Diagnostic techniques to evaluate internal condition of power transformer

The diagnostic techniques to evaluate the internal condition of power transformer are presented in this paper. The techniques consist of electrical testing and insulating oil testing with their associated limitation to classify normal and abnormal conditions. The electrical diagnostics include exciting current, leakage impedance, ratio, DC resistance as well as core and winding insulation measurements. However, only the leakage impedance measurement is selected to present in this work as an example. In the insulating oil test, the DGAF and the amount of key gases are proposed to analyze the possible causes of failures. This method with further development could be used to effectively determine the condition of transformer components.