直阻试验后变压器差动保护误动分析

Analysis of a Mal-operation of Differential Protection After the DC Resistance Testing

直阻试验后变压器残余剩磁将影响变压器差动保护的判别,空投变压器时会产生数值较大、二次谐波含量比较低的励磁涌流,结果可能导致差动保护二次谐波闭锁失效。采取二次谐波、波形对称多种判据混合判别方法将提高差动保护动作的可靠性。针对直阻试验后,变压器空投造成的差动保护误动进行分析,比较二次谐波闭锁判据、波形对称闭锁判据在涌流识别上的差异。根据分析结果,提出为防止变压器差动保护误动应采取的可行措施。最后在不同剩磁模型下仿真空投涌流,通过不同剩磁下二次谐波含量与波形对称特性的数据对比,测试了几种涌流判据的有效性,验证了防止变压器差动保护误动措施的可行性。

After the DC resistance testing of a transformer, the residual magnetism will affect the judgement of transformer＇ s differential protection. Upon charging the transformer with no-load, large inrush current will be created with big magnitude and low harmonics, which may lead to the secondary harmonic blocking failure of differential protection. The combined judgement method of secondary harmonics and waveform symmetry will improve the reliability of the differential protection action. An analysis is conducted of the mal-operation of differential protection after the DC resistance testing, and the difference in identifying the inrush current is compared between the blocking criteria of secondary harmonics and waveform symmetry. Based on the analysis, some feasible measures are proposed to avoid the mal- operation of differential protection. At last, with different residual magnetism modeling, the different blocking methods are tested again.