Application of Weibull insulation reliability evaluation method to existing experimental data with one-minute step-up test

The reliability evaluation using a Weibull distribution function is studied at the point of handling the coexistence of multiple voltage levels. In this paper, an insulation test based on the one-minute step-up method is used in order to calculate and evaluate the appropriate test results using the "independence model" or "accumulation model". First, the existing measurement data were reviewed, which included data on insulating elements of oil-filled transformers and data on penetration breakdowns of epoxy spacers of gas insulated switchgear. These sets of digital data were subjected to digital processing on a consistent basis, and various parameters were calculated using the same method to summarize their insulating properties. Next, the results of the one-minute step-up test were calculated under the "independence model" and the "accumulation model" to examine which of the models the insulating properties of targets conform to. It was found that, in the one-minute step-up test, the measurement results, particularly the 50% breakdown voltage values, were between the calculated values under the two models in many cases and did not completely conform to either of the assumptions of these models. This is considered to be because part of the voltage application in a previous step partly leaves a cumulative influence.