Test Method for Crack Selection in 10kV Pin Insulators

Kim Ryul, a researcher at the Faculty of Electrical Engineering, has realized selection of crack insulators from a pile of 10kV pin insulators by data processing of thermal shock sample breaking test and a corona short-circuit nondestructive test device.

Compared with previous selection methods by electric penetration breakdown test, this method provides more safety and lower production cost. In addition, as it uses nondestructive electric tests to sort out crack insulators, the reliability of production pile of insulators can be further improved.

This method is constructed with several stages: determination of size of 10kV pin insulator piles and samples, thermal shock sample destructive test, state decision of pass or pass failure of production piles by processing test data, determination of acceptance probability by quality control software and of the number of faulty insulators, and selection of crack pin insulators by the corona short-circuit nondestructive selection device.

This thermal shock test costs less and provides 1.4 times higher accuracy than the previous electric penetration breakdown test. To estimate cracks in 10kV pin insulator piles, previous binomial distribution was replaced with noncentral t-distribution, which reduced the number of samples to half and improved the accuracy of acceptance probability of piles and the calculation of the number of crack insulators by 1.2 times. Instead of electric penetration breakdown test devices, corona nondestructive test devices were used, which made it possible to select 100% of crack insulators from passed piles.