不 依 赖 电 源 特 性 的 交 流 线 路 单 端 量 保 护

The existing AC line protection methods are still based on the characteristics of synchronous generator. As the proportion of renewable energy continues to increase and the characteristics of power electronics become more obvious, its adaptation boundary will gradually decrease. It is necessary to study new principles of relay protection that are independent of power source characteristics. The principle of using traveling wavefront fault information to achieve high-performance protection is proposed. Firstly, an analytical expression for the traveling wavefront of AC line faults is derived, indicating that the traveling wavefront expression includes the power frequency sine term and the DC attenuation term. The exponential coefficient of the DC attenuation term is only affected by the fault distance, while the amplitude coefficients of the two algebraic terms are related to the severity of the fault. Thereby the representation and decoupling of fault distance and fault severity information are realized. A wavefront exponential coefficient extraction algorithm based on the multi-point elimination is further proposed, achieving effective extraction of wavefront fault distance information. On this basis, a new principle of single-ended wavefront protection for AC transmission lines is proposed, and the influence of series/parallel/combination line boundaries on the wavefront exponential coefficient is analyzed. The simulation results show that the protection can quickly, reliably, and sensitively identify AC transmission line faults, without being affected by fault types and transition resistors. It is suitable for different scenarios of renewable energy and power electronic equipment integration, and has low computational complexity and is less affected by noise.