Research On Key Issues Of UHV Transmission Lines Secondary Arc Mechanism Analysis

With the rapid development of the economy and the continuous expansion of the size of the power grid,long-distance,large-capacity power transmission has become an inevitable choice for China’s optimal allocation of resources.The development of UHV AC transmission and the construction of a stronger main grid have become one of the key topics for future development of the power grid.Due to the high voltage level and the long transmission distance of UHV lines,the problem of secondary arcs is very prominent.When a single-phase ground fault occurs,if no measures are taken,the secondary power arc will be difficult to extinguish,which will hinder the successful reclosing of the reclosing device.Therefore,this article is based on the research status of secondary arcs in UHV transmission lines under single-phase ground faults at home and abroad,obtain secondary arc images and waveforms through low-voltage simulation experiments,and analyze their morphological and electrical characteristics,so as to study the key issues of secondary arc mechanism analysis.In terms of research on morphological characteristics of secondary arcs,a low-voltage simulation experimental platform for secondary arcs of UHV transmission lines has been established.First,a high-speed optical imaging system using CCD image sensing is used to obtain a secondary arc image.An algorithm for extracting secondary arc is proposed to obtain a contour image of the secondary arc.Identify the irregular motion characteristics of the arc by analyzing the image characteristics of the secondary arc.In addition,by processing the images in the secondary arc motion one by one,the arc length changes,displacement characteristics,and arc column diameter changes during the movement of the secondary arc are also studied;Finally,the comparison of the arc length and the arc column diameter under different secondary currents is performed to analyze the effect of the secondary current on the arc shape.In terms of research on electrical characteristics of secondary arcs,on the basis of the original secondary arc simulation experimental circuit,a parallel reactor equivalent inductance is added to conduct the secondary arc comparative simulation experiment under no compensation,under compensation and over compensation,respectively.The arcing degree,current waveform,voltage waveform,volt-ampere characteristics,and secondary current zero-off time under different compensation methods are analyzed and compared,and the influences of different compensation methods on the arc extinction time,the maximum secondary current,and the maximum value of recovery voltage were compared.In terms of research on arcing time of secondary arcs,based on a series of experimental data related to the arcing time obtained from low-voltage simulation experiments,using the three methods of plotting scatter plots,calculating correlation coefficients and performing multivariate fitting,the effects of the five relevant parameters on the arcing time,including the arc length at the last moment,the arc area at the last moment,the arc diameter at the last moment,the maximum value of the secondary current,and the maximum value of the recovery voltage,are analyzed.Thus,the rule that the arcing time is affected by various parameters is obtained.The research results in this paper can provide theoretical basis and technical support for the in-depth study of the arcing and extinguishing characteristics of secondary arcs in UHV transmission lines.