By analyzing the current phase compensation method from delta to star connection， it is showed that the compensated differential current cannot reflect the characteristics of magnetizing current， when a transformer is energized. Furthermore， using the Matlab power system toolbox to simulate the magnetizing inrush current when a transformer YN，d11 switching on without load， the effects of two kinds of current phase compensation methods， from delta to star and from star to delta connection， on the ratio of second harmonic based scheme against the inrush current are compared. The calculation results show that the former has no advantage over the later on distinguishing the inrush， and split-phase blocking the differential should not be adopted for all of them. The cause of symmetric inrush is analyzed， and the simulation results show that the ratio of second harmonic in the symmetric inrush is not lower than that in the asymmetric inrush. Based on the comparison， the reliability of blocking scheme is improved by using the phase current without compensation to calculate the ratio of second harmonic. Furthermore it is proposed that using the comprehensive ratio of second harmonic to block the differential protection in all-phase and the open scheme to open the protection after a time delay can improve the operation speed of protection when the transformer is switched on with a short-circuit fault.