Enhancing Power Grid Stability: Design and Integration of a Fast Bus Tripping System in Protection Relays

This article introduces a novel method for efficiently and promptly operating protection relays within a power system, with a specific emphasis on adaptive overcurrent (OC) protection in a power grid. The approach utilizes SEL751 and SEL751A relays that communicate through the IEC-61850 GOOSE protocol, establishing connections using intelligent electronic devices (IED) at several locations in the system. The power system, consisting of transformers, bus bars, and feeders, employs protection relays to identify OC faults based on time and current parameters. Relay configurations are tested in a case study at the Omicron Lab involving a 138/25kV substation. The test encompasses various fault scenarios on the low-voltage (LV) and high-voltage (HV) sides, incorporating different current values and fault times, utilizing the chosen time-overcurrent U3 (very inverse) curve. The proposed approach exhibits the ability to promptly remove faults in transformers and substations at both the HV and the LV levels. Furthermore, the experimental results closely match the theoretical calculations, validating the effectiveness of the proposed approach in the protection of AC grids. Additionally, built-in cybersecurity measures in SEL relays ensure secure and reliable operation, mitigating the risks of cyber-related relay failures.