AC power plugs and sockets

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AC power plugs and sockets allow electric equipment to be connected to the alternating current (AC) power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and current rating, shape, size, and connector type. Different standard systems of plugs and sockets are used around the world.

Alternating current electric voltage which periodically reverses direction; form in which electric power is delivered to businesses and residences; form of electrical energy that consumers typically use when they plug electric appliances into a wall socket

Alternating current (AC) is an electric current which periodically reverses direction, in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans and electric lamps into a wall socket. A common source of DC power is a battery cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.

Mains electricity general-purpose alternating-current electric power supply delivered to homes and businesses, used by consumer for domestic appliances, televisions and electric lamps through wall outlets

Mains electricity is the general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to homes and businesses, and it is the form of electrical power that consumers use when they plug domestic appliances, televisions and electric lamps into wall outlets.

Voltage difference in the electric potential between two points in space

Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points. The difference in electric potential between two points in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule per 1 coulomb. The official SI definition for volt uses power and current, where 1 volt = 1 watt per 1 ampere. This definition is equivalent to the more commonly used 'joules per coulomb'. Voltage or electric potential difference is denoted symbolically by V, but more often simply as V, for instance in the context of Ohm's or Kirchhoff's circuit laws.

Contents

Plugs and sockets for portable appliances became available in the 1880s, to replace connections to light sockets with wall-mounted outlets. A proliferation of types developed for both convenience and protection from electrical injury. Today there are about 20 types in common use around the world, and many obsolete socket types are found in older buildings. Coordination of technical standards has allowed some types of plug to be used across large regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods.

Electrical injury physiological reaction or injury caused by electric current (see Q3587621 for death by electrocution)

Electrical injury is a physiological reaction caused by electric current passing through the (human) body. Electric shock occurs upon contact of a (human) body part with any source of electricity that causes a sufficient magnitude of current to pass through the victim's flesh, viscera or hair. Physical contact with energized wiring or devices is the most common cause of an electric shock. In cases of exposure to high voltages, such as on a power transmission tower, physical contact with energized wiring or objects may not be necessary to cause electric shock, as the voltage may be sufficient to "jump" the air gap between the electrical device and the victim.

Some multi-standard sockets allow use of several types of plug; improvised or unapproved adaptors between incompatible sockets and plugs may not provide the full safety and performance of an approved socket–plug combination.

Concepts and terminology

Schuko plug and socket.png
French-power-socket.jpg
Plugs and sockets may sometimes combine male and female contacts. Clockwise from top left: CEE 7/4 (German) plug; a matching CEE 7/3 socket with exposed earth (ground) projections on circumference of socket; CEE 7/5 (French) socket with projecting earth pin. Typically no energy is supplied to any exposed pins or terminals on the socket, for safety.

A plug is the movable connector attached to an electrically operated device, and the socket is fixed on equipment or a building structure and connected to an energised electrical circuit. The plug is a male connector with protruding pins that match the openings and female contacts in a socket. Some plugs have female contacts that are used only for an earth ground connection. Some plugs have built-in fuses for safety.

Gender of connectors and fasteners designation differentiating two dissimilar connectors which together form a physical connexion -- Used to describe connexions for spacecraft docking, electronics, plumbing, etc.

In electrical and mechanical trades and manufacturing, each half of a pair of mating connectors or fasteners is conventionally assigned the designation male or female. The "female" connector is generally a receptacle that receives and holds the "male" connector. On occasion, the terms "male" and "female" are respectively referred to as the A and B ends, though the names of some standards conflict with this as they contain the letters A or B within the name; unambiguous, though rare, terms include plug and socket or jack.

Ground (electricity) reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth

In electrical engineering, ground or earth is the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the earth.

Fuse (electrical) type of low resistance resistor that acts as a sacrificial device to provide overcurrent protection, of either the load or source circuit

In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby interrupting the current. It is a sacrificial device; once a fuse has operated it is an open circuit, and it must be replaced or rewired, depending on type.

To reduce the risk of electric shock, plug and socket systems have safety features in addition to the recessed contacts of the energised socket. These may include plugs with insulated sleeves, recessed sockets, or automatic shutters to block socket apertures when a plug is removed.

