Study On Contamination Characteristics Of Insulators On UHVDC Transmission Lines

Flashover accidents of insulator strings running on transmission lines will cause line faults,which will endanger the safe operation of power system.Therefore,the study of the contamination characteristics of the insulator on transmission lines can guide the anti-pollution work,which has important theoretical and practical significance.At present,the measurement of the insulator surface contamination level needs to remove the insulator string from transmission lines and clean it and the operation steps are complex.There is no definite conclusion about the contamination ratio of the insulator under DC and AC voltage type in typical climates of North and South China.It is more convenient to deduce the contamination level of other insulators from the known insulator contamination level.This paper studied the distribution of contaminated particles on the insulator surface by means of theoretical modeling,simulation analysis and experimental testing.Forces acting on contaminated particles were analyzed,and the influence of DC electric field on the movement of contaminated particles was discussed.Because it is difficult to carry out UHV tests in laboratory,so the insulator strings on UHV transmission lines were simplified,and the model consisted with 3 insulator sheds was selected as the research object.It guarantees that the electric field force on contaminated particles around the insulator string in this paper is similar to that around the actual insulator string on UHV transmission line by the analysis of electric field equivalence.And the gas-solid two phase flow simulation model for the study of contamination deposition was established based on the above studies.The deposition and distribution of contaminated particles on the glass insulator string surface under different voltage types were studied.In order to compare with the simulation results of contaminated sediment distribution,an artificial climate chamber was designed and built.The coastal climate of Guangzhou and the inland climate of Zhengzhou were selected as typical climates in North and South China.These two climates were simulated by adjusting the wind speed and humidity in the artificial climate chamber.Contamination tests of the glass and the porcelain insulator model were carried out in the climate chamber.The contamination characteristics on the insulator surface under typical climates in southern and northern regions were compared,and the mechanism of the influence of climate and electrification on the deposition characteristics of contaminated particles on the insulator surface was revealed.The results show that the contamination characteristics of the insulator string obtained from the test is similar to the simulation results.The contamination on the insulator sheds at the both ends of the model is obviously more serious than that on the middle shed,and the contamination on the upper surface is obviously serious than that on the lower surface,and the electric field force acting on the contaminated particles when they move to the lower surface of the insulator shed can overcome its gravity under the action of DC voltage.While under the action of AC voltage,the contamination decreases from the top shed to the bottom shed.According to the test results,the contamination ratio of the insulator under DC and AC voltage types,conversion coefficients of the voltage level and the material to the surface contamination were obtained.In North China,The contamination ratio of the glass insulator under DC and AC voltage type is about 1.51,while that of porcelain insulator is about 1.57.In South China,the contamination ratio of the glass insulator under DC and AC voltage types is about 1.24,while that of porcelain insulator is about 1.39.