| With the in-depth application of the Internet of Things technology in the power grid,intelligence has become the trend of power grid development.State Grid Co.,Ltd.put forward the construction goal of "three types and two networks,world-class".However,due to the different types,standards,and models of many auxiliary equipment in the substation,it is necessary to use a wireless sensor network to carry out unified intelligent control and monitoring of them.Therefore,the construction of the substation wireless sensor network has become one of the key technologies for the grid intelligence.The thesis combines ZigBee wireless sensor network with electronics,wireless communication,radio frequency and other technologies,and designs a wireless sensor network that can be used to connect many auxiliary equipments in substations and intelligently monitor their status.Firstly,ZigBee is chosen as the wireless communication mode in this paper.ZigBee wireless sensor network has the characteristics of low power consumption,low rate,large network capacity and high security.According to TCP/IP Protocol,ZigBee Protocol is divided into five layers: physical layer,media access control layer,network layer,application support sublayer and application layer.Three device types are defined: coordinator,router and end-device.Compared with other wireless communication technologies,ZigBee has a low communication rate,but it consumes the least power,can accommodate the most network nodes,and has a low cost.It is suitable for real-time monitoring system with less data transfer.The working principle of the Z-Stack protocol stack is introduced,and the process of establishing the network of the coordinator and adding the terminal to the network is explained.The electromagnetic environment of substations has a variety of interference to ZigBee wireless sensor network,affecting the transmission stability and reliability,which is a problem to be considered in the design.Secondly,the hardware circuit required for ZigBee wireless sensor network is designed.The system chip selects the CC2530 microcontroller developed by Texas Instruments.When designing schematics in Altium Designer,the schematic package and the PCB package must be consistent.During PCB Layout design,the key circuits such as power module,USB serial port module,Balun circuit module,Crystal Oscillator module are modularized.The isolation of analog and digital circuits should be paid more attention in order to avoiding interference of signals.After the design is finished,the 3D mode is exported for checking,PCB proofing is done without any errors,and then the 0805 SMT device is used for welding.Then transplant the Inverted-F antenna to the hardware circuit required by the ZigBee wireless sensor network.The Inverted-F antenna with small size,simple structure and easy to manufacture has become the choice of ZigBee wireless sensor network.The initial length of the antenna is calculated according to the formula,and then the model is built in HFSS.The resonant frequency,echo impedance,voltage standing wave ratio(VSWR),three-dimensional gain diagram and other parameters are obtained by changing the resonant length of antenna and the thickness of PCB,then the antenna size under the optimal performance was obtained and the actual antenna was made.The VSWR,E-plane and H-plane patterns are obtained by actual measurement.In ADS,the transmission line is simply modeled to match the impedance of the transmission line to the antenna.Finally,the designed ZigBee wireless sensor network is tested.The two nodes can be networked normally,the communication distance between the two nodes is tested,and the data reception success rate at different distances is obtained.The temperature and humidity sensor,abnormal gas detection sensor and infrared detection sensor are connected to the ZigBee wireless sensor network for testing.The status detected by the terminal can be displayed normally on the serial debugging assistant. |
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