Insulator (electricity) material whose internal electric charges do not flow freely, and which therefore does not conduct an electric current

An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors.

A socket may be surrounded by a decorative or protective cover [1] which may be integral with the socket.

Single-phase sockets have two current-carrying connections to the power supply circuit, and may also have a third pin for a safety connection to earth ground. Depending on the supply system, one or both current-carrying connections may have significant voltage to earth ground.

Single-phase electric power

In electrical engineering, single-phase electric power is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting, and such motors are uncommon above 10 kW in rating.

    History

    When commercial electric power was first introduced in the 1880s, it was used primarily for lighting. Other portable appliances (such as vacuum cleaners, electric fans, smoothing irons, and curling-tong heaters) were connected to light-bulb sockets.

    As early as 1885 a two-pin plug and wall socket format was available on the British market. By about 1910 the first three-pin earthed (grounded) plugs appeared. Over time other safety improvements were gradually introduced to the market. The earliest national standard for plug and wall socket forms was set in 1915. [ citation needed ]

    Application issues

    Types of power plugs and sockets used by country. Map of the world coloured by type of mains plug used.svg
    Types of power plugs and sockets used by country.

    Designs of plugs and sockets have gradually developed to reduce the risk of electric shock and fire. Safety measures include; pin and aperture dimensions, a plug topology that permits only proper insertion of a plug into a socket, and earth (ground) pins that make contact before line (power) pins can be connected. Some types can also include fuses and switches.

    Shutters

    Shutters on the socket prevents foreign objects from contacting live contacts. The first shuttered socket was introduced by British manufacturer Crompton, in 1893. Electrical insulation of the pin shanks to reduce live contact exposure was added to some designs, as early as 1905. [2]

    Earthing (grounding)

    A third contact for a connection to earth is intended to protect against insulation failure of the connected device. Some early unearthed plug and socket types were revised to include an earthing pin or phased out in favour of earthed types.

    Different types of plug are used for different IEC appliance classes. The assigned class depends on whether the device is earthed and the degree of insulation it incorporates. Class I, for example, refers to earthed equipment that requires a third contact in the plug and socket, while Class II refers to unearthed equipment protected by double insulation.

    Polarization

    Polarization is maintained by the design of the plug, socket and contacts so that a plug fits only one way into a socket. Where the building wiring system defines a "neutral" conductor that is close to earth potential, it is safer for people interacting with the equipment to preserve that distinction. For example, appliances may ensure that single-pole switches interrupt the line side of the circuit, or ensure that screw-base lampholder shells are connected to the neutral side of the supply, minimizing the chance of contact with live parts. In most designs, "polarized" plugs cannot be mated with non-polarized sockets. Wiring systems where both circuit conductors have a significant potential with respect to earth do not benefit from polarized plugs.

    Universal sockets

    "Universal" or "multi-standard" sockets are intended to accommodate plugs of various types. In some jurisdictions, they violate safety standards for sockets. [3] [4]

    Safety advocates, the United States Army, [5] and a manufacturer of sockets [6] point out a number of safety issues with universal socket and adapters, including voltage mismatch, exposure of live pins, lack of proper earth ground connection, or lack of protection from overload or short circuit. Universal sockets may not meet technical standards for durability, plug retention force, temperature rise of components, or other performance requirements, as they are outside the scope of national and international technical standards.

    A technical standard may include compatibility of a socket with more than one form of plug. The Thai dual socket is specified in figure 4 of TIS 166-2549 (shown below) and is designed to accept Thai plugs, and also Type A, B and C plugs. Chinese dual sockets have both an unearthed socket complying with figure 5 of GB 1002-2008 (both flat pin and 4.8 mm round pin), and an earthed socket complying with figure 4 of GB 1002-2008. The exception is that both Thai and Chinese dual sockets also accept 120 V rated plugs, potentially causing an electrical incompatibility because both states use a 220 V residential voltage.

