Enhancing Backup Protection of the Transmission Network Under Stressed Conditions

The complex operating modes of the power transmission network have inadvertently increased the vulnerability of relay mal-function due to stressed conditions such as load encroachment and power swing etc. These conditions can trigger cascading outages, posing significant challenges in maintaining grid stability. Unintended operations of distance relays have been identified as a major factor in cascading outages and significant power system blackouts. To address this, enhancing backup protection to detect these stressed conditions has therefore become a top priority. A proposed backup protection scheme for detecting stressed conditions leverages the Rate of Change of Impedance Angle (ROCOIA) and effectively differentiates between internal and external faults using the Super-Imposed Current Angle Difference (SICAD). In contrast to conventional protection relays that isolate faulted components, this backup scheme initiates corrective actions to stabilize the power system under stressed conditions. It also unblocks the distance relay during faults, thereby ensuring the overall integrity and reliability of the system across various stressed scenarios.