Effects Of Atmospheric Pressure On Dry-band Discharge Of Silicone Rubber Insulator

The area of plateau and mountainous in our country takes over 2/3, therefore, more and more polymer insulators have been used in high-altitude area along with the Western Development and the construction of state grid. The polymer insulator has received widespread approval and high praise for its outstanding performance, however, the performance under high-altitude environments needs further investigation and confirmation. Dry-band discharge is considered as one of the main reasons which lead to the aging of polymer insulator, so it is necessary to investigate the characteristics of dry-band discharge under high-altitude environmentsIn this paper, an artificial decompression chamber was established to carry out the experiment under the reduced pressures. Seven different atmospheric pressures from 100kPa to 40kPa were obtained to simulate different altitudes. Two kinds of NaCl solutions with the conductance of 2.5mS/cm and 5.0mS/cm were used to simulate different contamination levels. The test sample was a slice of silicone rubber insulator. The contrast researches about the formation of dry band, the characteristics of leakage current, the discharge characteristics and the frequency characteristics of dry-band discharge have been done under different pressures and contaminations.The main conclusions are as follows: With reducing the pressure, the formation of dry band advanced, however the region of dry band diminished, therefore the cumulative charge of dry-band discharge decreased; Under different conditions, the frequency range of dry-band discharge current was almost the same, mostly around 150Hz; Among the leakage current in dry-band discharge stage, conductive current accounts for 70%, dry-band discharge current accounts for 20% and corona discharge current accounts for 10% under the atmospheric pressure; however the conductive current accounts for 75%, the dry-band discharge current accounts for 15% and the corona discharge current accounts for 10% under the low pressure of 40kPa. With the increase of contamination levels, the formation of dry band advanced, and the cumulative charge of dry-band discharge increased.