一种基于固有频率的超高压线路相间保护方案

在分析影响固有频率因素的基础上，提出了一种利用固有频率的超高压输电线路相间故障保护方案。理论分析表明，故障后产生的各种频率信号中，固有频率信号是明确的，且信号较强，便于采集。该方案利用线路两侧的固有频率主频差和阻抗判据区分区内、外相间故障，可以有效提高区内故障时保护的动作速度，同时保证区外故障时保护不误动。该方案不受系统振荡、负荷电流、故障时刻、过渡电阻、故障点位置和系统运行方式的影响，受电流互感器饱和的影响较小。ATP仿真和MATLAB分析验证了该方案的有效性。

Phase-to-phase Protection Scheme of EHV Transmission Lines Based on Nature Frequencies

Based on the analysis of the factors that affect system nature frequencies, a protection scheme based on nature frequencies is proposed. It is analyzed that the nature frequencies exist in fault component besides power frequency and the energy is strong and easy to sample. For phase-to-phase faults, the differences of nature frequencies at two ends of transmission lines and the impedance criterion are used to identify internal and external faults. Compared to conventional protection schemes, this scheme can decrease action time for internal fault. The scheme is immune to system oscillations, load current, fault time, transient resistance, fault location and mode of operation. Moreover, the current transformer saturation has less influence on the scheme. ATP simulation and MATLAB analysis verify the effectiveness of the scheme.