Improve transient frequency response by adjusting generators´ over frequency relays

Defense plan strategies are designed to avoid major blackout in electrical power systems and to keep frequency and voltage of the system within the acceptable limits. In some cases, islanding occurs as a result of lines cascading tripping, which leads to an over frequency situation in excess generation areas. This paper introduces a control strategy to maintain the frequency of the system within the generation protection limits in the excess generation islands. This strategy adopts intentional time delay coordination for generators tripping time. A number of appropriate generators can be tripped to decrease the frequency of the islands. A partial blackout in the western area of Libyan network is taken as a real case study. NEPLAN program is used in this study to reconstruct the incident and evaluate the performance of the new strategy.