Research On Three-Dimensional Reconstruction Technology And Ignition Characteristics Of Secondary Arc Based On Binocular Stereo Vision

UHV transmission lines have the characteristics of long transmission distance,large transmission capacity,low line loss,clean energy consumption,cross-zone energy flexible allocation and consumption,etc.It is an important physical support for the new power system,single-phase automatic reclosing is an important guarantee for the reliable operation of UHV transmission lines,and the existence of the secondary arc will affect the reliable implementation of single-phase automatic reclosing,thus threatening the stability of the power system and the power supply reliability.Therefore,the existence of secondary arcs on the EHV transmission lines should not be ignored,and the study of the electrical characteristics and morphological characteristics of secondary arcs under various operating conditions,revealing the role of different insulator string lengths and secondary arc currents on the ignition characteristics of secondary arcs,to further propose a reliable secondary arc suppression method to improve the stability of the power system is of great significance.Firstly,in order to study the ignition characteristics of the secondary arc in EHV transmission lines in a targeted manner,the insulator string length and the value of secondary arc current under the actual transmission line operating conditions are combined with the characteristics of the real transmission line,and the conditions of the secondary arc generation in the real transmission line are simulated in the test chamber,combined with binocular stereo vision 3D reconstruction technology to simulate the generation of the secondary arc in the air gap near the insulator string,using voltage and current.The voltage and current transformers are used to record the voltage and current waveforms of the secondary arc,supplemented by a binocular high-speed camera,to design a physical simulation and 3D reconstruction test platform for the secondary arc.The platform can flexibly change the length of different insulator strings and the value of the secondary arc current,and can accurately record the voltage and current waveforms during the ignition process,and can obtain binocular images of the evolution of the the secondary arc to record the morphological changes of the secondary arc.The test device can observe and record the evolution of the arc,and can also achieve accurate 3D reconstruction of the arc based on binocular stereo vision technology,so the test platform is fully functional and can meet the research needs.Further,in order to study the change law of various electrical characteristics and typical arc motion behavior characteristics of the secondary arc,this paper observes and records the voltage and current waveforms and motion behavior of the secondary arc under different working conditions,and analyzes the volumetric characteristics,dynamic resistance,arcing time,and typical motion behavior characteristics in combination with the burning process.The results show that the the secondary arc is generated in the air gap ionized by the primary arc,and is influenced by the residual of the primary arc channel,and the burning process can be divided into the stable burning stage and the reignition stage.In the stable burning stage,the air gap has a high temperature and conductivity,the dynamic resistance range of the the secondary arc under different conditions about 40-80 Ω range changes,the secondary arc stable development;with the primary arc channel residual plasma decomposition and air gap temperature decreases,the conductivity of the air gap gradually decreases,the the secondary arc will be temporarily extinguished and reignited on the basis of the last arc channel.In the reignition stage,the air gap is highly ionized,the dynamic resistance of the the secondary arc in the range of 5-10Ω,with the recovery of the air gap insulation when the circuit input energy can not generate a new arc channel,the the secondary arc will be permanently extinguished.In order to quantitatively analyze the change law of arc length,arc diameter and arc surface area during the evolution,this paper grids the three-dimensional point cloud data of the secondary arc,and extracts the accurate data of each characteristic parameter,combined with the combustion process.A preliminary explanation of the mechanism by which different insulator string lengths and secondary arc current values affect the ignition characteristics during the evolution is presented.The results show that:the insulator string length and the value of the secondary arc current will have an impact on the arc length of the secondary arc,the longer the insulator string,the higher the secondary arc current,the longer the arc length of the the secondary arc before the final extinction;the diameter of the the secondary arc changes mainly along the arc length direction and with time,in the arc length direction,the diameter of the the secondary arc gradually decreases along the direction away from the electrode,but the middle part of the diameter is basically the same.In summary,the existence of the the secondary arc can be a threat to the stability of the power system and reliable power supply.The work and results of this paper are important for understanding the evolution mechanism of the secondary arc,and the relevant conclusions can provide reference for the study of the suppression measures of the secondary arc,which is important for improving the operational stability of EHV transmission lines.