Abstract: A reversed feeding fault from secondary to primary circuit in the medium pressure switch No.2 main transformet of Chapeng Substation at turn on operation was analyzed. The reason of the reversed feeding fault was found, and the dangers of the fault to system were expounded. Aiming at the defect of feeding operation, some improvement measures were proposed for the elated technician referring.

Key words: reversed feeding, loading through by-pass bus, secondary voltage