    Voltage rating of plugs and power cords

    NEMA 5-15 (type B) plugs with current and voltage ratings shown (left) on label (7 A 125 V) and (centre) on engagement face (10 A 125 V). Also shown (right) is the rating on the C13 connector at the other end of the 10 A 125 V appliance cord. NEMA Plug Ratings.jpg
    NEMA 5-15 (type B) plugs with current and voltage ratings shown (left) on label (7 A 125 V) and (centre) on engagement face (10 A 125 V). Also shown (right) is the rating on the C13 connector at the other end of the 10 A 125 V appliance cord.

    Plugs and power cords have a rated voltage and current assigned to them by the manufacturer, and these values are marked on the plug. Using an appliance, plug, or power cord that is inappropriate for the load may be a safety hazard. For example, high-current equipment can cause a fire when plugged into an extension cord with a current rating lower than necessary. Sometimes the cords used to plug in dual voltage 120 V / 240 V equipment are rated only for 125 V, so care must be taken by travellers to use only cords with an appropriate voltage rating.

    Appliance connections and extensions

    So that manufacturers need not build many similar appliances differing only in the type of plug fitted, a common strategy is to provide an IEC 60320 inlet on the appliance and a detachable power cord (mains flex lead) and appropriate plug. The appliance need only to be tested to the power inlet. Some appliances have a switch for selection of voltage.

    A Plug Strip with 2 USB ports and built in Surge Protection Tricklestar Plug Strip.jpg
    A Plug Strip with 2 USB ports and built in Surge Protection

    Extension cords (extension leads) are used for temporary connections when a socket is not within convenient reach of an appliance's power lead. A power strip with multiple sockets may also have a switch, surge voltage protection, or over-current protection.

    Special purpose plugs and sockets

    Special purpose sockets may be found in residential, industrial, commercial or institutional buildings. Examples of systems using special purpose sockets include:

    Special-purpose sockets may be labelled or coloured to identify a reserved use of a system, or may have keys or specially shaped pins to prevent use of unintended equipment.

    Shaver supply units

    Shaver supply unit for BS 4573, US Type A, Australian two-pin, and Europlug Type C. ShaverSocketUK.jpg
    Shaver supply unit for BS 4573, US Type A, Australian two-pin, and Europlug Type C.

    National wiring regulations sometimes prohibit the use of sockets within certain areas adjacent to water taps, etc. A special socket, with an isolation transformer, may allow electric razors to be used near a sink. Because the isolation transformer is of low rating, such outlets are not suitable to operate higher-powered appliances such as blow dryers.

    An IEC standard 61558-2-5, adopted as CENELEC standard EN 61558-2-5 and also as a national standard in some countries, describes one type of shaver supply unit. Shaver sockets may accept multiple two-pin plug types including Europlug (Type C), Australian (Type I) and BS 4573. The isolation transformer often includes a 115 V output accepting two-pin US plugs (Type A). Shaver supply units must also be current limited, IEC 61558-2-5 specifies a minimum rating of 20  VA and maximum of 50 VA. [10] IEC 61558-2-5 requires sockets to be marked with the shaver symbol defined in IEC 60417-5225, the words "shavers only" are also often used but not required.

    Isolation transformers and special shaver receptacles were once standard installation practice in North America, but now a GFCI receptacle is used instead. This provides the full capacity of a standard receptacle but protects the user of a razor or other appliance from leakage current.

    Types in present use

    The plugs and sockets used in a given area are regulated by local governments.

    The International Electrotechnical Commission (IEC) maintains a guide with letter designations for generally compatible types of plugs, [11] which expands on earlier guides published by the United States Department of Commerce. This is a de facto naming standard and guide to travellers. Some letter types correspond to several current ratings or different technical standards, so the letter does not uniquely identify a plug and socket within the type family, nor guarantee compatibility. Physical compatibility of the plug and socket does not ensure correct voltage, frequency, or current capacity. Not all plug and socket families have letters in the IEC guide, but those that have are noted in this article, as are some additional letters commonly used by retail vendors. [12]

    In Europe, CENELEC publishes a list of approved plug and socket technical standards used in the member countries. [13]

    Argentina IRAM 2073 and 2071 (Type I)

