedicated line, enters the GPRS APN intranet, and obtains a fixed IP address. The monitoring point data does not need to be routed to the Internet network, and the monitoring point DTU also uses the SIM card in the APN. In this way, the point-to-multipoint network is characterized by high security, high stability and good timeliness.
After the GPRS data transmission terminal is powered on, it actively accesses the central GPRS DTU server according to the IP address preset therein, and establishes a TCP/IP link with the monitoring center. The monitoring center main station itself maintains the IP address and ID number of each terminal that is accessed. When the primary station wants to make a data request to a monitoring terminal, it will find the corresponding terminal according to the IP address and ID number. After being sent to the terminal, the terminal sends the data to the network proxy server port through the GRPS data transmission terminal, and forwards the data to the monitoring center main station through the port mapping, that is, a response communication process is completed.
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