That is a fire (or electrical accident) waiting to happen. Nothing good can come of that. It is negligent and noncompliant and most definitely not normal. I'd imagine it wouldn't be a fun thing to try and explain to an insurance company either, in the event. I can imagine a dozen different scenarios in which that connection becomes a disaster either to uptime, property, or safety.
You need to disconnect the power above that connection immediately (eg. the other end of the cord). I personally wouldn't bother with an electrician just to unplug the other side of that, assuming the other side isn't just as much of an atrocity and also assuming that there isn't some other circumstance making that dangerous. If you want to be extra cautious (it never hurts), wear some electrically insulating gloves and get a voltage tester (designed to test for mains current) to ensure that the leads on the jerry-rigged side of that cable aren't live.
Once there isn't any current in that system, if you feel safe doing so, carefully remove those blade connectors (if they will slide off), or better still, remove the PDU from that environment and seperate the cable from the rest of the assembly elsewhere. Destroy the plug on the other side of that cable and throw it away. It's a great pity you can't track down whoever is responsible for it; they need a stern lecture from a fireman.
Absolutely do not leave this with current running through it! Can you imagine what might happen if a metal object were to fall in there, connecting that mounting rail to mains current, or something? Even if you cordon that thing off it's not safe.
Even supposing there was a thin coating of some insulating substance in there, that wouldn't be nearly enough to protect it from all the things that might occur.
It would be better for you to run without the redundant power source than for you to allow that to continue to exist in your environment. I would even sooner move the equipment to another rack (if that isn't a redundant PDU) than leave that in place.