| With the continuous development of industry and improvement of voltage level, pollution flashover accidents of power system equipment are becoming more and more serious, which threaten the safe and stable operation of power grid and affect the development of the national economy. Therefore, studying the pollution characteristics of different types of insulators under different climatic and geographical conditions can bring great significance to checking insulation condition and preventing insulator flashover. At present, scholars at home and abroad have studied the characteristics of insulator pollution by natural pollution accumulation tests. However, there are few reports about studying insulator pollution law by using hydrodynamics numerical simulation method. In this paper, a simulation test and a natural pollution accumulation test were adopted to study the pollution characteristics and influence factors of porcelain and composite insulators. This paper is rational and valuable in theory and practice.In this paper, natural pollution accumulation test of insulators from ±660kV Yin-Dong line has been carried out for a year. The laws of contamination depositing uneven character, surface contamination deposit law of insulator shed and dust to salt ratio character have been summarized. Three-dimensional models of U550BP/240H porcelain insulator and FXBZW-±660/300 composite insulator have been built by AutoCAD. Gas-solid two-phase flow modle has been built by using Computational Fluid Dynamics software Fluent integrated in Ansys Workbench. Flow fields and static pressure around insulators have been analysed; Collision coefficient of contaminated particles and insulator surface has been studied. Influnces of wind velocity, particle size, wind angle, electric field on insulator pollution characteristics have been analyzed.Natural contamination test results prove that:the unevenness of contamination between bottom and top surface of composite insulators is much lower than porcelain insulators; The pollution of the high voltage side and the earth side are more serious than the middle part; The smaller the diameter of composite insulator is, the more serious contamination is; The average of dust to salt ratio of both porcelain insulators and composite insulators follow normal distribution law; Dust to salt ratio of porcelain insulators is higher than composite insulators.Numerical simulation results prove that:The static pressure of upwind surface is greater than leeward side. Wind velocity will quickly drop to zero when air is close to the insulator. So, air is easy to form the boundary layer on the surface of insulator, which is conducive to the accumulation of pollution. Collision coefficient between contaminated particles and insulator surface is mainly affected by the synthetical functions of air drag force, gravity and electric field force. Collision coefficient will increase with the increase of wind speed or particle diameter and the influence of particle diameter is more apparent. When the wind angle is upward, the pollution of bottom surface will increase, and the lager the wind angle is, the more serious the pollution of bottom surface will be; When the wind angle is downward, the pollution of top surface will increase. The charged particles are susceptible to electric field force when wind speed and particle diameter are small. When the wind velocity increases, the influence of air drag force will increase and the influence of electric field force will decrease.Field strength distribution characteristics of composite insulator strings have been simulated by finite element method. It has been proved that the distribution of the field strength is consistent with natural pollution characteristics of insulators. Both of them have the feature of "both ends high, intermediate low". It has been revealed that the charged particles are easy to deposite on the surface of insulator with the influnce of electric field force. |
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