A plug comprises power contacts and a trip jumper having jumper contacts configured to make a trip connection, during a plugging action with the plug and a receptacle, with mating trip contacts in the receptacle. When the receptacle is connected to electrical power during the plugging action, a current over the trip connection can cause disconnection of a receptacle power contact from the power. A receptacle comprises receptacle power contacts and a trip circuit having receptacle trip contacts configured to make a trip connection, during a plugging action with the receptacle and plug, with mating trip contacts in the plug. When the receptacle is connected to electrical power during the plugging action, a current over the trip connection can cause disconnection of power to a receptacle power contact. A system can have an electrical device with a line cord connected to the plug.