Research on Principle and Countermeasures of the Transformer Sympathetic Inrush

Based on the analysis of sympathetic inrush in no-load parallel transformer, the principle and characteristics of sympathetic inrush are studied according to flux variation. Time differential method is analyzed to identify sympathetic inrush .The influencing factors of sympathetic inrush are studied. The points are verified by MATLAB simulation. The harm of sympathetic inrush to transformer differential protection and back-up protection are discussed, and several countermeasures to sympathetic inrush are presented.