Weibull statistical analysis of area and volume effects on the breakdown strength in liquid nitrogen

In order to examine the area and the volume effects on breakdown strength in liquid nitrogen (LN₂), we measured dc and ac breakdown voltages in LN₂ with sphere to plane and coaxial cylindrical electrode configurations. We also carried out statistical analysis of the experimental results using the Weibull distribution and discussed with the statistical stressed electrode area (SSEA) and/or liquid volume (SSLV). The dc and ac breakdown strength in LN₂ decreased to 1/5 with increasing SSEA and SSLV over the wide range from 10⁰to 10⁵ mm² and from 10^-1 to 10⁵ mm³, respectively. The Weibull shape parameter m for the sphere to plane and the coaxial cylindrical electrodes was estimated to be 6 to 8 and 11 to 13, respectively; the breakdown strength in LN₂ saturated with increasing SSEA and SSLV. From these results, it was verified that the area and the volume effects definitely determined the breakdown strength in LN₂. The results of the Weibull statistics were compared with the conventional concept of the stressed electrode area (SEA) and liquid volume (SLV). Consequently, SSEA or SSLV was found to be nearly equal to 80 to 85% of SEA or SLV