Using diagnosis gas analysis as a tool for power transformer maintenance

Abstract

The importance of Diagnosis Gas Analysis (DGA) has been recognized by electrical industry nowadays as one of the tools for power transformer maintenance to monitor the performance of transformers and provide early information about the health of a transformer. The lifespan of a transformer depends on the condition of the transformer oil. Transformer problem causes an increase in temperature of transformer components, thereby increasing the temperature of the insulating. When the oil is exposed to heat, it will result in the formation of a number of gases dissolved in transformer oil. The purpose of this research is to investigate the relationship between dissolved gases in transformer oil and its relationship to the damages suffered by the transformer. This research used oil samples taken from a number of power transformers installed in Tenaga Nasional Berhad, an electrical utility company in Malaysia. Oil samples were sent to a laboratory for analysis. This research is aimed at finding the causes and consequently identify damages to the components by using five methods of interpretation using the DGA namely Rogers Ratio Method, Doernenburg Ratio Method, IEC Method Ratio, CIGRE Ratio Method and Duval Triangle Method Ratio Method. Three actual cases are discussed in this thesis based on the investigation and repair works on 132kV and 275kV transformers. It is found that DGA can be used to locate defects in the components of the transformer.