Failure Statistics and Condition Evaluation for Power Transformer Maintenance

Power transformer has degraded under its normal and abnormal operating conditions, maintenance activities are vital to restore the condition back to the normal condition. Even though the traditional preventive maintenance is well known and successfully performed, but the method had a high cost. Therefore, the objective of this paper is to improve the drawback by systematical record of the scattering failure statistics and analysis, in order to determine critical component. Power transformer models of rated voltage 115/22 kV and 230/115 kV have been adopted based on the available technical data, history test record and number in service. The component with high failure rate must be carefully focused. The known causes of failure could be prevented. Furthermore, the component with the highest percentage of failure is analyzed by Weibull distribution in order to estimate life time which can be used to support in maintenance activity. The procedure for power transformer condition evaluation is performed by analyzing the historical testing result from the Dissolved Gas Analysis (DGA) method. The transformer conditions are principally evaluated by the Key Gas method and then verified with the other methods. As a result, the aging pattern and trend of the power transformer deterioration can be determined.