I've just had a holiday lights company install some outside tree lights, and I found they had done it so that at several places the prongs of mains cable plugs had been left exposed, and carrying mains voltage. I've put a couple of pictures here: https://tinyurl.com/tk-wiring-pics (In the one with the voltmeter, that plug is just as it was left lying on the grass by the installer -- I didn't have to unplug it to get to the pins.)
Is that permitted under the US NEC?
I know there is provision in the NEC for temporary (up to 90 days) installations, and the installer has told me that their setup is fine because of that. But that sounds a bit dubious if it implies you can leave 100V+ lying around in the grass for some kid to stand on.
Also, I think I found the reason it has happened, and that is that the installer has made up some of their own cables, and one of them has a plug at both ends (i.e. instead of a plug at one, and a socket at the other). As a result they have in a sense "reversed the direction" of plug-to-socket, and so instead of the usual power going into plugs and out of sockets, they have a big section of our yard lights where power is going into sockets and out of plugs (several of which are then exposed to the outside).
Seems very unsafe to me but, again, is that actually allowed by NEC under the temporary installation allowances?