Deterioration Characteristics of Model of Insulating Spacer for GIS under AC and Impulse Voltage

With decrease of the ratio of lightning impulse withstand voltage (LIWV) to rated power frequency voltage (AC) of power system, concerns are directed to the long term deterioration of the insulating spacer composing GIS by higher power frequency stress. An aging test of epoxy insulating spacer is carried out under rated power frequency voltage and 2, 300 Hz voltage which is evaluated to have the equivalency of frequency acceleration to investigate the long term deterioration characteristics of the insulating spacer. The test samples of the insulating spacer are divided into several groups and the samples of the same group are stressed at the same electric stress up to 22 kVrms, /mm. As the result, it is found that the reduction of lightning impulse breakdown voltage after aging is more considerable than the reduction of AC breakdown voltage. From these results, it is estimated that power frequency stress level which deteriorate scarcely the insulating spacer is about 12 kVrms/mm.