Research progress on insulation condition estimation for oil-immersed power transformer

Chinese power industry developed rapidly recent years, and the problem of safety and reliability of power equipment is increasingly outstanding. The development of new test technology and the introduction of artificial intelligence (AI) are driving the monitoring and diagnosing method on insulation condition forward, and nowadays gradually changing the maintenance strategy from breakdown maintenance (BM) style to time based test and maintenance (TBM), then to condition based maintenance (CBM). This paper reviews the progress in estimation on insulation condition of oil-immersed power transformer, and summarizes the currently used test and monitoring methods. Some new methods employing dielectric response phenomena are being studied and promising for on-site test. And an intelligent transformer concept is also promising in the near future. And some unsolved problems in the field of condition monitoring and diagnosis (CMD) are proposed.