There are safety buses within onsite power systems in nuclear power plants as opposed to other power plants. The safety buses have a role of supplying vital power to essential loads and safety features for safety shutdown of nuclear reactor. If the essential loads and safety features become inoperable due to loss of power, the risk of nuclear power plants is increased. The power supply systems in nuclear power plants should be designed as a defence in depth to prevent loss of power supply to the safety features. The power transfer in nuclear power plants has a role of the first level design for the defence in depth of power supply systems. The power transfer in design of power systems enables to provide the reliable and stable power supply to onsite power bus. It is important to furnish the optimal power transfer scheme to prevent loss of power at onsite power bus and to minimize propagation of electrical faults. Therefore, this study performs that the significance for power transfer scheme considering bus electrical protection is analyzed by means of operating experience from recent event case in nuclear power plants.