Effect of DC Electric-Thermal Aging on Space Charge Behavior in Oil Paper Insulation with Air Gap/Oil Gap

Abstract

In order to understand the change characteristics of space charge in the oil paper insulation under the condition of air gap defect and oil gap defect, first, the insulating oil and insulating paper are subjected to the electrothermal combined aging, and the space charge measurement experimental platform is built. During the process of applying direct current voltage, the relationship between the electrothermal combined aging degree of oil paper insulation and the evolution of its space charge characteristics under two kinds of defects is analyzed. The experimental results show that the peak value of the interfacial charge of the oil paper insulation sample increases at first and then decreases with the increase of time in the process of applying DC voltage. However, electrothermal combined aging can reduce the maximum peak value of the charge at the interface of the oil paper insulation sample and shorten the time of the interface charge reaching saturation. The existence of air gap will hinder the migration of negative polarity charge to the upper insulating paper, while the oil gap enhances the migration of negative polarity charge. Therefore, with the increase of the electrothermal combined aging degree, the charge peak at the interface between the upper insulating paper and the gap presents different changing trends. In the air gap model, the charge change at the interface decreases after reaching saturation, while in the oil gap model, the charge change at the interface maintains after reaching saturation.