Your maintenance technician needs to add some wiring to the MCC, but since you have an older facility, the main power switch is not immediately in sight. Though the three-phase power is shut off and has a lock-out, tag-out notice placed on it, the cabinet should still be checked to make sure it is no longer live. NFPA 70E requires that workers verify equipment is in an electrically safe state before working on it. Until proven otherwise, equipment must be treated as energized, and necessary precautions must be observed.
To verify the equipment is in an electrically safe state requires a test for the absence of voltage (AoV). That process requires opening the cabinet and then following several prescribed steps with a digital multimeter—often a tedious and not exactly safe process. Wouldn’t it be nice to know, before opening the door, the power has been completely removed?