Effects of soluble constituents on insulator flashover performance and flashover voltage prediction

Pollution materials affect insulator flashover performance, and there is long-term significance in researching it. In this paper, common kinds of nitrates were used as the soluble pollution, and the ac flashover tests of typical glass insulator were carried out. During the tests, the samples were polluted by dipping method. Also, up-and-down method was used to obtain the insulator flashover gradients under different pollutants and ESDD values. Basing on the test data, the effects of nitrates on insulator flashover performance were analyzed. Research results indicate that, using the current method to calculate the flashover gradient of insulator polluted with nitrates, the relative error will reach 24%; Flashover gradient of insulator under nitrates is higher than that under NaCl; KNO₃ corresponds to lower flashover gradient while Ca(NO₃)₂ corresponds to a higher one; The pollution characteristic b of glass insulator under nitrates is within 0.18 - 0.25; The flashover gradient EL of glass insulator polluted by single or mixed nitrate can be expressed by 25.6×ESDD^-0.21.