中文摘要：

可靠地判别断路器合闸时输电线路是否有故障，是超高速保护实用化必须解决的一个棘手问题。文中指出，可将其归结为空载合闸于故障线路的识别问题。合闸于正常线路与故障线路存在时域、频域的特征差异：一方面，初始前、反行波到达保护安装处的时间间隔和它们之间的极性关系都明显不同，并特别分析了三相系统中模量前、反行波的极性关系与单相系统中的极性关系并不完全一致；另一方面，合闸后暂态电压中自振荡频率的含量也显著不同。据此，提出合闸于故障线路的识别原理及其利用小波变换的实用算法，大量ATP仿真表明该识别原理可行、算法快速可靠，将有助于进一步提高超高速保护的性能。

英文摘要：

It is vital but difficult for ultra-high-speed （UHS） protection to reliably identify whether there is a line fault when a circuit breaker closes into a transmission line. This paper firstly indicates that circuit breaker closure can be simplified to unloaded closure for UHS protection. Then the paper analyzes the different features of the circuit breaker switching into a normal or faulted line. On one hand, the difference lies in the arriving interval and polarity relation between initial forward and backward traveling waves at protection location. On the other hand, the difference also lies in the voltage/current self-oscillating features. Besides, the different polarity relations of initial forward and backward traveling waves are discussed respectively in phase domain and modal domain. Based on these different features, the paper proposes the discriminating approach of circuit breaker switching into faulted lines, and presents the corresponding discriminating algorithm based on wavelet transform. ATP simulation tests show that this approach is feasible and reliable.