| Under the influence of micro-topography,micro-meteorology and inclement weather,the ice-covered disasters of transmission lines have occurred frequently in China,significantly affecting the safe operation of the power system.In bad weather,accidents such as broken conductors,broken wires,broken strings of insulators,icing flashover,pollution flashover,and wet snow flashovers may occur,in other serious cases,leading to transmission tower collapse.The application of double string polymer insulators can significantly increase the safety and stability of the operation insulator.In this paper,the optimal suspension of double-string insulator is explored from three aspects: mechanical characteristics,pollution accumulation characteristics and electric field characteristics.According to the operating conditions of the transmission line,the wind load and ice load of the insulator were determined under different wind speeds and ice-covered conditions.To analyze the mechanical characteristics of V-type insulator,a finite element simulation model of double-string insulators was established respectively.The obtained results show that with the increase of wind speed and ice thickness,the mechanical load and maximum deformation displacement of V-type insulators gradually increase.As increasing the inclined angle of the insulator,the axial tension shows the decreasing tendency from 30° to 60° but then the increasing tendency from 60° to 110°.The mechanical characteristics of the V-type insulator are superior to those of the inverted Vtype insulator.Under the same suspension angle,the inverted V-type insulator is subjected to a larger mechanical load than V-type insulator.According to the actual size of the polymer insulator of the large umbrella skirt,the simulation model of the insulator and air flow field is established.Considering the influence of wind speed,air humidity,the concentration of pollution particle,insulator suspension angle and particle size on the particle accumulation characteristics,the flow field distribution around the insulator and the trajectory of pollution particles were calculated.It is found that when the diameter of pollution particles is small,the easier the particles follow the airflow to bypass the insulator surface without colliding with it.However,the collision rate of pollution particles increases significantly with the increase in particle diameter.Under the strong wind velocity,the air swirls are generated on the leeward side of insulator surface,causing the collision rate of the pollution particles increases slowly with the increase in the wind velocity.While the concentration of pollution particle increases,the collision number between insulator surface and pollution particles shows the increasing tendency at different wind velocity.When the particle diameter is in range of 1 μm to 8 μm,with increasing the hanging angle of V-type insulator,the collision rate of pollution particles shows the increasing tendency.When the particle diameter is 9 μm to 50 μm,the collision rate of particles shows the increasing tendency when the insulator angle is lower than 30°,but shows the decreasing tendency from 30° to 60°.As the humidity increases,the water vapor in the air prevents the movement of pollution particles,resulting in the decrease in the collision rate.With increasing the pollution particles diameter,the influence of air humidity on the collision rate of pollution particles is gradually weakened.A 3D simulation model of transmission line,grading ring,double-string polymer insulator and ironware were established.The constant voltage was applied on the transmission line,then the axial electric field distribution,electric field vector distribution and voltage distribution of the insulator under different suspension modes were obtained.The results show that with the increase of the suspension angle of the double-string insulator,the electric field strength of the high-voltage side of the V-type and inverted Vtype insulators gradually increases,and the electric field strength of the low-voltage side gradually decreases.The electric field strength of inverted V-type insulator is higher than that of V-type insulator at the same angle. |
