An accelerated ageing test bench for lifetime assessment of new generation of MV/LV transformers

Effective asset management of electric network components is crucial for the DSO (Distribution System Operator) to ensure high quality and reliable energy distribution. Transformers have undergone significant design evolution in recent years, due to the development of new dielectric fluids and Ecodesign regulation. In this context, transformers are among the most critical equipment. Therefore, a thorough understanding of the degradation processes within operating transformers is essential to assess their residual lifespan and plan their replacement. This paper presents a new experimental test bench allowing to simulate the ageing behaviour of real transformers cellulosic insulation. Thermal ageing of two distribution transformers, one filled with mineral oil and the other with synthetic ester, both using thermal upgraded paper (TUP) are evaluated and compared using the experimental test bench. The mineral oil-immersed transformer serves as a reference while ester-immersed transformer is used to study the behaviour of the transformer using synthetic ester oil combined with thermally upgraded paper. The ageing progress is evaluated according to the loading guide IEC 60076-7 standard. The results of this study still ongoing, once finalized, could be the subject of a subsequent publication.