智能变电站保护用电流互感器配置问题及解决措施

通过一起断路器内部故障相关保护动作行为的分析,指出现有智能变电站保护用电流互感器配置方案存在严重缺陷。当一台保护停运时在断路器内部故障会出现快速保护死区,需要依靠带延时的失灵保护切除故障;而失灵保护会由于感受不到故障电流而拒动,从而威胁电网的安全稳定运行。为此,从工程设计上提出在每台断路器两侧各装设2组TPY绕组和1组5P绕组的保护用电流互感器配置方案,以彻底消除保护死区。同时,还从系统运行及保护配置等方面提出了补救措施,包括停用相关断路器及装设死区保护或改造失灵保护等。上述方法目前已在西北750 kV智能变电站建设和运行中获得应用,提高了保护的可靠性和系统的稳定性。

Problems and solutions of configuration scheme of current transformer used by protection in smart substation

The protection behavior in a circuit breaker fault is analyzed, and it shows that there are serious defects in the configuration scheme of current transformer used by protection in smart substation. When a set of protection is out of operation, the protection dead-zone will occur and the removal of fault is heavily dependent on breaker failure protection with time delay. Worse still, the breaker failure protection will fail to operate because the fault current can not be detected correctly, which severely threatens to the security of the power system. To solve this problem, a novel configuration scheme of current transformer with two TPY coils and one P coil in every break is proposed from engineering design to eliminate the protection dead zone thoroughly. In addition, remedial measures such as disconnecting the associated breakers from system operation and installing dead-zone protection or modifying breaker failure protection from protection configuration are also put forward. These solutions have been successfully applied to the construction and operation of 750 kV smart substations in Northwest Power Grid of China, which improves the protection reliability and system stability.