The Doernenburg ratio method utilizes the ratios of the concentration of the key gases Hydrogen H2, Methane CH4, Ethane C2H6, Ethylene C2H4, and Acetylene C2H2. The following ratios are used CH4/H2, C2H2/CH4, C2H4/C2H6, and C2H2/C2H4.
For this method to be a viable diagnostic tool, a few criteria must be met. This is the negative aspect of this diagnosis method as there are more frequent than not “no diagnosis” obtained.
The criteria are such that for the transformer to be considered to have a problem at least one of the key gas concentrations must exceed twice a predetermined limit with at least one of the remaining three key gases exceeding its predetermined limit. There is also a further validity check that at least one of the key gases in each of the four ratios must exceed the predetermined limit for the ratios to be significant. Only then can the combination be compared to the codes. Once this criterion is met, the ratios are combined into a code, where each four-parameter code has a unique diagnosis that can identify thermal faults, corona discharge, and arcing [IEEE C57.104].
Use the following link to the “Analysis” section to get the Doernenburg diagnosis of the oil samples. Enter the oil sample under “Sample 5” to get the diagnosis.
Other dissolved gas analysis methods that may be of interest are: