Dissolve Gas Analysis Due to Partial Discharge Fault in Transformer Oil

Abstract

Power transformer is the most vital electrical equipment in power system. Protection of transformer keeps much more attention in order to fault free electric supply, efficiency and to exploit lifespan of the transformer. Thermal or electrical fault in transformer oil decomposes the organic compound of oil. Decomposition of oil generates gases which dissolve in transformer oil. The gas in oil has information about types of fault. The gas identification being produced has very beneficial information in any blocking maintenance program. For detecting these there are many technique gases and dissolve gas analysis (DGA) is accepted as a most useful technique. This technique includes sampling of oil & testing of sample to measure the dissolved gases concentration in ppm level. The dissolved gases are: CH4, C2H2, C2H4, H2, C2H6, CO2, CO, N2, O2, and H2O. These are key gases which are useful for finding incipient fault in the transformer. There are several interpretation techniques based on DGA such as Dornenburg method, IEC Standard Code, Key-Gas method, Rogers’ ratio and Duval triangle method. The diagnostic accuracy of these techniques is very limited. The combination of these method is useful in improving the accuracy of fault diagnosis.