潮流转移过负荷识别新方案

为了解决现阶段保护减载的潮流转移过负荷识别环节在系统振荡时发生误判的问题，详细研究了系统振荡对潮流转移过负荷识别的影响，分析了过负荷、系统振荡和故障的特点，根据三者之间测量阻抗角、测量阻抗变化率、电流序分量及保护动作情况的差异，提出了潮流转移过负荷识别新方案。即在后备保护启动后，先根据电流序分量的特征和保护II段动作情况区分出故障，再利用测量阻抗变化率的特征，区分过负荷和系统振荡；或者先根据测量阻抗变化率的特征区分出系统振荡，再利用测量阻抗角的特征，区分过负荷和故障。算例分析结果表明，潮流转移过负荷识别新方案能够有效识别出过负荷，并可以防止系统振荡时的误判，证明了该方案的正确性和有效性。

A new program of flow transferring overload identification

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.