Once upon a time, in the nuclear submarine navy, my shipmate tags out the ship's battery breaker. As part of the tagout, he checks that the ship's DC bus is deenergized - within the battery breaker box itself. During the check, he finds some voltage, which isn't entirely unexpected, since there is enough capacitance on the DC bus to hold it charged for a while. So he uses a specialized grounding probe - about 1/8" diameter copper rod with a reinforced handle - to discharge it. Unfortunately, he has misunderstood what was inside the breaker box and is actually shorting out the ship's main battery! This is a couple hundred volts DC, and a few thousand amp-hours of capacity, and it delivers enough current to instantly vaporized the grounding rod. He's knocked on his ass by the arc blast. Fortunately, he was correctly considering the box to be energized gear and was wearing a full set of PPE, suffering only minor flash damage to his eyes.