摘要
随着变压器铁心材料的改进,饱和磁通逐渐降低,励磁涌流中的二次谐波含量随之降低,这给以二次谐波闭锁判据为原理的差动保护算法提出了挑战。极端条件下,三相励磁涌流二次谐波含量均会低于门槛值,对任何一种出口方式,二次谐波闭锁判据都会开放差动保护。针对由不对称的励磁涌流产生的零序电流中谐波含量较高这一特点,提出以星形侧零序电流二次谐波含量为核心设计的励磁涌流识别算法。比较于以前的算法,所提出的算法可以快速识别励磁涌流,能够适应由并联电容器导致的短路电流波形畸变。仿真实验验证了算法的可行性,在正常剩磁条件下,变压器三相励磁涌流二次谐波含量均低于门槛值时,算法能够正确闭锁差动保护;当变压器低压侧接有并联电容器且发生区内故障时,差动保护能够无延时出口跳闸。
With the improvement of transformer core material,the saturated flux decreases gradually and the second harmonic content in inrush current decreases accordingly,which challenges the differential protection algorithm based on the second harmonic blocking criterion.Under extreme conditions,the second harmonic content of three-phase inrush current will be lower than the threshold value,regardless of the outlet mode,and the second harmonic blocking criterion will start differential protection.Aiming at the characteristic of higher harmonic content in zero-sequence current generated by asymmetric inrush current,this paper proposes an algorithm for identifying inrush current based on the second harmonic content of zero-sequence current on star-side.Compared with previous algorithms,the algorithm proposed in this paper can identify inrush current quickly and adapt to short circuit current waveform distortion caused by shunt capacitors.The feasibility of the algorithm is verified by simulation experiments.Under normal residual magnetic condition,when the second hannonic content of three-phase inrush current of transformer is lower than the threshold value,the algorithm can correctly block differential protection;when the transformer is connected with shunt capacitors at low voltage side and internal fault occurs,differential protection can trip out without delay.
作者
谢广宇
孙向飞
林湘
XIE Guangyu;SUN Xiangfei;LIN Xiang(Faculty of Electric Power Engineering,Kunming University of Science and Technology,Kunming 650500,China)
出处
《电力科学与工程》
2019年第12期14-21,共8页
Electric Power Science and Engineering
关键词
变压器
励磁涌流
差动保护
零序电流
transformer
inrush current
differential protection
zero-sequence current
