Good question! AC voltage is relatively safer because it crosses the zero point 120 times a second. If it passes through your body, your muscles will spasm but you will have an opportunity to pull away. Also, AC voltage will probably not sustain an arc at such a low voltage, again, because it is constantly switching polarity.
On the other hand DC voltage, once a connection has been made, will continue to flow through that path to complete the circuit. You can think of it as the electrons on the hot wire want very badly to get back to the place where they were generated (the source transformer under that covered up manhole). If they find a path through your body, it will continue to flow through your blood vessels until either you or the wire burns up, or the upstream transform faults. You basically become a fuse. If you are part of the circuit, you'd better hope there is somebody nearby to hit you you with a pole, because otherwise you are pretty much stuck that way. Also, DC voltage is much better at sustaining an arc, even below 100 volts, so it can set off an explosion that can ignite whatever dust is lying around the equipment. Google "arc flash" to see what this looks like.
> Also, DC voltage is much better at sustaining an arc, even below 100 volts, so it can set off an explosion that can ignite whatever dust is lying around the equipment
Ahh, that's what I was missing. I assume the "painted black" part was to insulate the box and mitigate this risk when the box was closed?
On the other hand DC voltage, once a connection has been made, will continue to flow through that path to complete the circuit. You can think of it as the electrons on the hot wire want very badly to get back to the place where they were generated (the source transformer under that covered up manhole). If they find a path through your body, it will continue to flow through your blood vessels until either you or the wire burns up, or the upstream transform faults. You basically become a fuse. If you are part of the circuit, you'd better hope there is somebody nearby to hit you you with a pole, because otherwise you are pretty much stuck that way. Also, DC voltage is much better at sustaining an arc, even below 100 volts, so it can set off an explosion that can ignite whatever dust is lying around the equipment. Google "arc flash" to see what this looks like.