Power Transformer Oil-paper Insulation Breakdown Tests in Full Scale Models

In order to eliminate the influence of volume effect and evaluate dispersibility, a full scale winding insulation test platform with the same structure as 500kV power transformer windings is constructed. Winding insulation in normal condition, high gas content in oil condition, high moisture level in oil condition and aged winding insulation condition are modeled. AC breakdown tests are conducted with winding models in two types of inter-turn insulation thickness, 1.35mm and 1.95mm, in these insulation conditions. Testing results are hence summarized and analyzed. Another oil-gap insulation test platform with a 500kV transformer bushing installed is constructed. AC breakdown tests with the oil gap between the bushing end shield and the tank wall earthing electrode in 15mm are conducted. Testing results with oil in normal condition, high resolved water content condition and high suspended water content condition are compared and analyzed. Finally, comparative tests are conducted with bushing end shield insulated with paper coating.