Corona Discharge Characteristics Of EHV And UHV AC Power Line Under Sandy And Dusty Condition

The construction of EHV and UHV AC power lines in Northwest China has the characteristics of high voltage level,high altitude and frequent sandstorms.Previous studies have mainly focused on the corona measurement of bundle conductors with EHV and below under the conditions of rain,snow,dusty and sandstorms,and some data points have been obtained.However,there is no systematic study on the corona characteristics of AC power lines under sandy and dusty conditions.Sponsored by the National Natural Science Foundation of China(51577069),"Analysis of Corona Loss Characteristic on EHV/UHV AC Power Line under Sandy and Dusty Conditions" and the State Grid Corporation's Science and Technology Project(SGTYHT/15-JS-191),"Corona Characteristics of UHV AC Power Line in High-Altitude Areas under Sandy and Dusty Conditions",this paper focuses on the study of the influence of sandy and dusty parameters on AC power lines in high-altitudes areas.The main contents of the research are as follows:By investigating the meteorological parameters of sandstorms in Northwest China,the indexes of wind speed,dust concentration and particle size were determined.Based on the principle of circular free jet,the sandy and dusty weather simulation system matching the size of UHV corona cage at high altitude was developed.The system can realize the continuous and precise adjustment of dust concentration above 133mg/m3,and has the advantages of small volume and convenient movement.Combining the integrated photoelectric corona-loss monitoring system and UV imager,a set of corona characteristics measuring platform under sandy and dusty conditions at high altitude is established.The corona onset characteristics of AC power lines in high-altitude area under sandy and dusty conditions are studied.The corona onset characteristics of 23 kinds of bundle conductors commonly used from EHV to UHV power lines are measured.The UV discharge patterns and resistive currents under different sandy and dusty parameters are obtained.The experimental values of corona onset gradient under different sandy and dusty parameters are obtained by tangent line method.The effects of subconductor radius,bundle number,elevation,dust concentration and particle size on corona onset gradient are analyzed,and an empirical formula for predicting corona onset gradient under sandy and dusty conditions at high altitude is proposed.The corona loss characteristics of AC power lines under sandy and dusty conditions in high-altitude areas are studied.The corona loss characteristics of 23 kinds of bundle conductors commonly used from EHV to UHV power line are measured,and the corona loss values under different sandy and dusty parameters are obtained.The influence of the sub-conductor radius,bundle number,the field strength,the dust concentration and the particle size on the corona loss is analyzed,and the empirical prediction formula for corona loss under sandy and dusty weather conditions at high altitude is put forward.The corona losses of typical UHV AC double circuit power lines on the same tower under sandy and dusty conditions are evaluated.Based on helical charge simulation method,considering the inhomogeneity of space charge emission and the actual structure of outer strand,the ion mobility measuring results are introduced to simulate the process of space charge emission,migration and recombination.The variation of conductor surface roughness coefficient in the presence of sandy and dusty conditions is further considered.The charging and motion model of dielectric particle in AC ion flow field is established,and a three-dimensional corona loss calculation method for corona cage conductors is established.The 3-D calculation method is applied to calculate the corona loss of single conductor in the small corona cage,conductor with sag in UHV corona cage and even under sandy and dusty conditions.The accuracy of the calculation method is verified.By comparing with the experimental results,it is found that the 3-D calculation model is in good agreement.The physical process of corona discharge can be analyzed more accurately.