The new S9 series three-phase oil immersed transformer complies with the national standards GB1094 "Power Transformers" and GB/T6451 "Technical Parameters and Requirements for Three phase Oil immersed Power Transformers". It adopts multiple scientific research achievements such as new insulation structure and improved short-circuit resistance structure, and uses new processes, high-quality materials, advanced equipment and other means. Its performance has reached the international advanced level. Compared with the S7 series, the average no-load loss has been reduced by 37.g%, and the average load loss has been reduced by 22.4%. It is a key energy-saving product promoted by the country.