Protective Scheme Design for the Autonomous Operation of a Petroleum Refinery Cogeneration Plant

This paper presents the design of tie lines tripping to enhance power system stability for a large industrial customer with cogeneration units. The mathematical models with the corresponding parameters of generation units, excitation systems, governor systems and loads have been identified and verified. To enhance the system stability, the protective scheme by including the directional over current relay, under voltage relay and under frequency relay with proper settings has been applied. Three various external fault cases have been selected to verify the accuracy and effectiveness of the proposed schemes. It is concluded that the system stability of the industrial customer can be improved by the proper design of protective scheme.