Calculation Method Based on Analytical Formulas for Inrush Currents and Voltage Dips of Three-Phase Transformers: Energization from Delta-connected Side

A method has been developed to calculate the inrush currents and voltage dips during transformer energization with the same accuracy as electromagnetic transient (EMT) analysis. The developed method is based on analytical formulas obtained by directly solving the circuit equations formulated by simplifying the power system and transformer circuit. The calculation results of inrush currents and voltage dips under severe conditions are compared with EMT analysis results and confirmed to be in good agreement.