More accurate breakdown voltage estimation for the new step-up test method

The step-up method is used to estimate the impulse breakdown voltages when the electrical insulation is not usable after it is broken. This paper analyses the reliability of the estimates of the underlying breakdown probability distribution in the step-up method, when (1) the observed breakdown voltage itself is available and (2) it is not available. The former case has many advantages compared to the latter case such that (i) the confidence intervals of the estimates become smaller and (ii) the estimates can be obtained with higher probability. Consequently, this paper recommends using the estimates of the underlying distribution for the breakdown voltages instead of the nominal breakdown voltages. Some illustrative examples are given.