Discharge characteristics of air gaps stressed by AC, DC and impulse voltages obtained at proficiency tests in Japan

The Japanese Accreditation Board (JAB) has carried out proficiency tests accorded with ISO/IEC Guide 43-1:1997 to confirm the skill of high voltage testing laboratories in Japan every year since 2002. Contents of these tests are to measure gap length vs. discharge voltage characteristic of "rod-rod" and "rod-plane" gaps stressed by AC, DC, lightning impulse or switching impulse voltages. An average of seven laboratories participated in the proficiency test every year; each z-score is compared and the confirmed ability is promulgated. Each combination of the voltage type and the gap type was selected every four to six years. These tests were carried out at gap lengths from 10 to 100 cm, and the humidity range was from 2 g/m3 to 13 g/m3. The huge data obtained through those proficiency tests…