L90光纤差动保护误动原因分析

光纤差动保护由于动作速度快，选相方便而在短线路保护中大量应用，华能德州电厂采用了GE公司生产的L90光纤差动保护，但此保护在变压器空投时出现误动。介绍了差动保护原理和L90光纤差动保护构成．并结合保护原理及现场实验情况进行了分析，通过小矢量算法和傅里叶算法的比较及对变压器励磁涌流的录波分析，认为保护误动源于电流互感器(TA)选取不当导致算法滤波特性不佳而产生的差流。最后，结合现场实际情况提出了解决问题的方案。

Analysis of L 90 fiber optical differential protection misoperation

Fiber optical differential protection is widely used in short line owing to its quick action and easy phase-selection. L 90 fiber optical differential protection of GE is adopted by Huaneng Dezhou electric power plant . But it operates improperly when transformer is tested in no load states. The principle of differential protection and the composition of L 90 fiber optical protec-tion are introduced. With the comparison between Phaselet algorithm and Fourier algorithm and the waveform analysis of excitation surge current,it is concluded that the badly selected CT parameter causes the bad transient performance of the algorithm,which generates the differential current. A solution to this problem is proposed.