一起变压器差动保护误动事故的分析和对策

Analysis of mal-operation of transformer differential protection

通过变压器空载合闸时差动保护误动事故的分析,对波形对称原理识别励磁涌流的能力作了进一步的分析和研究。研究表明,励磁涌流在间断角较小的情况下,采用分相制动的波形对称原理因波形对称度较好而导致差动保护误动。针对波形对称原理的特征,给出了四个应对策略,综合考虑差动保护的可靠性和安全性,建议波形对称原理采用"三取二"的闭锁方式。

Differential protection based on waveform symmetry is furtherly studied and analyzed through a mal-operation incident when the unloaded power transformer is Connected to the power system. Research shows that differential protection based on waveform symmetry and phase-braking scheme can make a mal-operation when current wave＇s dead angle is small and waveform is almost symmetrical. Four strategy methods are presented according to the characteristics of waveform symmetry. Considering reliability and security of differential protection, three-take-two braking scheme is suggested.