when the insulation of a power transformer is subjected to excessive thermal or electrical stress, the links of the chemical compounds of the oil and the cellulose in the transformer can rupture and produce different gases. The analysis of the type and concentration of these compounds may represent the state of insulation of the transformer. There are three main approaches for this analysis: Analysis of gases through traditional methods, analysis of gases through the modeling of expert knowledge, and analysis of gases according to the historical evolution of the variables. This paper presents the design and development of a tool to monitor the transformers of different power stations, applying the three analysis approaches.