| Lightning stroke is a major hazard to the reliable operation of power transmissionline. With the transmission line voltage level increase higher and higher, the height oftower on lines is raising. It helps to increase the probability of lightning stroke on thetransmission lines and towers. However, there lack effective ways of the overheadtransmission lines lightning monitoring and reasonable theoretical analysis of theimpulse response of the lightning stroke on the tower. Therefore, it is of greatimportance in scientific significance and engineering application value to provide ascientific basis and guidance for lines and towers defending lightning from the overheadtransmission lines lightning monitoring and an analysis of the transient characteristics atthe lightning stroke on towers.①To monitor transmission line overvoltage and lightning tower current, the paperproposes a set of transmission line overvoltage and lightning tower current onlinemonitoring system. The online monitoring system consists of overvoltage sensor,current sensor, embedded monitoring device and monitoring computer. This paperpresents the basic principle of the overvoltage sensor and has analysis the line-boardmodel of the overvoltage sensor. Using the series-parallel method, the capacitance ofthe high voltage arm of the overvoltage sensor is calculated and the result has beenproved by the simulation and experiment. Meanwhile, the structural of the overvoltagesensor is optimized. The performance and measurement accuracy of the overvoltagesensor has been proved by the experiment. And various influencing factors of theaccuracy of the overvoltage sensor, like interphase coupling, corona, temperature,humidity, pollution, tower, etc are also analyzed. The hardware of the embeddedmonitoring device is of modular design, mainly including four parts: signal conditioningmodule, data acquisition module，monitoring module and wireless communicationmodule. The data acquisition module adopts CPLD as controller chip, achieving dataacquisition with high speed. The monitoring unit adopts high-powered ARM processorto realize data saving and transmission. The compositional structure of all functionmodules are introduced in this paper. At last, the frequency and impulse voltageexperiment has proved that the monitoring system is of better measurement accuracy,the data acquisition function of the embedded monitoring device works regularly, andfast in communication with the monitoring computer. ②For shield failure overvoltage and back flashover recognition, this paperdevelops a set of transmission line current wave online monitoring system formonitoring transmission line current wave. Based on electromagnetic induction, thispower gains induction power from transmission line in high potentials by draw-outpower coil with air-gap and changes transmission line current into stable output voltageby power management unit and charging management unit which supplies power fortransmission line current wave online monitoring system. This paper suggests use frontpart of transmission line current wave as research object because the front part ofcurrent wave can avoid the disturbance of wave reflection. The rise time rate oftransmission current wave is raised to identify the two kind of lightning overvoltageabove. Influencing factors and solutions in application are also considered in this paper.③Considering complicated structure and lack of power supply are key problemsfor the lightning online monitoring system mass popularization, the paper proposes a setof the energy harvesting and online monitoring system for lightning. Signal coil and thepower supply coil would be nested in lightning flow channel. The lightning current willsupply the trigger signal and required energy to the monitoring system to acquire objectsignals, while the polarity and peak value of the lightning current will be stored innon-volatile storage. According to the result of theoretical calculation and simulationanalysis reasonable structure, size, winding turns and other parameters of the signal andthe power supply coil could be obtained. Within the range of10～200kA lightningcurrent, output voltage of signal coil would be linear with the measured lightningcurrent; The signal of the positive and negative polarities lightning current amplitudecould be maintained through the signal conditioning circuit; Through electromagneticinduction, energy could be obtained from the lightning channel by the power supply coil.After the process of overvoltage protection, rectification, charging and voltagestabilization, the energy would be used for the power supply of the lightning currentmonitoring system with suitable time and voltage requirements. According to theexperiment results, this method has been proved to be practical and feasible to measurelightning current accurately with a error below4%, while its power supply enoughenergy to guarantee the normal operation of the monitoring system.④The tower model corresponding to the real circumstances is established toaccurately analyze the wave process at lightning stroke on the tower. This paper takesthe high tower as the object of study and conducts a detailed analysis of the structure ofthe tower by introducing the modular idea in order to report the real situation of the tower in a more authentic and more concrete way. The paper makes the following studyand analysis of the wave process of the lightning striking on the tower: a new towerequivalent impedance modeling method for the tower is put forward in view of therelated theory of electromagnetic field and combining the real structure of the tower.The equivalent impedance of a single vertical conductor is acquired on the basis of thetheory of taper antenna. The equivalent impedance of the vertical four-conductor systemis acquired by introducing compensation factor in consideration of the realcircumstances of the four vertical supports of tower main body. The equivalentimpedance modeling of the cross arm is constructed. The equivalent impedancemodeling of the inclined holder is put up by analyzing the influence of the inclinedholder on the main part of the tower. The functional relationship of the impedance withthe change of the height of the tower by the modularization of the tower is found. TheSZC3tower equivalent impedance model of Zhangjiaba-Changshou is build. Based onthe tower model, this paper analyses the wave process of transmission tower underlightning striking in the ATP simulation software, the distribution condition of voltageon the terminal of cross arm was found, comparing with the simulation result of Haramodel. |
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