AC Breakdown Characteristics of Different Moisture Content Pressboards Impregnated with Natural Ester

Abstract

Abstract-Biodegradable materials are necessary for saving the environment. Natural ester is alternative liquid insulation that can be biodegraded and used in a transformer. Insulation system in a transformer, liquid insulation cooperates with solid insulation such as cellulose. Pressboard is the main kind of cellulose used in the transformers. Normally, the characteristics of solid insulation can be investigated and analyzed by diverse methods. This paper represents the study of AC breakdown voltage of non-impregnation, 8-hours, and 16-hours impregnated pressboard with natural ester with different moisture content. To vary the moisture content of the pressboards, they were heated at 100 degrees Celsius for 12 hours and 24 -hours in a vacuum oven. After that, the Coulometric Karl Fischer method was used to determine the moisture content. Before impregnation, the natural ester was heated at 100 degrees Celsius for 12-hours in another vacuum oven. To investigate AC breakdown voltage, electrode configuration and test circuit were set-ups according to IEC 60243-1. From the test result, higher’ moisture content caused clearly lower AC breakdown voltage of the pressboards.