A review of monitoring methods for predictive maintenance of electric power transformers based on dissolved gas analysis

Electric power transformers are the link between the generators of a power system and the transmission lines and between lines of different voltage levels. Power transformers undergo changes in their operational life expectancy and reliability over the years. Currently, several tools for diagnosis and assessment of their operational condition are available, including diagnostic techniques based on dissolved gas analysis in the insulating oil. Through monitoring of dissolved gases in oil, it is possible to perform detailed data analysis, seeking systemic failure prediction. The adoption of new technologies for maintenance of power transformers can induce substantial changes in the reliability of such equipment in view of the existence of a global trend to decrease operational costs, predict maintenances and control substations in a centralized way. This paper describes the main factors that lead to lifetime reduction in transformers and reviews the main methods used for predictive maintenance based on dissolved gas analysis. The advantages and disadvantages of each one are outlined and some future directions for research are proposed.