3/2接线电流互感器断线快速闭锁母差判据的研究

西北电网线路长,支路少,3/2接线系统实际投入运行的母线少,当电流互感器(current transformer,CT)断线和短路故障相继发生时间差在5 s内时,断线慢速闭锁差动判据由于5 s延时而不能闭锁CT断线而引起差动误动,针对该问题,分析了CT断线的典型特征,提出可以用差流上升、制动电流下降作为3/2断路器接线CT断线快速闭锁母线差动保护的判据、判据的3种情况及其实现。仿真验证表明,该判据在不影响差动保护快速性的同时,能有效地识别CT断线,进而闭锁母线差动保护,经多次静、动模试验验证,该判据能正确动作,可用于传统及数字化后的双母接线母线差动、变压器差动、发电机差动等电流差动保护。

Study on Rapid Interlock Busbar Differential Criterion for 3/2 Wiring CT Break Line

Circuits of northwestern power grid are long with few branches and busbar for practical operation of 3/2 wiring system are few, too. When current transformer break line and short circuit fault happening in succession within 5 seconds, for reason of 5 seconds delay, break line slow interlock differential criterion is not able to cause CT break line interlock which may result in differential misfunction. Aiming at the above problem, this paper analyzes typical characteristic of CT break line and proposes to take difference streak rise and braking current decrease as criterion for rapid interlock busbar dif- ferential protection for 3/2 breaker wiring CT break line. In addition, it proposes three conditions of the criterion and reali- zation ways. Simulation verification indicates that this criterion is able to effectively identify CT break line at the same time of not affecting rapidity of differential protection, and then it is able to interlock bus differential protection. By several times of testing and verification, it proves that the criterion is able to act correctly and used for current differential protec- tion such as traditional and after-digital double-bus wiring differential protection, transformer differential protection and generator differential protection.