In this paper

the regional distribution characteristic of the decay-like break fault of composite insulator in China is summarized on the basis of investigating the decay-like break fault of the composite insulator which happened from 2010-2020 in State Grid of Corporation Company in China. The decay-like break fault of the composite insulator is mainly located in the eastern coastal and southern regions of China. According to the statistics

about 90% of faulty insulators are located in areas where the annual rainfall is above 500 mm

and the relative environmental humidity is above 60% before the fault. The Decay-like break may occur at any ambient temperature

but mainly concentrates in the ambient temperature above 20 ℃. Except for ambient temperature and humidity

the distribution of decay -like break fault has no obvious correlation with other such natural factors as terrain

altitude and wind. The operating condition related to the decay-like break fault is voltage level and string type. It is confirmed through electric field calculation that excessive partial electrical filed strength on the high voltage side is not the reason of multiple occurrence of decay-like break of 500 kV composite insulator on V strings

but the important reason that the decay-like break fault is distributed in the line insulator at voltage level of 500 kV.