The Development Of Substation Monitoring System Based On ARM

In recent years,the smart grid has been vigorously developed in China.The transformer substation which has new type of intelligent equipments is an important part of the smart grid.The economical and reliable substation monitoring system is vital to ensure the stable operation of the intelligent substation.The traditional substation monitoring system with the wired data transmission has some disadvantages,such as wiring cumbersome,poor flexibility,aging and so on.Some environmental monitoring systems which use wireless data transmission,such as Bluetooth,Wifi and so forth,which have the disadvantages of high cost and large power consumption.Besides,traditional video monitoring system for substation has the problems of low coding efficiency and low performance-to-price ratio.In order to solve these problems,a set of substation monitoring system is designed and built in this dissertation,which takes the new type of arm processor of Exynos4412 as the core and combines the ZigBee wireless sensor network technology and video compression coding technology,meanwhile,the CSMA/CA has been improved,which as the core algorithm in MAC layer for ZigBee.The main work can be expressed as follows:Firstly,the development process of substation monitoring system and the research progress at home and abroad are introduced.The main technologies involved in the substation monitoring system are introduced and analyzed,including Zigbee,embedded web server technology,H.264 video format and video coding technology.Then,the substation monitoring system is designed and built,which is based on ARM platform and ZigBee technology.The monitoring information of the system includes environment and video.The environmental monitoring system collects and transfers the environmental information which includes temperature and humidity of substation by ZigBee network unit,and the data is transmitted to the ARM processor through the serial port.The ARM processor transfers the data through the TCP/IP network to the upper computer,and the information is displayed on the host computer in the form of a web page.The video monitoring system collects video information by the structure of USB camera and ARM processor.The video information is coded by H.264 standard and saved,meanwhile,the encoded file will be transmitted to the host computer by RTP protocol.The upper computer can display the video data in real time through the VLC player.Finally,the substation monitoring system is tested.The results of test verify the feasibility of the system.Besides,the CSMA/CA is the core algorithm in MAC layer for ZigBee,which can't provide priority service for the system of substation monitoring and has poor performance in high load network.In this dissertation,a new scheme is proposed,including that the priorities of different services can be rated by setting the contention window according to network load states.Meanwhile,the backoff exponent of the algorithm can be adjusted with network load.The network model of the proposed algorithm is constructed by means of Markov chain model and is simulated by NS2.The simulation results show that the network throughput capacity is improved and the packet loss rate is reduced,obviously,the overall performance of the network is optimized with a little time delay increasing.