Electrode Area Effect for the Impulse Breakdown of Transformer Oil

In a previous paper (1), the necessary experimental and theoretical basis was established for a discussion of the effect of electrode area on the 60-cycle breakdown of transformer oil. A study of 1600 observations established the extremal nature (2) of such breakdown distributions and yielded an equation relating area and voltage which agreed closely with test results. This equation is: V A1 − V A2 = s v /σ N 1n A 1 /A 2 (1) where V is the modal strength and s v is the standard deviation of N measured breakdown values; σ N is a function of the number of breakdowns N only.