Under frequency relay setting for tie line and load shedding of an industrial power system with multiple cogeneration units

This paper presents the enhancement of power system stability for a large industrial customer when a new cogeneration unit with 40 MW capacity has been added to the system. The proper settings of protective relays have been designed according to the transient stability analysis. For the severe nearby fault, the under frequency relay are applied for the isolation of the industrial power system and for the load shedding so that the tripping of the regeneration units can be prevented and the critical loads can be maintained. To verify the effectiveness of the proposed protective scheme, the computer simulation of the industrial power system under various load levels and fault cases has been performed. It is concluded that the system stability of the industrial customer can be improved by the proper design of protective schemes.