Evaluation of the efficiency of replacing one power transformer with two in 10/0.4 kV single transformer substations under seasonal load

The efficiency of replacing one power transformer with two in 10/0.4 kV single transformer substations under seasonal load has been evaluated using the example of replacing a 100 kVA transformer. The installation of two transformers with capacities of 40 and 40 kVA; 40 and 63 kVA; 63 and 63 kVA has been considered. The effects of reducing electricity losses have been evaluated depending on the load factors of transformers and on increasing the reliability of power supply to consumers. The variants of circuits of a single-transformer non-automated, automated substation and an automated substation with two transformers have been compared. A methodology for evaluating the effectiveness of options has been developed. The most rational option in the considered example is to replace it with two 63 and 63 kVA transformers. It achieves the effect of reducing electricity losses with an average annual load factor of 100 kVA equal to or less than 0.35, as well as with a load factor of 100 kVA equal to or greater than 0.55. The effect of increased reliability is to reduce the time of interruptions in the power supply to consumers from 9.44 hours/year to 0.79–1.33 hours/year, depending on the amount of electricity consumed from the transformer substations.