Effect of Insulation Thickness on Deterioration Characteristics of Oil-Paper Insulation under Switching Impulse Voltage

Oil immersed inverted current transformer is vulnerable to overvoltage in the transmission line during operation. The accumulative effect of switching impulse voltage can degrade the main insulation and lead to a reduction in insulating property. In order to investigate the deterioration characteristic of main insulation of oil immersed inverted current transformer under the accumulative effect of switching impulse voltage and indicate the insulation deterioration, we studied the E-N characteristic of oil-paper insulation with different thickness and gave corresponding semi-empirical formulation to characterize the deterioration characteristic of main insulation of oil immersed inverted current transformer. The influence of insulation thickness on insulation deterioration of oil paper was studied as well. The results show that, the oil-paper insulation has a significant accumulative effect under switching impulse voltage. The E-N characteristic of oil-paper insulation conforms to power exponential distribution. With the increase of insulation thickness, the single minimum breakdown electric field strength decreases gradually.