Case studies of transformers investigations with DGA and winding resistances

Power transformers, designed to transmit electrical power, are key components for the electrical grid and industrial processes. The transformers breakdowns generally lead to important availability losses principally due to difficulty to repair or exchange. Unavailability has a high cost in term of productivity and service quality. Unfortunately, due to their technical specificities and their high costs, the trend is to keep them in service as long as possible with lowest maintenance cost possible. To achieve such objectives, transformer health management techniques become more and more important. The transformer diagnosis tools are traditionally based on measurement analysis and expert knowledge.