Power system restoration in large cities

This paper presents initial results of a grid restoration study carried out in the cities of Berlin and Hamburg. The objective of the study was to identify the optimal restoration strategy for the local distribution network by using only units available within the service areas. By putting the strategy into practice, partial restoration can be achieved faster and the cities are not totally dependent on the restoration process taking place outside their purview. Distinctive steps of the restoration process have been tested using dynamic simulations taking into account the existing grid topology and using realistic dynamic models of the power units. Field tests are carried out to verify the simulation results and also for testing the most crucial restoration steps. The authors give an account of their experience including some recommendations pertaining to grid restoration in large metropolitan areas in general.