AC power plugs and socket-outlets

AC power plugs and socket-outlets are devices that allow electrically operated devices to be connected to the primary alternating current (AC) power supply in a building. Electrical plugs and socket-outlets differ in voltage and current rating, shape, size and type of connectors. The types used in each country are set by national standards, but the national standards bodies also submit standardized description sheets to the IEC which collates them as IEC 60083 “Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC”.

Generally the plug is the movable connector attached to an electrically operated device's mains cable, and the socket-outlet is fixed on equipment or a building structure. Plugs have male circuit contacts, while socket-outlets have female contacts. The plug has protruding prongs, blades, or pins that fit into matching slots or holes in the socket-outlet. A socket-outlet is also called a receptacle or outlet, or power point, plug socket, wall socket, wall plug, and 13 amp sockets.

To reduce the risk of electric shock, plug and socket-outlet systems can incorporate safety features. These may include socket design intended to accept only compatible plugs inserted in the correct orientation; recessed sockets; plugs with insulated sleeves; or socket-outlets with blocking shutters. Socket-outlets are designed to prevent exposure of bare live contacts. The exposed contacts present in some socket-outlets are used exclusively for grounding.

Socket-outlets that take a variety of plug types can be found in where market size or local market conditions make a specific plug standard impractical to implement. Socket-outlets may accept plugs to various European, Asian, North American, British or Australian standards. Multi-standard socket-outlets do not safeguard against devices being damaged by the wrong voltage. Users must know the voltage requirements of their appliances as well as the prevailing local voltage. Some devices are compatible with a wide range of voltages and frequencies.

These socket-outlets have one or more ground holes to allow 3-pin plugs. On properly wired circuits, the ground contact will be connected to earth ground. They may not provide grounding to all types of plugs, as is the case of French plugs where the grounding pin that mates with the plug is part of the socket-outlet rather than the plug.

Plug and socket-outlet systems intended for high current, high voltage or polyphase industrial equipment, as well as additional contacts and larger contacts, may also include features to improve the security and safety of use. For example, a high-power plug may include a locking ring or twist-lock feature to prevent accidental disconnection in use. A socket-outlet may include a mechanical interlock that prevents insertion or removal of a plug unless the local safety disconnecting switch is open. Plugs may include special measures to contain an arc generated during disconnection. Plugs used for equipment in wet locations may include small supervisory contacts that check the integrity of the grounding conductor.