An AC line power coupling system secures a conventional plug (700) of an appliance cord or extension cord (702). A adapter (400) is fitted onto the prongs (704) of the cord, and semi-permanently attached with a connector (300) including two half housings (301 and 302) that fasten over the plug and a clamp (200) that holds the cord. The adapter prongs mate, which have a conventional layout, with a special socket (600). The adapter is locked onto the socket by a sleeve (500). The sleeve moves relative to the socket, rotating and axially sliding. When the sleeve is slid onto the protruding cylindrical end of the adapter and rotated, lugs on the inside of the sleeve engage in grooves, locking the adapter to the socket; the sleeve motion is reversed to unlock. The adapter can be plugged into conventional sockets while the connector remains fastened over the plug, but when plugged into the special socket and locked, the cord is prevented from pulling out under tension. The special socket can be adapted to junction boxes as well as to power cords.