    Argentinian 1996 power plug arrangement IRAM 2073 arragment.png
    Argentinian 1996 power plug arrangement

    The plug and socket system used in Class 1 applications in Argentina is defined by IRAM standards. These two standards are; IRAM 2073 "Two pole plugs with earthing contact for domestic and similar purposes, rated 10 A and 20 A, 250 V AC" and IRAM 2071 "Two pole socket – outlets with earthing contact for 10 A and 20 A, 250 V AC., for fixed installations." The plug and socket system is similar in appearance to the Australian and Chinese plugs. It has an earthing pin and two flat current-carrying pins forming an inverted V-shape (120°). The flat pins for the 10 A version measure 6.25 by 1.55 mm (0.246 by 0.061 in) and 8.0 by 1.9 mm (0.315 by 0.075 in) for the 20 A version, and are set at 30° to the vertical at a nominal pitch of 7.92 mm (0.312 in). The pin length is the same as in the Chinese version. The earthing pin length is 21.4 mm (0.843 in) for the 10 A version and 21.8 mm (0.858 in) for the 20 A version. On the plugs, the pole length is 18.2 mm (0.717 in) for the 10 A version and 17.8 mm (0.701 in) for the 20 A version. The most important difference from the Australian plug is that the Argentinian plug is wired with the line and neutral contacts reversed.

    In Brazil, similar plugs and sockets are still commonly used for high-power appliances like air conditioners, dishwashers, and household ovens. Although being often called "Argentinian plug," it is actually based on the American NEMA 10-20 standard, and is incompatible with Argentinian IRAM plugs. Since Brazil adopted the NBR 14136 standard which includes a 20 A version, the original motivation to use the NEMA 10-20 plug has ceased to exist.[ citation needed ]

    Australian/New Zealand standard AS/NZS 3112 (Type I), used in Australasia

    Australian 2005 standard power plug with insulated pins Aust AC plug.jpg
    Australian 2005 standard power plug with insulated pins
    Australasian switched 3-pin dual power point (socket) rated 10 amperes Australian dual switched power point.jpg
    Australasian switched 3-pin dual power point (socket) rated 10 amperes

    This Australian/New Zealand standard is used in Australia, New Zealand, Fiji, Tonga, Solomon Islands, and Papua New Guinea. It defines a plug with an earthing pin and two flat current-carrying pins forming an inverted V-shape. [14] The flat pins measure 6.5 by 1.6 mm (0.256 by 0.063 in) and are set at 30° to the vertical at a nominal pitch of 13.7 mm (0.539 in). Australian and New Zealand wall sockets almost always have switches on them for extra safety, as in the UK. An unearthed version of this plug with two angled power pins but no earthing pin is used with small double-insulated appliances, but the sockets always include an earth contact.

    There are several AS/NZS 3112 plug variants, including ones with larger or differently shaped pins used for devices drawing 15, 20, 25 and 32 A. These sockets accept plugs of equal or of a lower current capacity, but not of higher capacity. For example, a 10 A plug will fit all sockets but a 20 A plug will fit only 20, 25 and 32 A sockets. In New Zealand PDL 940 "Tap-on" or Piggy-back plugs are available which allow a second 10 A plug, or a charger, to be fitted to the rear of the plug.

    Australia's standard plug/socket system was originally codified as standard C112 (floated provisionally in 1937, and adopted as a formal standard in 1938), which was superseded by AS 3112 in 1990. The requirement for insulated pins was introduced in the 2004 revision. [15] The current version is AS/NZS 3112:2011, Approval and test specification – Plugs and socket-outlets.

    Brazilian standard NBR 14136 (Type N)

    Brazil, which had been using mostly Europlugs, and NEMA 1–15 and NEMA 5–15 standards, adopted a (non-compliant) variant of IEC 60906-1 as the national standard in 1998 under specification NBR 14136 (revised in 2002). [16] These are used for both 220-volt and 127-volt regions of the country, despite the IEC 60906-2 recommendation that NEMA 5-15 be used for 120 V connections. There are two types of sockets and plugs in NBR 14136: one for 10 A, with a 4.0 mm pin diameter, and another for 20 A, with a 4.8 mm pin diameter. [17] This differs from IEC 60906-1 which specifies a pin diameter of 4.5 mm and a rating of 16 A. NBR 14136 does not require shutters on the apertures, a further aspect of non-compliance with IEC 60906-1. NBR 14136 was not enforced in that country until 2007, when its adoption was made optional for manufacturers. It became compulsory on 1 January 2010.

