The outflow current during an internal fault on the busbur will decrease the sensitivity of the relays for the overall differential element and even lead to operation refusal or trip time delay for the total protection, this paper adopts a new busbar protection method of the virtual voltage phase difference of the fault component. This method extracts the key data for judging faults inside and outside the fault component stably by shifting the position of the fault component voltage signal, so as to obtain the virtual voltage phase difference of the fault component: when there is a fault in the area, the virtual voltage phase difference of the fault component tends to 180°, when the fault occurs outside the area, the phase difference of the virtual voltage of the fault component tends to 0°. Finally, it is verified that the new method is not affected by the outflow current of the busbar internal fault, and its sensitivity is at least 1.1 times higher than that of the ratio differential protection through theoretical analysis and EMTP to build the Laxiwa hydropower station model. Through the analysis and simulation of the parallelogram rule, it is verified that the new method is not affected by the high impedance grounding of the fault in the busbar area; and the method has strong anti-current transformer saturation ability.