Numerical model of three-phase transformer banks and a shell-type transformer for calculating the transient current

Measurements of transient inrush currents in three-phase transformers offer important data for power system operation and protection. Because three-phase transformers are more widely used in industrial applications than are single-phase transformers, the inrush current of the three-phase transformer is worthy of investigation. Therefore, a method for accurately predicting transient inrush currents is useful in system operation and protection. This paper proposes a simple method, extended from single-phase transformers, to investigate three-phase transformer inrush currents. Various structures of three-phase transformers, including winding connections and loading conditions, are discussed. The simulation results are compared with experimental results. The proposed method is simple and effective for transformer banks and a shell-type (five-limb) transformer.