Design Of Stray Current Monitor System For The Urban Rail Transit System Based On Zigbee

In DC rail transit systems,the running rails are usually used as the return conductor for traction current. This arrangement mainly focuses on economic considerations,since it does not require the installation of an additional return conductor. The rails along the railway ,which lie exposed on the ground, will easily cause larger stray current. When the train operates in heavy transportation of mass rail transit(MRT)systems, the current required by the train will be quite large up to several thousand amperes and the resistance of the running rail will be about several milliohms to tens of milliohms per kilometer. Therefore, a significant voltage drop on the running rail will be generated. This voltage drop will force parts of the current to leak from the rail and flow into pipework in the earth or steel bars in a strueture.Afterwards,the current leaves the pipe or steel bar and flows through the earth,back into the negative side of the traction substation. This current is known as the stray current or the leakag current. Stray current causes electrical corrosion not only to the structure and piping in MRT systems,but also to adjacent structures and underground piping,including those carrying oil,gas and water.With the advantage of low power consumption,low cost and easy group network, Zigbee is a new global standard for wireless connectivity,having wide foreground of products within home control,building automation and industrial control and monitoring.This thesis analyzed the monitor system of stray current home and abroad and posed a new monitor system of stray current based on wireless network. First, posed a transformer sbstaion monitor system of stray current system design based on Zigbee wireless network. Second,Zigbee studied various communication protocols level of the specific function and role. Used Jennic corporation's JN5139R1 modulewhich conforms to the Zigbee standard and ARM9 as the core,the thesis designed the terminal and coordinator node,showed the whole circuit diagram and completed the debug of the hardware. Then,based on the hardware and opensource linux,the thesis completed the coordinator and the terminal node software design which consist of expiating the embedded system and the node function design.Moreover,the thesis designed the data transfer of USB and the Web server for the transformer sbstaion software design. So the control center can monitor the stray current of the station through the communication channel. The experimental results show that upper computer through the control device can be real-time monitoring the related data of stray current. That is a good practical value.