Dissolved gas analysis is the most common and well-established method used in identifying internal faults of power transformers. However, an onsite analysis using this method accuracy still need to be improved while the laboratories analysis process takes longer time. New alternative onsite and online method are most urgently need to be studied. Power transformer faults identification based on extended application of polarization and depolarization current (PDC) measurement data on oil sample from in-service power transformer was investigated in this research. The changes in the molecular properties of the insulating oil due to different fault conditions found had influenced the initial time response of the PDC measurement (from 0 to 100 s). In this research, the unique characteristic pattern of each condition was determined by a single unique numerical dimensionless quantity known as depolarization ratio index (DRI). DRI is used to express the changes of depolarization current shape with different fault conditions. The ratio of depolarization current between 5/100 and 10/100 s was found to have a better correlation at least more than 90% on the incipient fault in power transformer. Indeed, the DRI at 5/100 also was observed has higher accuracy especially on units with normal, overheating and arcing condition. In addition, a graphical representation of DRI value at 5/100 and 10/100 s was proposed for fault recognition in power transformer. Both DRI and graphical representation are well validated, and the proposed interpretation techniques have accuracy of more than 90% and able to identify and classify the normal, overheating and arcing condition of the in-service power transformer.

溶解气体分析是用于确定电力变压器内部故障的最常见且完善的方法。但是，尽管实验室分析过程需要更长的时间，但仍需要使用这种方法进行现场分析，以提高准确性。迫切需要研究新的现场和在线替代方法。研究了基于极化和去极化电流（PDC）测量数据在役变压器油样的扩展应用的电力变压器故障识别方法。由于发现了不同的故障条件，绝缘油的分子性质发生了变化，从而影响了PDC测量的初始时间响应（从0到100 s）。在这项研究中 每个条件的独特特征模式是由一个称为消极化率指数（DRI）的唯一独特的无量纲数值确定的。DRI用于表示不同故障条件下的去极化电流形状的变化。发现在5/100和10/100 s之间的去极化电流比与电力变压器的初期故障之间的相关性至少好于90％以上。实际上，还观察到DRI为5/100时具有更高的精度，特别是在正常，过热和电弧放电条件下的设备上。另外，提出了在5/100和10/100 s时DRI值的图形表示，用于电力变压器的故障识别。DRI和图形表示均已得到充分验证，