Identification of Power Transformer Leakage Inductance When Energization

Abstract

The algorithm to calculate transformer leakage inductance, which is based on the loop equation of transformer, needs to have the values of voltages and currents at both sides of transformer. However, in existing substations, the voltage at no-load side of transformer cannot be obtained during its no-load closing, so a new method to calculate transformer leakage inductance that is suitable to the condition of no-load closing of transformer is proposed: so long as knowing the resistance and leakage inductance of transformer under normal condition and utilizing recurrence method in difference equation, transformer leakage inductance under its no-load closing can be rapidly calculated. On this basis, the leakage inductance is normalized to make the setting of protection device more universal. Dynamic simulation results show that the proposed method is not affected by the installation site of transformer in the substation; it can be ensured that the transformer can be reliably and rapidly switched off while transformer internal fault occurs, and the proposed method is enough sensitive to slight fault.