Fuzzy Identification Method Of Transformer Inrush Current

With the increase application of large power transformer in power system, the transformer protection is required more reliability and higher speed. As one of the transformer primary protection, differential protection has the features of high mobility, high sensitivity, and selectivity.In this paper, the process of the inrush current generation is detailed analyzed. And some methods of identify the inrush current is discussed, such as the second harmonic restraint principle, the waveform symmetry principle, the intermittent angle principle and so on. Since each criterion has its own limitations, the multi-criteria fuzzy recognition used in this paper gives the membership to the criterion of the second harmonic, the waveform symmetry characteristic, and the intermittent angle characteristics; and identify the inrush current according to the weight and threshold which is discussed in this paper too.The criterion of fuzzy recognition adopted in this article considers the advantages and disadvantages of each criterion, and can identify the transformer inrush current effectively, which improves the transformer differential protection performance.