Thermal aging results between oil-paper insulation impregnated by mineral and vegetable insulating oil

This paper presents accelerated thermal aging experiments of oil-paper insulation involving insulating paper, mineral insulating oil, vegetable insulating oil and the mixed insulating oil, which is combined by vegetable and mineral insulating oil with different proportions. The proportion of vegetable and mineral insulating oil (PVM), defined as a mass ratio of the vegetable insulating oil to the mineral insulating oil in mixed insulating oil. The experiments were implemented at 130 °C to analyze the aging products characteristics of different types of oil-paper insulation samples. Experimental results showed that acid value and furfural content of insulating oil also increased with aging time, which were both related to the PVM of mixed oil. The degree of polymerization (DP) of insulation paper decreased with aging time. The declining rate of DP decreased with increasing PVM of mixed oil. Analysis results indicated that vegetable insulating oil restrained the degradation of oil-paper insulation during the thermal aging process. Vegetable insulating oil shows good performance in electrical, high anti-aging ability and environmental protection. Thus vegetable insulating oil is considered as a promising substitute for mineral insulating oil in power transformer. It has the potential to refilled mineral insulating oil by vegetable insulating oil.