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.

This paper addresses frequency response feature extraction of analog filter circuits. An approach for feature selection using criteria of maximum relevance minimum redundancy (MRMR) and support vector machine (SVM) isproposed. Key idea of the method is to obtain candidate feature subsets with descending order using criteria of MRMR first, and then to select the optimal feature subset through cross validation results of each feature subset using SVM. Experimental results testity that the proposed approach has the advantages of less time-consuming and the selected features have reasonable distribution.

No abstract

No abstract

No abstract