    Few private houses in Brazil have an earthed supply, so even if a three-pin socket is present it is not safe to assume that all three terminals are actually connected. Most large domestic appliances were sold with the option to fit a flying earth tail to be locally earthed, but many consumers were unsure how to use this and so didn't connect it. The new standard has an earth pin, which in theory eliminates the need for the flying earth tail. [18]

    British and compatible standards

    BS 546 plugs. Left to right: 15 A, 5 A and 2 A. BS 546 Plugs - 15A 5A 2A.png
    BS 546 plugs. Left to right: 15 A, 5 A and 2 A.

    BS 546, "Two-pole and earthing-pin plugs, socket-outlets and socket-outlet adaptors for AC (50-60 Hz) circuits up to 250V" describes four sizes of plug rated at 2 A, 5 A (Type D), 15 A (Type M) and 30 A. The plugs have three round pins arranged in a triangle, with the larger top pin being the earthing pin. The plugs are polarized and unfused. Plugs are non-interchangeable between current ratings. Introduced in 1934, the BS 546 type has mostly been displaced in the UK by plugs and sockets to the BS 1363 standard. According to the IEC [19] some 40 countries use Type D and 15 countries use Type M. Some, such as India and South Africa, use standards based on BS 546.

    BS 1363 (Type G)

    BS 1363 rewirable plug BritishPlugforWikipedia.jpg
    BS 1363 rewirable plug
    Comparison of moulded plugs. Schuko type weighing 47g and BS 1363 weighing 44g, both manufactured by Longwell Company Schuko & BS 1363 Longwell Plugs.jpg
    Comparison of moulded plugs. Schuko type weighing 47g and BS 1363 weighing 44g, both manufactured by Longwell Company

    BS 1363 "13 A plugs, socket-outlets, adaptors and connection units" [20] is the main plug and socket type used in the United Kingdom. According to the IEC [11] it is also used in over 50 countries worldwide. Some of these countries have national standards based on BS 1363, including: Ireland, Malaysia, Malta, Singapore, and Saudi Arabia.

    This plug, commonly called a 13 A plug or 13 amp plug, has three rectangular pins forming an isosceles triangle. The BS 1363 plug has a fuse which is suitably rated to protect the appliance and its flexible cord from overload and consequent fire risk. Modern appliances may only be sold with a fuse of the appropriate size preinstalled.

    BS 4573 (UK shaver)

    BS 4573 Plug ShaverPlugUK.jpg
    BS 4573 Plug

    In the United Kingdom, Ireland, and Malta, there is a two-pin plug and socket for use with electric shavers and toothbrushes, defined by the BS 4573 standard. [21] The plug has insulated sleeves on the pins. Although superficially similar to the Europlug Type C, the diameter and spacing of the pins are slightly different.

    CEE 7 standards

    The International Commission on the Rules for the Approval of Electrical Equipment (IECEE) was a standards body which published Specification for plugs and socket-outlets for domestic and similar purposes as CEE Publication 7, known simply as CEE 7. It was originally published in 1951, the 2nd edition was published in May 1963 and was last updated by Modification 4 in March 1983. [22] CEE 7 consists of general specifications, plus a number of standard sheets for specific connectors.

    A number of standards based on two round pins with centres spaced at 19 mm are in use in continental Europe and elsewhere, most of which are listed in IEC/TR 60083 "Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC". [23] There is no European Union regulation of domestic mains plugs and sockets, and the Low Voltage Directive specifically excludes domestic plugs and sockets. [24] EU countries each have their own regulations and national standards; for example, some require child-resistant shutters, while others do not. CE marking is neither applicable nor permitted on plugs and sockets.

