Ionic Wind Flow Characteristics Of Negative Corona Discharge In DC Transmission Conductors

Under the strategic guidance of the"dual carbon"goal,new energy in our country is booming,but space transmission and consumption have become the bottleneck.It is imminent to build a new energy infrastructure network,and the strategic position of UHV as the backbone of power transmission has begun to be highlighted.However,with the improvement of the voltage level of transmission lines,the problem of corona discharge has attracted more and more attention.Most of researches on corona discharge focus on the electromagnetic environment and discharge characteristics,and the research on ionic wind is also focused on the engineering application.Nonetheless,there are few studies on the influence of ionic wind induced by corona discharge in transmission lines on the flow field and corona vibration during the incoming flow.Therefore,it is of great significance to study the flow characteristics of ionic wind induced by corona discharge in conductors for analyzing the causes of corona vibration,preventing,controlling corona vibration and improving the mechanism of corona vibration.In this thesis,COMSOL Multiphysics software was used to simulate the phenomenon of corona-induced ionic wind in transmission conductors.Firstly,the surface state of the conductor was characterized by experimental methods,and then the influence of the corona ionic wind on the smooth circular cross-section conductor on the surrounding flow field was studied by using the"wire-plate"electrode.Then,according to the experimental results,the discharge of the rough conductor was simulated.Finally,the discharge,flow and EHD force characteristics of corona-induced ionic wind with smooth circular cross-section,rough circular cross-section and real cross-section shape were studied.The specific research contents are as follows:(1)Taking ACSR as the research object,the surface profile of the conductor after different damages was extracted by the light-section method,and the image was processed to obtain the surface roughness of the conductor,which was compared with the surface roughness of the conductor measured by the roughness profiler.The applicability of the two indicators to characterize the surface roughness of the conductor in the numerical model was discussed.The results show that R_a can characterize the surface roughness of the conductor more accurately in engineering practice,but in the numerical simulation,it is more advantageous to use R_z to characterize the surface roughness of the conductor to study the influence of the roughness value on the ionic wind effect.(2)A two-dimensional monopole ionic drift model coupled with the Navier-Stokes equation was developed using an electro-hydrodynamic approach to elucidate the mechanism of ionic wind generation by corona discharge.The corona-induced ionic wind flow characteristics of smooth and rough circular cross-section conductors were studied,mainly including voltage level,conductor diameter,surface roughness on the discharge characteristics,ion wind flow field distribution,current body force and the effect on the incoming flow rate.The results show that the cross-sectional area and surface roughness of the wire around the discharge characteristics and flow characteristics of the significant impact of structural changes to promote the discharge,inhibit the effect was obvious,while the wire surface EHD force distribution with the same ion density distribution,the voltage level was linearly related to its size.(3)A corona-induced ionic wind model of a real conductor cross-section with incoming flow was established to study the corona characteristics and flow properties of corona discharge in steel-core aluminum stranded conductor cross-sections.The effects of voltage level and number of outermost strands on discharge characteristics,current force,ion wind combined current field and combined velocity size were analyzed.The results show that as the number of outermost strands of the conductor increased,the discharge point increased and the ionic wind effect was significantly enhanced.The research in this paper would help to understand the mechanism of corona discharge ionic wind generation in transmission lines and provided theoretical guidance for suppressing corona vibration characteristics,perfecting corona vibration mechanism and conductor selection for high-voltage lines.