Which sequence correctly describes the proper de-energize, lock out, test, and ground procedure for a unit substation?

• A. Create a job plan; Shed load; Open LBF; Open ACBs; Lock out; Test; Ground primary; Ground secondary.
• B. Create a job plan; Shed load / turn off loads; Open ACBs (lock out); Open LBF (main); Lock out; Test; Ground out primary side; Ground out secondary side.
• C. Create a job plan; Open ACBs; Shed load; Lock out; Test; Ground; Ground.
• D. Create a job plan; Shed load; Open ACBs (lock out); Open LBF (main); Lock out; Test; Ground out primary side; Ground out secondary side.

Answer: (D)

The sequence tests safe shutdown and lockout practices around a unit substation. The first priority is to remove all energy from the equipment by shedding the load, so nothing is still energized when you start work. After the load is shed, you isolate the unit from its energy sources by opening the upstream protective devices (the ACBs) and applying lockout to prevent re-energization. Only after those sources are isolated do you open the main load-break path (the LBF) to fully disconnect the unit from the system, and you apply lockout there as well to ensure it cannot be re-energized. With the circuit isolated, you verify there is no voltage present using proper testing. Finally, you ground both the primary and the secondary sides to discharge any stored or induced energy, protecting personnel from shock and ensuring a safe working environment.

This ordering—shed load first, then isolate with upstream breakers and lockout, then open the main switch, lock out, test for absence of voltage, and finally ground both sides—matches best practice for de-energize, lock out, test, and ground in a unit substation. The other sequences either skip shedding the load, bypass a proper lockout, or perform testing before complete isolation or grounding, which increases risk.