This paper presents a practical new method to quickly and effectively eliminate coordination curve intersection problems in subtransmission systems resulting from improper protective coordination settings in electromechanical overcurrent relays. Firstly, a database representing the relay operating characteristics was constructed based on the electromechanical overcurrent relay characteristic curves published by the manufacturer. Then, combining with this database, a fixed-point coordination curve adjustment procedure dedicated to electromechanical overcurrent relays was proposed to tackle the curve intersection situation of the coordinated upstream and downstream relay pair appearing in the original design. In addition to correcting manmade errors that could cause unexpected widespread power outages when fault occurs, the proposed technique can also enhance the effectiveness and accuracy of coordination. This study also simulated an actual case in Taiwan Power Company to verify the feasibility and practicality of the proposed method.
