中文摘要：

在电力系统振荡期间，三相有功、无功的变化率分别是两侧系统功角的正弦和余弦函数，经过归一化后，理论上不可能同时低于0．7的门槛，而对称故障发生后，有功、无功的变化率都趋近于零。利用上述特征提出了基于功率变化率交叉闭锁振荡中对称故障的快速识别方法。通过修正后的2点采样值积算法，功率的计算不受频率变化的影响。作为一种积分型判据，其动作稳定性高。仿真结果表明：该方案具有较高的可靠性和速动性，最长动作延时为算法的数据窗长30ms。

英文摘要：

It is demonstrated in this paper that the change rate of the sum of three-phase active powers and reactive power are the cosine function and the sinusoidal function with respect to the phase difference between the two power systems during power swings. In this case, they cannot be lower than the threshold of 0,7 after they are normalized. However, they will level off to 0 when a three-phase fault occurs during power swings. Based on this analysis, a cross-blocking scheme to rapidly identify the symmetrical fault occurring during the power swings is therefore proposed. By virtue of the improved two-instantaneous-value-product algorithm, the calculation of the active and reactive power is immune to the variation of the system power frequency. As an integration based criterion, this criterion has high stability. Simulation results show that this scheme is of high reliability and fast time response. The longest time delay is up to 30ms.