Measures taken by a municipal energy utility to maintain supplies of energy in cases of frequency drop

A drop in power frequency indicates a deficiency of power in the grid. Attempts are made to offset this drop by means of graded measures ranging from warning staff and the use of all available power-generation reserves, to load-shedding. If, despite all counter-measures, the drop in frequency cannot be stopped and the probability of a total power failure arises, municipal or regional energy utilities with power-generation facilities close to their consumers can isolate themselves from the grid and thus create a grid island. Taking the Technische Werke der Stadt Stuttgart AG (TWS) as an example, the authors show how even stations further afield can be integrated into this grid island, which technical boundary conditions have to be observed when doing so, and how this concept was realized. They also look at the re-establishment of the grid subsequent to such a case of isolation, or even after a total power failure