Large-scale integration of wind into power grids can have significant impact on the system stability. This paper presents the Rate Of Change Of Frequency (RoCoF) metric to determine limitations of the system with high levels of wind pene tration. The metric takes into account the system inertia, wind turbine response, and the size of contingencies. The metric is then applied to the Tasmanian power system -a small predominantly hydro power system with a potentially large-scale penetration of wind. The simulation studies are carried out using PSS/E. Case studies are performed with critical contingencies such as the loss of synchronous generation, loss of wind generation and loss of the HVDC interconnector, and their impacts are discussed.