| With the continuous development of power systems,the total mileage of UHV DC transmission lines is increasing.Due to high line position,long distance and complex terrain of UHV DC transmission,it is more susceptible to lightning disturbance during operation,so its operational stability and Reliability is seriously threatened.Therefore,it is of great significance to study the lightning protection performance of UHV DC transmission lines.Research on the performance of energy resistance mainly focuses on back-striking and shielding failure.However,the factors considered in currentare rearch are not comprehensive.The factors for back-striking lightning performance are mainly the height of towers,the length of insulator,grounding resistance,the amplitude of lightning current,etc;The factors for shielding failure lightning performance are the height of wires,protection angle,ground obliquity,etc.The influence of changes in external insulation of insulator on lightning protection performance has not been considered.In fact,insulators have different surface hydrophobicity,pollution degree,and type of insulators in different environments,and external insulation characteristics are also different.This will lead to change of the lightning protection performance of transmission lines.To study the influencing factors of the lightning protection performance of UHVDC transmission lines,back-striking and shielding failure will be analyzed in this paper.?1?Since the data of impulse flashover voltage of±800kV insulator is less and difficult to obtain through experiments,this paper builds a 110kV composite insulator 3D simulation model based on COMSOL and simulates its impulse flashover voltage.And compared with the impulse voltage obtained in the existing research,used to verify the accuracy of the method;on this basis,the±800kV insulator 3D simulation model is established to simulate the impulse flashover voltage,and compared with the theoretical calculation value;?2?Based on PSCAD,the back-striking simulation model of UHV DC transmission line is established.The model includes transmission line model,insulator flashover model,tower model,grounding resistance model and lightning current model.The simulation model is used to calculate the back-striking lightning withstand level and flashover rate of UHV DC transmission line.and the influence of surface hydrophobicity,pollution degree,and type of insulators of the insulator on the back-striking lightning performance properties is analyzed.?3?Calculate the lightning flashover rate of shielding failure of UHV DC transmission line based on the improved electrical geometry model.When calculating,the influence of working voltage,protection angle,ground inclination and wind speed on the shielding rate are considered.And the influence of surface hydrophobicity,pollution degree,and type of insulators of the insulator on the lightning performance of shielding failure properties is analyzed.The results show that the impulse flashover voltage of the insulator based on COMSOL simulation is 3.7%lower than the experimental data,which is 4.5%and 3.8%lower than the theoretical calculation.The lightning protection performance of UHV DC transmission line decreases with decreasing of surface hydrophobicity of the insulators and enhancing of pollution degree.When the insulator is lost in water and the degree of fouling?ESDD reaches0.20 mg·cm-2,the level of back-striking lightning withstand level is reduced by about 16.2%,and the back-striking flashover rate is increased by about 4 times.The lightning withstand level of shielding failure was reduced by approximately 10.6%and 9.2%,respectively,and the flashover rate of shielding failure was increased by approximately 37.2%and 37.4%.Under the same degree of fouling,the line using the V-type string insulator has the strongest lightning resistance,followed by the line using the type I string insulator,and the line using the type II string insulator is the weakest. |
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