Dynamic Surface Roughness Fouling Simulation And Suspension Correction Model For Porcelain Insulators

Safety problems often occur in the daily operation of indoor substations,and the pollution flashover is one of the problems that threaten the safe operation of power systems.From the perspective of fouling mechanism,the accumulation of fouling particles on the insulator surface is the first step of pollution flashover.Although the enclosure of the indoor substation blocks a large amount of fouling,the possibility of pollution flashover increases due to the existence of the ventilation system and the loss of the natural cleaning conditions of the external wind and rain.Therefore,it is important to investigate the law of insulator surface dirt accumulation to predict the amount of dirt accumulation,so that timely decontamination measures can be taken to reduce the indoor substation pollution flash accident.A new simulation and correction calculation method is proposed for the shortcomings of the current insulator accumulation simulation,i.e.,the obtained insulator surface accumulation shows linear growth and the accumulation saturation process cannot be realized.By establishing a deposition determination model of dynamic surface roughness and a secondary suspension correction model,a prediction of the fouling characteristics that better matches the actual insulator fouling process is achieved.In this paper,the mathematical theoretical model and control equations are determined based on the flow and particle fields involved in the particle deposition process on the insulator surface;the theoretical analysis of the particle collision and adhesion process on the porcelain insulator surface is carried out,and the accumulation process is divided into two phases with different surface roughness,particle-wall collision stage and particle-particle collision stage,by combining with the actual accumulation characteristics.And the particle deposition model with dynamic surface roughness is established from the perspective of energy conservation.The current factors affecting the accumulation amount are mainly wind speed,relative air humidity and particle concentration,which are analyzed by the indoor insulator fouling research and accumulation test.Subsequently,based on wind tunnel fouling tests,numerical simulations were carried out for disk-type XP-160 and double umbrella-type XWP2-160 porcelain insulators,and the particle deposition model with dynamic surface roughness was used for wall boundary conditions.Different growth rates for different accumulation stages were achieved,and the accumulation rate in the particle-particle collision stage was larger than that in the particle-wall collision stage,which was consistent with the experimental results with errors less than 25%and 15%,respectively,which indicated that the particle deposition model was reasonable.In this paper,a secondary suspension correction model based on moment balance is established and applied to the full phase of linear simulation results to realize the saturation phase in insulator accumulation characteristics.The obtained accumulation correction curve shows a trend of gradual flattening with increasing time,and the error of the final accumulation amount and the saturation accumulation amount of the test is less than 10%.Considering that the theoretical secondary suspension correction model is not applicable to the fast-growing phase of accumulation,an improvement is proposed on the basis of the full-phase suspension correction method.Only the linear simulation results of the saturation stage are corrected,and the obtained accumulation curves are more closely matched with the test curves,so the saturation stage suspension correction method is considered reasonable.Finally,the deposition model of dynamic surface roughness is applied to the accumulation test in natural environment through numerical simulation,and the linear simulation results are corrected for suspension in the full phase and saturation phase respectively.The corrected deposition law is in good agreement with the test results,so the insulator deposition characteristic research method in this paper is considered to be applicable to engineering.The three influencing factors of dirt accumulation are reasonably valued and control variables are studied,and we get:the dirt accumulation rate and saturation dirt accumulation on the insulator surface increase with the wind speed within 2～6m/s;the relative humidity of air is within 60%～90%,and the higher the relative humidity,the higher the dirt accumulation rate and saturation dirt accumulation;At particle concentrations of 15 mg/m~3 and 30 mg/m~3,respectively,the accumulation rate is faster for higher particle concentrations,but the saturation accumulation of dirt on the surface of insulator is similar in both concentrations.