Power management system (PMS) which is a kind of special protection system is used to detect predefined conditions and execute timely remedial actions to prevent instability or improve operating point, especially in an islanded system. To this purpose, PMS usually includes several functions such as load shedding/sharing, generation shedding, and generation mode control which are automatically executed to improve operating point. In this chapter, to show the capability of DIgSILENT power factory to simulate smart grids functionalities, DIgSILENT programming language (DPL) is used to model PMS logic in automatically detecting islanding condition as well as executing load/generation shedding in an islanded system to prevent instability. Indeed, this modelling gives the possibility to check the impact of considered PMS logic under different operating conditions on the stability of the system.