Mechanism And Experimental Researches Of Deposition Of Particulate Matters On Conductor Surface

In recent years,due to the long distance between energy and load centers in China,high voltage AC and DC transmission lines across the east,west,north and south of China have developed rapidly.At the same time,due to the complex climate conditions and the serious environmental pollution caused by economic development in China,in recent years,there have been continuous and serious haze weather in most parts of the country.There are a lot of fine particles in fog and haze weather.These fine particles deposited on the surface of high voltage transmission lines will seriously affect the surface morphology of conductors,and then affect the corona discharge and electromagnetic environment of conductors.Based on the accumulation and deposition mechanism of fine particles on the surface of HVDC conductor,the accumulation morphology of fine particles on the surface of conductor under DC nominal electric field was studied by experimental means,and the physical process of formation of accumulation morphology was analyzed by particle motion model.This paper presents an experimental method for the accumulation and corona effect of particulate matter on the surface of DC conductors.Particulate deposition experiments were carried out under the extremely inhomogeneous electric field generated by the coaxial cylindrical electrode structure using a simulated accumulation system for particle generation and separation.For the experimental samples of fine particulate matter deposition,on the one hand,the surface morphology and roughness were observed by scanning electron microscopy and white light interferometer.On the other hand,the corona effect of the experimental samples was measured by the accumulation system,including the synthetic electric field and ion current density.By scanning electron microscopy,we found that the typical morphology of particles on the surface of conductor is "parallel line" in macro view and "multi-particle aggregates" in local view.Then the influence of time and voltage on the morphology is analyzed.It is found that:1.the existence of external electric field is the decisive factor for the deposition of particulate matter on the surface of conductor;2.the increase of time and voltage will promote the agglomeration of particulate matter,on the one hand,lead to the increase of the volume of individual particulate aggregates,on the other hand,lead to the increase of the interval between particulate aggregations.Correspondingly,the roughness of the experimental sample is measured by white-light interferometer.It is found that the increase of time and voltage will lead to the increase of Ra of the surface roughness of the experimental sample.The increase of the surface roughness Ra of the experimental sample also becomes evidence that the corona effect(synthetic electric field and ion current density)of the experimental sample increases with the increase of the experimental voltage Uapp and the experimental time tapp under the same environmental conditions.In order to reveal the mechanism of the typical accumulation morphology,a dynamic model of particle transport and deposition under the coupling action of electric field and force field was established.Based on the calculation space of "volume microelement,dV" on the surface of conductor,by analyzing the force and movement process of particles near the surface of conductor,it is shown that the dielectrophoretic force exerted on particles under extremely inhomogeneous electric field is the cause of the deposition of particles on the surface of conductor,and the dipole interaction between particles promotes the accumulation and formation of "parallel" between particles.The key factors of linear particle chains and particle aggregates.At the same time,through the influence of single particle aggregates on the trajectory of subsequent incoming particles,the effect of the accumulated morphology formed by the precedent on the subsequent particles’ deposition is explained.