EFFECT OF HUMIDITY ON THE BREAKDOWN VOLTAGE OF INSULATORS AT VARYING HUMIDITY AND TEMPERATURE CONDITIONS

摘要

Breakdown voltage of insulators is strongly affected by atmospheric conditions such as temperature and humidity. Since the insulators are usually used at different atmospheric conditions from the test condition, it is essential to use a correction factor to obtain the real breakdown voltage from the test results. Some differences between the correction factors related to air gaps defined by IEC60060-1 and the ones resulted from current investigations, enhance the need of more studies to be done on breakdown voltage of insulators. We have tested 17 of 20 kV insulators comprised porcelain, glass, and composite with different arcing distances at varying atmospheric conditions. The corresponding humidity varied homogeneously from 1 gm/m~3 to 13 gm/m~3 in the 6*4*3.3 m testing room. Using the IEC humidity correction factors, the breakdown voltages measured in test conditions were turned into the voltages corresponding to standard conditions in order to make it possible to verify the accuracy of IEC humidity correction factor equations. Results obtained from comparison show that although the IEC gives good estimation for humidity correction factors, it needs modification in some cases.