The Influence of Oil-impregnated Insulation Paper's Thickness on Electrical Breakdown Strength

The oil-impregnated insulation paper (OIIP) is widely used in oil-impregnated high voltage apparatuses. The thickness is an important parameter which affects its electrical breakdown strength. This paper presents an experiment research on the influence of OIIP's thickness on breakdown strength under AC, DC and pulsating DC voltages. The short time breakdown experiments were executed and the Weibull distribution was used to process the results. The results show that the breakdown strength of OIIPs was significantly influenced by thickness and voltage waveform. The breakdown strengths of OIIPs with same thickness under DC and pulsating DC voltage are much larger than that under AC voltage. The breakdown strengths of OIIPs decrease with the increasing thickness under AC voltage, while the breakdown strengths increase with the increasing thickness under DC voltage. The breakdown strengths slightly increase with the increasing thickness of OIIPs under pulsating DC voltage (R=1) and pulsating DC voltage (R=1/3). The equivalent series model of OIIP was used to interpret the results, and the thickness of OIIPs influenced the electrical breakdown strength mainly through oil absorption rate.