Off/on-line FRA condition monitoring technique for power transformer

This letter presents a novel and sensitive frequency response analysis (FRA) technique for off/on-line condition monitoring of expensive power apparatus. The main objective is to investigate the applicability of this predictive maintenance technique to diagnosing power transformer failures, to characterize the transformer in a frequency plane for safe operation, and to develop on-line monitoring technique. The effectiveness of this technique is demonstrated on a 2.5 MVA transformer housed at the High Voltage Laboratory of Pacific Power International (PPI) and then tested on three field transformers. The on-line technique is verified on a single-phase high voltage transformer. This study shows that FRA results are very sensitive to faults. The configuration of the measurement set up, frequency range and terminations play a greater role in getting reproducible, fault-indicating results. The interpretation of the voluminous data and analysis relevant to the faults opens a gateway to develop smart power apparatus.