The disconnect is open. You can see the air gap between the blade and the jaw, and the crew is geared up and ready to start. Before you read on, decide the one step that has to happen next, before anyone touches the conductor.
The instinct is to call it dead because you can see the gap. That instinct gets people killed. A visible open tells you the blade moved. It does not tell you what the conductor is carrying. Induced voltage from a parallel circuit, backfeed from a customer generator, or a trapped capacitive charge can keep that “open” line live. Tested in the field, a line that looks dead can still read 6 kV.
So de-energizing is not a single act, it is a sequence: open, lock, tag, then test for absence of voltage. You open the disconnect, lock it so no one can reclose it, tag it so everyone on site knows why it is locked, and only then do you test the conductor to prove it is dead. A visible open switch is not proof a line is dead. The test is.
The test only counts if the tester counts. You verify it live-dead-live: prove the tester on a known live source, test the line for absence of voltage, then re-prove the tester on that known live source. If the tester reads dead but fails the second proof, the dead reading is void and you start over. A tester that quietly died between the first proof and the line read would otherwise hand you a false dead on a live conductor.
Lock and tag protect the switch from being reclosed while you work. The test protects you from everything the open switch cannot see. Skip it and the whole sequence is theater, because the only step that proves the conductor is dead is the one you skipped.
Arc-flash incident patterns and OSHA enforcement shift with equipment age and grid modernization pace. The Feeder covers the field-safety and workforce signals that affect crew staffing and training budgets, free, every week.