This paper analyzes the relations between the phases and value of voltage at the high voltage side and low voltage side in the phase B connecting the ground system.

A generator-transformer differential protection using TA at the low voltage side of the auxiliary transformer is designed according to the four principles usually, but the sensitivity of the differential protection can not meet the requirement when the fault occurs at the Low TA internal of the protection scope.

A structure with dynamically controlled anode short is brought forward,and can be used in the low side device of power IC with high side and low side drive and half bridge output section.