Study On External Insulation Characteristics Of Power Trans-Mission And Substation Equipment In Fog And Haze

The rapid economic development will inevitably bring some negative impact on the environment.In recent years,China has a large area of fog and haze weather which will last for a long time.Fog and haze weather does harm to human's health,at the same time its influence on the external insulations of power transmission and transformation equipment can not be ignored.Even if the composite insulators with unique hydrophobicity,flashover accidents will occur frequently when they are exposed to fog and haze for a long time.The insulator flashover accidents which caused by the fog and haze environment have a wide range and a long power failure.And they bring huge losses to the national economy.Therefore,it is of academic significance and practical value to carry out the analysis of the cause of insulator flashover in the fog and haze.In this thesis,the haze composition and its physicochemical properties are analyzed in typical polluted areas of Liaoning.Based on the analysis of these data,the real environment can be simulated in the haze simulation experiment box with the data monitoring system.These pollution experiments have been done with different types of insulators such as pollution accumulation test AC flashover experiment under pure fog condition and haze condition.The flashover paths of composite insulators are recorded by high-speed camera.Finally,the finite element analysis software is used to simulate the electric field on the surface of 10 kV composite insulators with droplet,water film or without droplet.And the variations of electric field distribution on the surface of insulators in different conditions are also be analyzed.According to the simulation of haze pollution experiment,the pollution characteristics of different types of insulators are investigated under two conditions-surface cleanness and accumulated contamination.The results show that haze environment promotes the accumulation of pollutants on the surface of insulators,and the second time pollution of contaminated insulators is more obvious.Upper surface pollution of the insulator is more serious than the lower surface.The greater the environmental humidity is,the faster the pollution accumulates.Under the same condition,the full damp time of composite insulator is 3.5 times of the porcelain insulator.AC flashover test under pure fog condition shows that when the content of mist in the air is low,the conductivity of the mist is not obvious to the flashover voltage of the insulator.With the increase of fog water content,increasing the foggy water conductivity makes obvious effect to the flashover voltage of the insulator.The probability of space breakdown increases significantly to the composite insulator with clean surface after the fog dissipation.Through the comparison and analysis of the experimental data in two conditions,the results show that the probability of arc ignition and flashover is higher in the injection marks of pure composite insulators.But for the dirty surface insulators,the trace has little effect on the flashover.The flashover voltage of composite insulators in haze conditions is lower than in the pure fog conductions.