Research on Excitation Surge Characteristics of 220 kV Transformer

During the process of transformer no-load closing or external fault removal and voltage recovery, excitation inrush currents with amplitudes up to several times or even ten times the rated current will be generated. This surge only passes through the power supply side of the transformer and will inevitably flow into the transformer differential current circuit, which may cause the longitudinal differential protection to malfunction. This article establishes a simulation model in Matlab/Simulink based on the actual parameters of the 220 kV transformer, and simulates the excitation inrush current of each phase of the transformer under different initial closing phase angle conditions. On this basis, the mechanism of excitation inrush current generation, interruption angle, and second harmonic were studied and analyzed, also engineering suggestions were proposed.