In an industrial setting a PLC is not simply "plugged into a wall socket". The electrical design for each machine must include at least the following components.

transformers - to step down AC supply voltages to lower levels

power contacts - to manually enable/disable power to the machine with e-stop buttons

terminals - to connect devices

fuses or breakers - will cause power to fail if too much current is drawn

grounding - to provide a path for current to flow when there is an electrical fault

enclosure - to protect the equipment, and users from accidental contact