Development of MV class transformer with hybrid insulation

Pole transformers of MV class have utilized an insulation system consisting of natural cellulose-based materials and mineral oil for many years. If transformers are subjected to rapidly changing overload conditions, insulation materials can see high temperatures leading to unexpected aging. Therefore, we have been conscious of developing a transformer that is more thermally stable than conventional types. To measure temperature distribution in the winding of conventional and newly designed transformers, temperature sensors were installed for direct reading of the transformer oil and conductor temperatures of transformers. We also conducted accelerated aging tests for these transformers. The measurement data was utilized in the design of the hybrid insulation system. Also, we found the possibility of applying this insulation system in 13.2 kV pole mounted transformers.