Firstly, it is demonstrated that thermal power OPC protection model needs to be considered in power system electromechanical transient simulation program. Then, the OPC protection mathematical model is built based on Power System Analysis Software Package (PSASP). Furthermore, the model is verified through dynamic simulation comparison of typical accidents in Northeast China Grid. Finally, combined with actual frequency stability cases of Northeast Power Grid, some relevant management suggestions and measures are put forward on OPC coordinated management between unit and grid. It can improve the success probability of islanding operation in local area power grid with large islanding operation risk, through adjusting the thermal power unit OPC protection action value, optimization of OPC protection strategy in system frequency rising and falling stage.