During the last decades, insufficient investment along with an increase in power demand have caused power system operating points to get closer to their stability boundary. In this condition, the need to fast and precise assessment of system stability status and proper execution of remedial actions results in a tendency of dispatching centres towards special protection system (SPS). This system is a smart monitoring and control system which detects the predefined condition and automatically executes pre-specified remedial actions to improve system stability. Indeed, such system can reduce human faults and prevent economic loss. Power management system (PMS) is a kind of SPS which is usually implemented in industrial power plants to intelligently manage remote devices and perform required actions against system contingency, especially in islanding condition. PMS has significant functions such as load shedding/sharing, generation shedding, generation mode control and import/export control to the control voltage, frequency and active/reactive power of the system. In this chapter, PMS configuration and its major functions are explained, and its impact on system stability is analysed through detailed dynamic simulations in DIgSILENT PowerFactory software. In these simulations, DIgSILENT simulation language (DSL) is used to model turbine-governor, excitation system and signals.