Abstract
A high voltage, large capacity power transformer is one of the most important equipment in electric power system. If a failure occurs in such a transformer, stable power supply may become impossible. In addition, efficient power system operation may become difficult because it takes long time to replace the transformer. To prevent failures that may occur, effective external diagnosis must be performed and the defective portions must be correctly identified. However, such anomalous phenomena are complicated in many cases, and their causes cannot be identified in some cases by using conventional techniques.
This paper reports a case study on the fault diagnosis of an oil-immersed power transformer that had a tendency to increase in the total combustible gas (TCG) during a regular operation. Specifying the faulty parts became possible by applying various case of Frequency Response Analysis (FRA) diagnosis though it was impossible by the electrical tests, DGA (Dissolved Gas Analysis), and so on. This transformer was disassembled to investigate the condition and was replaced without causing failure.
