| Abstract: | We measured dc and ac breakdown voltages in liquid nitrogen (LN 2) with a sphere-to-plane electrode configuration. Experimental results revealed that the breakdown voltage in LN2 did not increase monotonously but partially decreased as the sphere diameter increased at a constant gap length. Thus, the existence of the area and the volume effects on the breakdown voltage in LN2 was verified quantitatively; the breakdown strength decreased when increasing the {SEA}90 (90% stressed electrode area) and the {SLV}90 (90% stressed liquid volume). By changing the experimental conditions, it was verified that both area and volume effects, having a mutual correlation, simultaneously lead to the degradation of the breakdown strength in LN2. In order to examine the area and the volume effects for the larger {SEA}90 and {SLV}90, we also measured the breakdown voltage with a coaxial cylindrical electrode. It was concluded that the dc and ac breakdown strengths in LN2 decreased as the {SEA}90 and the {SLV}90 increased varying widely from 100 to 105 mm2 and from 10 -1 to 105 mm3, respectively |
