Simulation Research On Electric Field Distribution Along Polluted Insulator In Sand-Dust Region

It is very windy and dusty in northwest of China, sandstorm occurs frequently. The sandstorm has significant impact on the safe operation of the railway. Under the effect of sandstorm the amount of sand deposited on the insulator surface is increased seriously, the work environment of insulator is changed by sand deposited on the insulator surface. Once the work environment of insulator is changed, electric field distribution of insulator is distorted. Flashover accident could happen when the electric field along the surface of insulator is greater than field strength of air breakdown. Therefore, the analysis of electric field distribution along the surface of polluted catenary composite insulator catenary in sand-dust region can provide a reference for the study on insulator flashover mechanism.Currently rod-column post composite insulator is extensively used in catenary, Therefore catenary rod-column post composite insulator of FQBG-25 is selected as the analysis object. The model overlying sand insulator is established in the electrostatic field and the model of the insulator with dry band is established in the quasi-static electric field. The closed area is set reasonablely by the artificial truncation method, this satisfies the condition for finite element analysis to calculate the electric field distribution of insulator. Due to the small geometry of sand and large amount, ordinary computer’s memory is difficult to meet the computational demand, therefore rational simplified models based on the structural characteristics are established. So both the accuracy of the results and save computing time are meet. In this thesis, the software COMSOL Multiphysics based on the finite element is used to analy distortion of electric field along the insulator surface, under two kinds of conditon that sand and dry band on the surface.The results of simulation show that sand grains with different size distort electric field along the surface of insulator differently. Electric field strength is increased with increasing of sand grain size. The electric field is affected obviously by charged sand grains. When the amount of charges taken by sand grains increase, the degree of distortion is increased correspondingly. The degree of distortion of the electric field is affected obviously by the polarity and position of sand grains. On the upper surface of sheds, electric field incereased by negative charged sand grains is heavier than sand grains with positive charge. Conversely, on the lower surface of sheds, electric field incereased by positive charged sand grains is heavier than sand grains with negative charge. Rod pillar cylinder between two sheds has maximum leakage current and dry band is generated easily. The maximum field strength is at dry band on the upper or lower surface of sheds. With the increasing of dry band width, the maximum electric field at the surface of the sheds appears at the ends of the dry band, however, field strength at cylinder is decreased. The amount of dry band has an obvious influence on maximum field strength. With the quantity of the dry band at the upper and lower surfaces of sheds increased, the maximum electric field at the dry band is elevated. However, with the quantity of the dry band at the cylinder, the maximum field strength is decreased.