电流二次回路缺陷造成线路保护误动作分析及防范措施

国内多次发生因电流二次回路缺陷造成的线路保护误动作。通过分析其他设备电流二次回路的开路、短路而导致连接于同一电流二次回路的线路差动保护误动作、零序保护误动作等典型案例，指出目前串接故障录波及行波测距装置的做法增加线路保护电流二次回路复杂性，降低线路保护运行可靠性，存在导致所接入多套保护同时误动作的风险。为此，提出线路保护应采用专用电流二次回路，与其他二次设备分开，分别引入2组断路器电流以简化二次接线并减少外来干扰。同时，结合电网发展要求提出在现有二次绕组基础上增加1组5P级绕组并对各绕组分配使用进行了优化。文中所提方法已在西北750 kV电网建设和运行中获得应用。

Analysis and Countermeasures for Line Protection Mal-operation Caused by Current Secondary Circuit Defects

The line protection mal-operation caused by current secondary circuit defects has taken place many times in China. By analyzing two typical cases of the line differential protection and zero-sequence protection mal-operations caused by the open circuit and short circuit of current secondary circuit of other devices which are connected to the line protection current circuit, it is pointed out that the practice of connecting other devices with the line protection current circuit in series increases the complexity of the whole current circuit. The reliability of line protection operation is reduced, and there is a risk of simultaneous mal-operations of multiple sets of protections connected to the same current circuit. In order to simplify the secondary current circuit wiring and reduce external interference, it is proposed that line protection should use a dedicated current circuit, which is separated from other devices, and two circuit breaker currents are separately introduced to the line protection. At the same time, combined with the development requirements of power grid, it is proposed to add one set of 5P current windings to the existing windings and optimize the distribution and use of each current winding. The proposed method has been applied in the construction and operation of 750 kV power grid in Northwest China.