Dissolved Gas Analysis Results in Wind Turbine Transformers

In recent years there have been issues of unusual dissolved gas analysis (DGA) results from routine testing of wind-turbine transformers. These are differences when compared to results from tests of standard oil-filled distribution transformers. This paper reports on a comparison of DGA test results for such transformers in Australian wind farms. The results were analysed for their predictive potential fault effects using data from a number of locations around Australia. They were analysed using the Duval Triangle representation which allows multiple DGA results to be easily compared. Results from wind and grid transformers were compared from Australian laboratories. The results show significant differences which indicate different apparent sources of dissolved gases for the two transformer groups. Wind turbine transformer results were predominantly of electrical discharge origin while grid transformer results were primarily thermal in origin. While the data used for the comparison was limited the differences are quite distinct and support similar differences found in North America. This paper looks at possible sources of discharge activity and their connection to characteristics of wind turbines.