An electrical power plug or receptacle with an over-temperature protection function, including a reset switch operated by a solenoid that electrically connects and disconnects the input side and output side electrical lines, and an temperature-controlled switch disposed in thermal contact with one or more electrical conductor plates on the input or output side. The temperature-controlled switch is connected in series with the solenoid between the output side phase and neutral lines. When the temperature of the temperature-controlled switch is within a normal range, the switch is open and does not form a current path with the solenoid. When the temperature is at or above a threshold temperature, the temperature-controlled switch is closed, a current flows through the switch and the solenoid between the output side phase and neutral lines, and the solenoid operates the reset switch to disconnect the input side from the output side.