Rationale for Use of Grade I - III Distribution Transformer Efficiency Calculation Technique Taking into Account Correlations Between their Parameters and Amount and Type of Power Supply Load

A distribution transformer shall be selected by the anticipated load schedule and the correlations between transformer parameters and operating conditions. This research aims to justify the use of the developed energy-efficiency assessment technique for the transmission of electric power by Grade I-III power transformers used in power distribution grids. It featured a DCP and accounted for the correlations between transformer parameters and the load amount and type. To assess the absolute error of the developed technique, we used the computer models of power supply systems with transformers of respective grades developed in the Multisim software. The comparison of the developed efficiency calculation expression for power transformers with DCP and the conventional Grade I-III power transformer expression showed that the developed expression has a greater accuracy for the entire range of the rated power parameters of distribution transformers, and the greatest accuracy improvement effect was observed for Grade 1 transformers. Using the developed expression to calculate the efficiency of Grade I triple-phase double-winding power transformers with DCP can improve the calculation accuracy by 3.7 times compared to the median values. Simultaneously, the variation range is reduced by 5.3 times, the decimal and interquartile range by 4.5 times, and the root-mean-square deviation by 4.8 times. The developed efficiency calculation technique for triple-phase double-winding transformers can reduce the amount of absolute error in the calculated energy efficiency compared to the conventional formula which has some drawbacks associated with the assumptions made during its development.