This paper explains a new, earth fault-sensitive algorithm for the longitudinal differential protection of transmission lines. The sensitivity of longitudinal differential protection in radial networks was examined. In particular, problems which can influence the protection’s speed and reliability were considered, such as great line length and the presence of resistance at fault position. In addition, the algorithm was tested for isolated and low-impedance earthed networks. The paper’s thesis is that rather than the stabilization current, the direction of the zero-sequence currents brought to the relay should be used. The zero-sequence currents’ direction is identified without using any voltage inputs. The suggested algorithm was compared to algorithms used by renowned relay manufacturers. Various types of external and internal faults were simulated. The results prove that the described algorithm is prompt and highly reliable under all the aforementioned conditions which can cause unwanted irregularities in the operation of the longitudinal differential protection.

中文翻译：

---

输电线路零序纵向差动保护

本文解释了一种用于输电线路纵向差动保护的新的接地故障敏感算法。研究了径向网络中纵向差动保护的灵敏度。特别考虑了线路长度过长、故障位置存在电阻等影响保护速度和可靠性的问题。此外，该算法还针对隔离和低阻抗接地网络进行了测试。该论文的论点是，应该使用引入继电器的零序电流的方向，而不是稳定电流。无需使用任何电压输入即可识别零序电流的方向。建议的算法与著名继电器制造商使用的算法进行了比较。模拟了各种类型的外部和内部故障。结果证明，在所有上述可能导致纵向差动保护运行不规则的情况下，所描述的算法是迅速且高度可靠的。