Aiming at the tripping event of a power plant unit, the abnormal operation of power load unbalance protection is simulated and analyzed. According to the over-speed protection logic action record data, using the power system simulation software and large network data to simulation calculation according to several typical faults, provide the basis for setting the power load unbalance protection speed lockout setting. The simulation results show that adopting the 3030r/min as the power load unbalance protection can not only avoid the typical fault of the system, but also have little effect on the speed control of the unit when the load is applied.