Protective relay setting of the tie line tripping and load shedding for the industrial power system

This paper presents the proper underfrequency relay settings to enhance the operation of industrial power systems with cogeneration facilities. A coge neration unit was installed in the plant in 1996 to supply the power demand of the plant. The cogeneration unit always faces the shutdown problem when a severe fault occurs on the nearby Taipower network. It is, therefore, ne cessary to investigate the plant protective relay settings to prevent a who le plant blackout when the contingency occurs, The transient stability anal ysis has been performed by considering both the detailed models of the coge nerators with the governor and exciter control systems and the external uti lity power system. The underfrequency relay settings for tie line tripping and load shedding are designed to prevent the tripping of the cogeneration units so that the electricity service to the critical loads of the industri al customer can be maintained in case serious external disturbances such as short circuit faults occur. In this study, the scheme of underfrequency re lay settings has been developed for the power system of a large synthetic r ubber manufacturer with a large cogeneration unit. Three study cases have b een selected for the transient stability analysis to verify the effectivene ss of the proposed protective relay setting.