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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. [ABSTRACT FROM AUTHOR]

Substation (SS) auxiliary systems (SAux) are facilities responsible for hosting the alternating (AC) and direct current (DC) busbar to serve the equipment and systems that perform the substation's protection, control, and supervision. External and internal power supplies typically ensure the continuity of such a facility. The electricity support will be restricted to diesel emergency generators (DG) if the external power supply is unavailable due to a contingency. The DG present a slower response time and are susceptible to starting failures. Microgrids with Battery Energy Storage Systems (BESS) paired with photovoltaic systems (PV) are presented as an innovative and reliable solution for powering the SAux. In this article, tests were carried out on the microgrid of the Edson Mororó Moura Institute of Technology (ITEMM) in Brazil to support the use of microgrids BESS/PV in the SAux of a transmission SS of the São Francisco Hydroelectric Company (Chesf). Without an external power supply, BESS commands the action of islanded operation, maintaining both voltage and frequency requirements of the microgrid without load shedding. It was possible to observe all operations of the microgrid. The experimental results showed that the solution proposed in the paper implements a dependable self-dispatchable autonomous power supply. [ABSTRACT FROM AUTHOR]

The analyses for overcoming problems arising in basic grid substation buses and equipment are of essential importance to the Brazilian electric sector in view of the constant expansion of this system. These analyses are not simple tasks because they involve an evaluation of the impacts caused by installations arising from new connections and because they always include various studies. This paper presents examples of necessary investigations into the causes of the rated characteristic violations of basic grid installation components. An overview of the proposed electrical system that will be evaluated in conjunction with a new thermal generator plant connection to an existing system substation system is presented. [ABSTRACT FROM AUTHOR]