Failure statistics and power transformer condition evaluation by dissolved gas analysis technique

Due to the degradation of power transformer under its normal and abnormal operating conditions, maintenance activities are vital to restore the condition. However, the preventive maintenance costs are now of primary concern. The scattering failure data are systematically recorded and analyzed to determine the critical component of power transformer. Two transformer models of rated voltage 115/22 kV and 230/115/22 kV have been chosen in this study. The determined critical component with high failure rate requires careful attention. The preventive measures can be setup from the known causes of failure. Then the procedure for power transformer condition evaluation is performed by analyzing the historical test result from the dissolved gas analysis (DGA) method. The transformer conditions are principally evaluated by the key gas method and then verified by the ratios and total combustible gas method. As a result, the aging pattern and trend of the power transformer deterioration can be determined.