Method for Calculating Efficiency of Distribution Transformers Using Semi-Constant Coefficients and Taking Into Account Interdependence of its Parameters and Magnitude and Nature of Load of Power Supply Facility

Power transformers operated in electrical distribution grids shall be optimally integrated into the grid with the existing load for the minimum cost of energy transformation. At any given time, the transformer load is defined by the power consumption schedule. Thus, the selection of a distribution trans-former should not consist in choosing ID and SC losses from the catalogs of manufacturing plants, but in choosing them on the basis of the anticipated schedule of transformer loading and taking into account the interdependence between transformer pa-rameters and operating conditions. Conducting the research re-lated to the development of a new methodology for evaluating the energy efficiency of electric power transmission by power trans-formers operated in distribution electric networks. To implement the proposed methodology for calculating the efficiency of power three-phase double-winding transformers, a replacement circuit of the “double-winding transformer - load” module was used, and aT-shaped equivalent circuit was used for the power trans-former, characterized by the use of semi-constant coefficients and taking into account the interdependence of transformer parame-ters and the load magnitude and nature. The developed method for calculating the efficiency of distribution transformers takes into account the characteristics of the load of the power supply facility, since the expression for calculating efficiency is presented as a function of two variables: active and inductive load re-sistances modified to the HV winding, which facilitates the selection of a limited set of power transformers, a power transformer providing economic quasi-optimality, contributing to maximum economic energy efficiency of power supply.