Gassing behavior of various alternative insulating liquids under thermal and electrical stress

Dissolved gas in oil analysis (DGA) has been used for many years successfully for diagnosis and condition monitoring of mineral oil filled transformers. Due to the usage of alternative dielectric liquids, for example natural and synthetic esters, it is necessary to investigate if and how this diagnostic method can be applied to these insulating systems. This contribution presents the gassing behavior of different insulating liquids from experiments, which represent electrical and thermal faults. Also the suitability of existing mineral oil interpretation methods for DGA is considered. One mainly investigated fluid is Envirotemp FR3 (TM). Where possible the amount and relation of gases are compared to mineral oil and other synthetic esters' gassing behavior.