Planning the islanding scheme of a regional power producer

A power system can be divided into islands in the case of serious system disturbances. The authors discuss the types of power system disturbances, methods available for system protection and especially strategies for controlling the underfrequency islanding and island operation. Dynamic simulation studies were made concerning three Finnish municipal energy utilities owning local power generation. The results are presented as general principles which aid any power producer in planning its islanding scheme. These include methods for selecting the island area and suitable load shedding and reactive power compensation practices for this area. In addition, the earth-fault relay coordination during the island operation is discussed