Dynamic analysis of transition into island conditions of Slovenian power system applying underfrequency load shedding scheme

Electricity blackout can be treated as critical situation of any country in economical, political, and security point of view. Therefore, underfrequency load shedding is one of the most important protection systems, as in many cases it is the last measure for preventing system blackout after serious disturbances occur in the power system. First, the static analysis of Slovenian power system has been performed to determine most probable islands in Slovenian system. Next, the dynamic analysis of one of these islands has shown, that the frequency gradient alone can give very misleading information about the active power deficit in an island. Several other variables must also be taken into account. Finally, a draft of a gradient based underfrequency load shedding scheme is presented, which highlights the gradient use problems and shows the potential of considering second frequency gradient as an indication of turbine governor response.