超高压输电线路的发展性故障判别元件

为提高发展性故障时保护装置的动作性能，该文提出了一种适用于电力系统超高压输电线路的发展性故障判别元件。当系统发生单相接地故障时，零、负序电流之间的相位关系和幅值关系是基本不变的，而发生发展性故障后，他们会有较大的变化，文中以此来构成发展性故障判别元件。与目前所用的判别元件相比，该元件不需要采用浮动门槛，动作灵敏度较高，不受电力系统振荡的影响,能更准确有效地判断出系统是否发生了发展性故障。非全相运行期间发生故障时，不论系统振荡与否，该判别元件都能准确地判断出来。离线数字仿真和动模试验验证了该判别元件的准确性。

An Evolved Fault Criterion for UHV Transmission Line Protective Relaying

In order to improving the performance of the relay devices during evolved faults, an evolved fault criterion used in power system UHV transmission lines is proposed in this paper. The phase-angle and the amplitude of are fixed values when a single-phase fault occurs, and they will greatly change after evolved faults occur. Based on the above characteristic, evolved faults can be detected. The sensitivity of the proposed criterion is higher than that of the quondam criterion, and no floating threshold is used. It can judge the evolved fault quickly and correctly whether the power systems swing or not. It can also work correctly if any fault occurs during two-phase operating conditions. Off-line tests and dynamic simulations on physical models confirm that the criterion is effective and valuable in transmission line protection.