| In recent years, the pollution flashover accidents in power grid have increased gradually. From 2000 to 2004, the pollution flashover accidents have repeatedly taken place in the major power grid corporation. These accidents may invole in a large area and cause the power system outage for a long time. They have become threat to the safe operation of the electric transmission and transformation equipment and resulted in heavy losses to the national economy. Although the pollution flashover accidents have been inhibited by increasing the creapage distance of the external insulation of the transimission lines in our country, these accidents may still happen because of the deterioration of the atmosphere and environment. Therefore, the further research of the insulator pollution flashover characteristics and putting forward easonable anti-pollution flashover measures are of great significance.This paper sums up the study of pollution flashover at home and abroad, analyzes the hydrophobicity of composite insulator and the discharge on the surface of the water droplet. Considering the anti-pollution measurements used in Ningxia power grid, the following major conclusions can be drawn:①In view of the climate and environment changes and the field operating experiences and the the anti-pollution measurements used in Ningxia power grid, the principles of dividing the polluted zones are determined as follows: the pollution grade is determined by the electronic map of polluted area distribution for Ningxia power system in large-scale area; the pollution grade of the zone in the vicinity of the independent sources of pollution is identified by the nature of the sources and their impact range. On the basis of the division of the polluted area, the revised map of the electronic map of polluted area distribution for Ningxia power system that is in line with the development need of the Ningxia power grid and the implementation details have been obtained.②After the polluted zones has been identified, basing on the pollution grade of the zone, the external insulation configuration level of the power transmission and transformation equipments can be chose. The number and the installation way of the insulator strings and the specific distance of creepage can also be computed out.③To enhance the ability of anti-pollution flashover of the transmission lines, in the process of the improvement of the old lines, the installation way of the composite insulators has been re-designed because of the illogical transmission tower structures. It has been revealed that the pollution flashover voltages are different from each other if their installation ways are different. The pollution flashover voltage of the standard V-shaped composite insulator string is higher than that of the overhang insulator strings by 25%～30%. The V-shaped and A-shaped insulator strings are of good self-cleaning property and are dependent of the tower structure when installing.
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