科研之友
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摘要
The transformer differential protection may occur maloperations due to the non-linearization of the core of transformer during transient. It will be of great benefit to the improvement of the operation and design level of transformer protection if these maloperations can be correctly analyzed and described. A two-order equivalent circuit based model of transformer switching-in with load is proposed to investigate the maloperation of transformer protection during the transient induced by loaded transformer switching-in or the isolation of the external faults. It is pointed out that the main flux of the transformer may consist of two exponentially decaying DC components with different time constants and signs. The flux with higher time constant possibly keeps quite high residual magnitude after the other one decay sufficiently. Therefore, the core of the transformer will saturate seriously and the characteristics of the inrushes will vanish accordingly. Under this circumstance, any differential protection using characteristics of inrush as restraint criterion is possible to cause maloperations. The presented work will benefit to the reinforcement of the transformer protection theory.
- 出版日期2003
