Research On Time And Power Signal Phase Synchronization In Wireless Monitoring System Of GIS Partial Discharge

GIS can effectively relieve the situation that resources like land and human are getting shorter and shorter in substation building and operating and so it is widely applied.However,due to its high compactification and isolation,its insulation defects are hard to be found and insulation faults are easy to get larger.So it's necessary to effectively monitor the GIS's status.Compared to the conventional wired monitoring system of GIS,wireless system have simpler structure,easier erection and higher extendibility,and it's able to operate complex calculation and analysis.But at the same time,it has a higher requirement for data synchronization.If the problem of high-accuracy time synchronization and power signal phase synchronization in wireless monitoring system can be solved,the wireless monitoring system of GIS partial discharge can be realized easily,and the operation and maintenance level will be improved.Firstly,this thesis does some research on high-accuracy time synchronization.The node time of wireless network is presented by software and hardware clock and this is basic to the adjustment method of node time.By resolving the transmission routes of wireless messages,the key source of synchronization error is determined.With the above analysis,the time synchronization method of wireless network based on physical layer time capturing is proposed.This method gets time stamps on physical layer and by this way all the uncertain delays above physical layer is removed.After setting up the experimental platform,the response delay of physical layer time capturing is determined.The synchronization accuracy will be further improved by adjust the synchronization according to the response delay.The experimental result shows that this method satisfies the requirement of time synchronization accuracy in GIS wireless monitoring system.Secondly,this thesis does research on power signal phase synchronization.Against the single-phase voltage signal,orthogonal transform is used to construct two orthogonal power signals and forms the phase-frequency detector with dq transform.The loop filter of the Phase-Locked Loop(PLL)is PI controller and the voltage-controlled oscillator is integral segment.The mathematical model of single-phase digital PLL is set up and it's analyzed in theory in three aspects.The parameters of the PLL is also determined.On this basis,a simulation model is set up to verify and analyze the method using Simulink.The simulation result shows that this method satisfies the requirement of GIS wireless monitoring system in the aspects of stability,response speed and anti-interference ability.At last,based on the time and power signal phase synchronization method proposed in this thesis,the software and hardware structure of GIS wireless monitoring system is designed and realized.The monitoring terminals use ultrahigh frequency and acoustic emission sensors and communicate with the background system with WiFi and ZigBee.The background software displays and analyzes the monitoring data.Lab test and field application test are operated to verify the practicability of the system.The test results are perfect as expected and this proves that this system can be widely applied.