Failure Analysis of “Lantern-Like” Composite Insulator Heating Defects and the Improved Dye Penetration Test Method

In 2019, 27 new 500 kV AC composite insulators showed a severe heating, different from the traditional heating failure reported in recent years, the heating area isn’t limited in the high voltage side and 3–5 discontinuous heating area appears in the middle part. It was named “Lantern-like” heating failure according to the shape of the heating area. With the withstand voltage test, absorption test, X ray micro-CT test and SEM analysis, The 3D structural imaging of the through channels in the rod has been achieved, which would change the electric field distribution significantly. Short internal through channels will change the electrical field distribution and provide the energy to the abnormally heating. To detect these potential channels which should be responsible for the abnormally heating in the rod, the test time of dye penetration test has been extended from 15 minutes to 2 hours, and the improved test methods can find the through channels easily but won’t alert for the normal ones.