Under frequency load shedding threats in island operation

Island operation possibility plays nowadays an important role in the view of preserving a part of the power system working during close-to-blackout emergency states such as collapsing power system divided in to smaller parts. Unfortunately following paper shows that not all regulation tools available for the transmission system operator (TSO) which are secured by the national grid code might be used during the island operation (respectively speed control mode of the power sources) for the same purpose of preventing frequency collapse. Under Frequency Load Shedding (ULFS) might cause an automatic disconnection of the working power station. This topic is demonstrated on an example system (city of Pilsen) on reality based input data. In the end the question of further research and solutions are discussed.