Técnicas para disparo de ilhamento em sistemas elétricos industriais com geração própria

Abstract

This dissertation presents a comprehensive analysis of islanding protection strategies implemented in industrial power systems with on-site generation, focusing on a petroleum refining unit. The study addresses islanding detection techniques, connection protection schemes, and load shedding systems, aiming to ensure the continuity and safety of the power supply. The research is centered on two pillars that bring substantial benefits to the production process. The first pillar is islanding. If islanding protection is properly tuned, its operation can be delayed as much as possible to avoid unnecessary disconnection and the associated load shedding. The second pillar is load rejection and shedding. In the event of an islanding situation, if the load rejection and shedding scheme is able to maintain the balance between loads and generation in the power system, a blackout can be avoided. A case study, using a real system belonging to a major Brazilian oil refinery, was used in the development of the research. The models used to represent the refinery’s electrical system were described and validated through real tests. Records of actual disturbances in the utility power system were used to support the analyses. Finally, simulations were performed in ANATEM to estimate the system behavior under typical disturbances and to verify the adequacy of the islanding protection and load shedding settings implemented for the plant. The results show that the implemented islanding protection provides appropriate sensitivity, ensuring stability and protection of the industrial electrical system under disturbance scenarios in the grid. The load rejection and shedding system also showed satisfactory performance by successfully restoring the balance between load and generation after the islanding process. The study also identified improvement opportunities for these systems. For the islanding protection, a setting change was identified that allows for maximizing the delay before islanding occurs, thus avoiding unnecessary disconnections. For the load shedding system, the installation of a backup scheme was recommended in case the main scheme fails, thereby increasing system reliability.