Study On The Grade Distribution Of Pollution Zones In Ningxia Power Grid And External Insulation Design Of Overhead Transmission Lines

In the fifties and sixties of the twentieth century, pollution flashover in China power grid only happened in a few industrial provinces near the sea. After the 1970's, pollution flashover accidents had been reported in most of the provinces in China. These accidents firstly occurred in the beginning of the 1990's in Ningxia power grid and the number of the accidents was increasing. Because of adopting many anti-pollution measurements, the pollution flashover accidents had been controlled for a period of time. However, since 2002, along with the rapid industrial development, the pollution flashover became a more and more severe situation. Improving the power grid's ability to resist contamination flashover is a key technical problem to ensure the safe operation of the power system in Ningxia.Basing on the analysis of the mechanism and characteristics of the contamination flashover of the insulators home and abroad, in view of the geographical and meteorological environment of Ningxia power grid, the influences of salt density and dust density on the polluted flashover voltages of various types of insulators is studied in this paper. It is found that the anti-pollution ability of the composite insulator is superior to those of the porcelain insulator and glass insulator. From the research results, division map of the polluted area in Ningxia electric power grid has been plotted, and the method of improving the ability of the equipments to resist contamination flashover instead of clearing the insulator artificially. Because the composite insulator and coating for anti-contamination-flashover (e.g. RTV) are of good ability to resist contamination flashover, they are proposed to be applied in power grid. Meanwhile, Since Ningxia Autonomous Region has a unique climate and different types of industrial pollution, and pollutions in different regions of Ningxia are even different, it is unreasonable to copy the experience of anti-contamination-flashover in other areas. The principles to resist contamination-flashover should be established according to the characteristics of the climate and pollution in different areas as follows: the glass or porcelain insulators in the Shizuishan transmission line, where is serious pollution, dry climate and fog flashover accident-prone areas, should be replaced by composite insulators; the same measurements can be taken in the district of Wuzhong, where the pollution develops rapidly; as to the Guyuan transmission lines, where the region has less pollution and a humid climate, the measurements of increasing the number of insulator, or using insulators of good self-cleaning properties, or coating RTV paint can be taken.