From a Single 500 kV Alarm to a Deeper Design Question During commissioning on a 500 kV transmission project in 2024, a disturbance recorder captured something protection engineers never ignore: at the exact moment a test block handle was pulled quickly, the CT secondary circuit showed a transient open-circuit condition and raised an alarm. The team did what any good commissioning crew would do: Check wiring Check terminal torque Check device contact resistance The surprise c