Definition

Power Swing Blocking (PSB) is a protective scheme used in electrical power systems to prevent certain protective relays from operating during power swing conditions. A power swing is a temporary oscillation in system voltage and current that can occur following disturbances such as faults or sudden changes in electrical load. PSB schemes distinguish between power swings and actual fault conditions, temporarily blocking relay tripping during a detected power swing to prevent unnecessary disconnection of transmission lines. Once the power swing subsides, the protective relays return to normal operation.