Analysis And Research Of The Transformer Inrush Current And The Sympathetic Inrush Current

Inrush current has been a reason which infects the correct operation of the transformer differential protection. For 3 phase transformers, the using of different current compensation methods will differ the characteristics of 3 phase inrush current. Then combined with the mechanism of inrush current, the effects of current compensation methods on the ratio of second harmonic based scheme against the inrush current are researched. Then the new current phase compensation method is improved by using the phase current without compensation to calculate the ratio of second harmonic, and solve the problem occurring in the new method. These years, there are instances of sympathetic inrush resulting in the malfunction of transformers'differential protection and back-up protection. In the thesis, by analyzing the mechanism and characteristics of sympathetic inrush, we make a systematic study on the infection to the back-up protection and other relative protection in the parallel connection, and we analyze the causes of the malfunction of protection. Several relevant methods for the operation are presented.