Detection Method of Transformer Inrush Current based on Estimated Parameters of Transformer Equivalent Circuit

Protection relays are used to ensure stable and efficient operation of the transformer. Protection relays detects the transformer fault and remove the fault point rapidly. However, there is a possibility that the transformer inrush current causes the maloperation of protection relay. Therefore, it is necessary to detect the inrush current instantaneously. This paper proposes a method for detecting transformer inrush current based on equivalent circuit parameter of transformer. This method estimates transformer equivalent circuit parameters from voltage and current waveforms using z-transform. The proposed method has the ability to detect inrush current faster and less computational complexity than conventional methods. To evaluate the theoretical principles of the proposed method, numerical simulation using MATLAB are performed. In addition, the proposed method is verified experimentally for a single-phase transformer.