Comparative study and analysis of DGA methods for mineral oil using fuzzy logic

Abstract

Dissolved gas analysis (DGA) is one of the most useful techniques to detect the incipient faults in large oil-filled transformers. Various methods have been developed to interpret DGA results. Among them are the Key Gas, Rogers Ratio, Logarithmic Nomograph, Doernenburg, IEC Ratio and Duval Triangle. This paper used the DGA data from 69 different cases to test the accuracy and consistency of these methods in interpreting the transformer condition. The key gases considered for evaluation are hydrogen, methane, ethane, ethylene and acetylene. MATLAB programs with and without using fuzzy logic were developed to automate the evaluation of each method. The difference on accuracy and consistency of each method using and not using fuzzy logic is presented.