Dissolved Gas Analysis (DGA) of Arc Discharge Fault in Transformer Insulation Oils (Ester and Mineral Oils)

Transformer insulation oil is an important liquid for insulating and cooling of transformers. For many years' mineral oil has been used for as an insulating liquid in high voltage transformer. Mineral oil has good dielectric properties, however, due to environmental problem; recently many researchers have been looking for an alternative insulating liquid. Biodegradable and environmentally friendly ester oils have attracted more attention in recent years. This paper presents the experimental results of electrical arc stress on dissolved gases of transformer insulating oils (PFAE, MIDEL 7131 and mineral oil). The generated dissolved gases in the sample oils were examined by dissolved gas analysis (DGA) techniques. The test device used for testing is acrylic tube with a high voltage copper electrode at the top and a ground aluminum electrode at the bottom immersed in the oil. The experimental results from dissolved gas analysis (DGA) indicated that arc fault produce large amounts of hydrogen (H₂) and acetylene (C2H2) with small quantities of methane (CH4), ethylene (C2H4) and ethane (C2H6) for both oils. Acetylene (C2H2) gas is the highest combustible gas generated by arc discharge in both mineral and ester oils. Therefore, there is a possibility that the diagnosis of a transformer filled with ester oil can be done using dissolved gas analysis (DGA) method.