Effect of Water Droplets on the Corona Discharge Characteristics of Composite Insulators in Arid Areas

摘要

Corona discharge is a common gas discharge phenomenon on the surface of power equipment such as high-voltage transmission lines and insulators. Long-term corona discharge will gradually damage the insulation properties of power equipment, threatening the safe and stable operation of the power system. With the continuous development of China's high-voltage transmission lines, the entire transmission network is spread all over the country. The climate varies greatly in different regions, and the insulators will be in an environment of drought, humidity, ice coating and heavy pollution. The degree of corona discharge will be affected by electric field strength, humidity, contamination and other factors. In extreme operating environments, local corona discharge activity on the insulator surface may increase. The energy generated by the corona discharge and the effect of the electric field force will damage the surface characteristics of the insulating material. Long-term repeated action will accelerate the aging of composite insulators and shorten the service life. Therefore, it is of great theoretical significance and application value to study the corona discharge characteristics of composite insulator surfaces in extreme environments. At present, research on the surface corona discharge of insulators mainly focuses on non-contact detection of abnormal discharge activities caused by factors such as contamination and rainfall. However, there are few studies on the effects of extreme environments on the corona discharge characteristics of insulator surfaces. In this paper, the effects of contaminated water droplets on the surface corona discharge characteristics of composite insulators in arid areas were studied. In arid areas, especially in summer, the air is dry and the temperature difference between day and night is large. After reaching the dew point temperature, the surface of the insulator will easily form morning dew. Surface contamination dissolved in the morning dew will form contaminated water droplets, which will affect corona discharge activity. Long-term corona discharge not only accelerates the aging of the insulating surface material, but also increases the risk of insulator flashover. To this end, this paper built a corona discharge test platform to detect the corona discharge activity on the surface of the insulator. The effects of contaminated water droplets on the corona discharge activity of the composite insulator surface and the corona onset voltage were studied. Firstly, NaCl, CaSO₄and Na₂SO₄were used to simulate the salt contamination in arid areas. The pollution severity was simulated by changing the conductivity. The effect of conductivity of different contamination types on the corona onset voltage was studied. Secondly, by changing the number of contaminated water droplets, the mixing ratio of the three salts, and adding kaolin, the water droplets in the actual operating environment were simulated, and the variation of the corona onset voltage was studied. In addition, the force and deformation of the contaminated water droplets under the influence of the electric field were analyzed. The results show that different types of contamination reduce the corona onset discharge voltage to different extents. The higher the conductivity, the lower the corona onset voltage. By analyzing the characteristic curve between the number of water droplets and the corona onset voltage of the mixed contamination water droplets, it is found that the type and content of the contamination and the number of water droplets will greatly affect the corona discharge activity. The research results of this paper have a certain reference for the design of composite insulators in arid areas.