Onsite Partial Discharge Testing on Power Transformers - Case Study

A failure of a Power Transformer during his operation on the grid could lead to huge impact on the network due to accidental power outage, and to unnecessary loss of energy and money. To prevent this kind of incident, periodic check and tests must be done on Power Transformers in order to obtain a clear picture on their health conditions, and therefore to take the right corrective measures at the right time. Besides the conventional Testing methods, advanced testing tools, such as Partial Discharges tests, has been developed during the last years, which has added high values and positive impact on the diagnostic methods Technics of Power Transformers. This paper describe the main aspects of Partial discharge testing on Power transformers, why and how the test is performed and show, through a case study, the different steps of this measurement and the different analyzing tools commonly used to identify the PD source in Oil filled Power Transformers.