Interpretation of DGA data and its use in the detection of malfunctions [transformers]

Dissolved gas analysis (DGA) has been used for more than 20 years to evaluate the behaviour of oil filled electrical equipment. The analysis carried out by gas chromatography, allows the determinations of the principal gas, hydrogen, hydrocarbons in C1, C2 and C3 and carbon oxides, which can be generated by an oil impregnated insulation under various fault conditions. The IEC 567 Publication gives the sampling and analysis methods. Its revision, which has now been completed by IET TC 10, includes the test methods with the latest improvements and specifies the detection limits following the analysis concerning samples taken in apparatus in service or samples taken during factory tests. The author discusses the interpretation of the DGA including diagnosis of the condition of equipment and the nature of the fault at the origin of gas production