Use your hands to pull the black cylinder out from the center of the baseplate. This is the power coupling.

Take note of the arrangement of the wires on the coupling device to aid in reassembly. If desired, mark the wires and connectors with different colored tapes.

The GREEN wire is the 'ground' or 'protection' wire. It is connected to the center post.

The other two wires are both BLACK. You can distinguish them by feel:

The smooth wire is the 'neutral' wire.

The ribbed wire is the 'hot' wire.