On the influence of the connection scheme of windings of power transformers with a higher voltage of 6-10 kV on the operational parameters of rural electric networks

THE PURPOSE OF THE STUDY. The work is aimed at identifying the influence of circuits and groups of connection of windings of power transformers on the operational parameters of rural electrical networks of 0.4 kV. RESEARCH METHODS. The influence was estimated by the magnitude of short-circuit currents determined in accordance with GOST 28249-93, power losses in the windings of power transformers and the magnitude of currents flowing on the 10 kV side of the power transformer during 0.4 kV network short circuits calculated by the method of symmetrical components taking into account the transformation of currents. THE RESULTS OF THE STUDY. In the course of the study, it was revealed that when using transformers with a Y/Zn winding connection scheme, the single-phase short-circuit currents in the network are the greatest. At the same time, transformers with a Y/Yn winding connection scheme are characterized by lower power losses. When using transformers with a D/Yn connection circuit, the currents in the 0.4 kV mains on the 10 kV side are greater than when using other circuits. CONCLUSIONS. The choice of transformers with the Y/Yn scheme is rational for small line lengths of 0.4 kV, Y/Zn for large line lengths and asymmetric load, D/Yn for large line lengths and relatively symmetrical load.