纵联零序方向保护误动原因分析及其对策

在非全相运行期间,由于保护逻辑设置不当或通道等因素的影响,往往会导致高压输电线路纵联零序方向保护误动作。结合现场500kV电网中出现的某次故障事故,深入分析了事故中纵联零序方向保护误动作的原因:通信接口设备对允许信号的展宽;非全相运行时没有闭锁纵联零序保护。并详细描述了影响纵联零序方向保护正确动作的主要因素,有弱馈、非全相运行、分布电容、功率倒向、零序互感等。给出了防止纵联零序方向保护误动作的解决措施:非全相运行与零序功率倒向、逻辑的输出通过或门构成闭锁纵联零序保护;去掉接口装置对允许信号的展宽。现场运行结果证明了该解决措施的准确性和有效性。

Analysis of longitudinal zero sequence direction protection misoperation and its countermeasures

If the protective logic setting is incorrect or the communication channel wrong,the longitudinal zero sequence direction protection of high voltage transmission line will operate improperly under non-complete phase operating condition.With an accident in 500 kV power network,an improper operation of the longitudinal zero sequence direction protection is analyzed:the enable signal is extended by the communication interface device and the longitudinal zero sequence protection is not blocked under non-complete phase operation.The main factors causing its improper operation are described in detail,i.e.week feeding,non-complete operation,distributed capacitance,inverse power direction,zero sequence mutual inductance,etc..The countermeasures are put forward:blocking the longitudinal zero sequence direction,protection by the OR gate output of the non-complete operation signal and inverse zero sequence power signal;removing the interface device to prevent extension of enable signal.Site operation shows that proposed countermeasures are correct and effect.