Methodology for Cost Analysis of the Unavailability of Power Transformers in Brazilian Substations

Power transmission systems are made up of transmission lines and substations, and the main equipment in a substation are power transformers. Power transformers correspond to about 60% of the total cost of substations and are the most complex, being composed of several thermal, mechanical, electrical, and chemical elements and processes. Due to this complexity, unscheduled shutdowns occur in these transformers, which leads to the need for periodic maintenance and replacement. Within this context, this article proposes a methodology to analyze the costs generated by additional aging in transformers when subjected to an additional load caused by the shutdown of another transformer in the system. The methodology was validated in a case study carried out in a company in southern Brazil. The results show that the cost of unavailability is considerably higher when scheduled outages occur. It should also be noted that the 5 transformers studied are responsible for 93% of the unavailability cost, and the common fact among these is that the average normal load is above 50%. In this sense, it can be concluded that the methodology can assist in decision-making related to the management and maintenance of this critical equipment causing significant economic consequences in the long run.