Chromatographic analysis of gases dissolved in the insulating oil reliably indicates thermal and electrical defects in the insulating system of oil appliance transformers (AT). AT manufactured in last decades are almost entirely hermetical (the decomposition gases do not get out). That is why a need of assessment of boundary concentrations that would be still permissible for safety operation of the machine arose. The published graphs show concentrations of some decomposition gases as they were measured out. In the graphs you can very well see the curve break, that was set as a critical point for deciding about continuing safety operation. The table shows mutual relations among the decomposition gases. Some discrepancies can be caused by hydrogen, which can most easily run out the sample.
