Morphologic analysis and diagnosis of defects inside cast resin medium voltage current transformers insulation by digital partial discharges acquisitions

This work presents a systematic experimental campaign about the recognition, the morphological analysis and the diagnosis of defects inside the mass insulation of medium voltage current transformers. Different kinds of common defects (voids, delaminations, etc.) have been intentionally produced inside the mass insulation and on the surface of the test objects. External influence parameters, such as surface pollution, have been taken. All the sample test pieces are subjected to several PD tests and the relevant acquired data are stored and processed. The outcome evidences that digital PD acquisitions may allow to efficiently spot the defects and to identify their morphology.