In order to solve the problem of misjudgment in the flow transferring overload identification of protection-load shedding when the power swing occurs, this paper specifically analyses the electrical characteristics of the overload, the power swings and the fault to identify the differences among the three characteristics in measured impedance angle, measuring the rate of change in impedance, sequence component, and protection action situations, formulating a new flow transferring overload identification method. After starting backup protection, firstly it can distinguish failure with sequence component and protection action situation, then distinguish overload and swings with the rate of change in impedance; or firstly distinguish swings with the rate of change in impedance, then discern overload and fault with measured impedance angle. Example analysis results show that it can identify the overload and prevent a misjudgment when the system occur power swings, proving the correctness and validity of the method.