    CEE 7/1 unearthed socket and CEE 7/2 unearthed plug

    CEE 7/1 unearthed sockets are designed to accept CEE 7/2 round plugs without notches in the body and having 4.8 by 19 mm (0.189 by 0.748 in) pins.

    Because they have no earth connections they have been or are being phased out in most countries. The regulations of countries using the CEE 7/3 and CEE 7/5 socket standards vary in whether CEE 7/1 sockets are still permitted in environments where the need for earthing is less critical. Sweden, for example, prohibited them from new installations in 1994. In Germany unearthed sockets are rare, whereas in the Netherlands and Sweden it is still common to find them in "dry areas" such as in bedrooms or living rooms. Some countries prohibit use of unearthed and earthed sockets in the same room, in the "insulated room" concept, so that people cannot touch an earthed object and one that has become live, at the same time.

    The depth of the sockets varies between countries and age. Older sockets are so shallow that it is possible to touch the pins of a plug when the plug is inserted only deep enough to get electrical power on the pins, while newer sockets are deep enough to protect from this kind of accident. CEE 7/1 sockets accept CEE 7/4, CEE 7/6 and CEE 7/7 plugs without providing an earth connection. The earthed CEE 7/3 and CEE 7/5 sockets were specifically designed not to allow insertion of CEE 7/2 unearthed round plugs fitted to older appliances which had to be earthed via other means.

    Two Schuko (CEE 7-3) socket-outlets manufactured by Busch-Jaeger Elektro GmbH, the lower has (black) protective shutters, the upper does not, revealing internal metal contacts. Schuko (CEE 7-3) socket-outlets, with and without shutters.jpg
    Two Schuko (CEE 7-3) socket-outlets manufactured by Busch-Jaeger Elektro GmbH, the lower has (black) protective shutters, the upper does not, revealing internal metal contacts.

    CEE 7/3 socket and CEE 7/4 plug (German "Schuko"; Type F)

    Schuko plug (CEE 7/4) and socket (CEE 7/3) Schuko plug and socket.png
    Schuko plug (CEE 7/4) and socket (CEE 7/3)

    The CEE 7/3 socket and CEE 7/4 plug are commonly called Schuko . The socket (which is often, in error, also referred to as CEE 7/4) has a predominantly circular recess which is 17.5 mm (0.689 in) deep with two symmetrical round apertures and two earthing clips on the sides of the socket positioned to ensure that the earth is always engaged before live pin contact is made. The plug pins are 4.8 by 19 mm (0.189 by 0.748 in). The Schuko connection system is symmetrical and unpolarised in its design, allowing line and neutral to be reversed. The socket also accepts Europlugs and CEE 7/17 plugs. It is rated at 16 A. The current German standards are DIN 49441:1972-06 "Two-pole plugs with earthing-contact 10 A 250 V≅ and 10 A 250 V–, 16 A 250 V∼" (which also includes CEE 7/7 plug) and DIN 49440-1:2006-01 "Two-pole socket-outlets with earthing contact, 16 A 250 V a.c."

    In addition to Germany, it is used in Albania, Austria, Belarus, Bosnia and Herzegovina, Bulgaria, Chile, Croatia, Denmark, Estonia, Finland, Georgia, Greece, Hungary, Iceland, Indonesia, Iran, Italy (standard CEI 23-50), Kazakhstan, Latvia, Lithuania, Luxembourg, Republic of Macedonia, Republic of Moldova, the Netherlands, Norway, Pakistan, Peru [25] , Portugal, Romania, Russia, [26] Serbia, Slovenia, South Korea [27] , Spain, Sweden, Turkey, Ukraine, and Uruguay.

    It was widely used in Ireland until 1964, a legacy of Ireland's early electricity grid which was largely built based on design work on the Shannon hydroelectric scheme by Siemens-Schuckert. The British BS1363 (localised as Irish Standard I.S.401) was adopted as the new standard plug to ease import of electrical appliances from the UK. CEE 7/1 and CEE 7/4 are still occasionally found in less used areas of some older homes, particularly in outbuildings or hot presses.

    Schuko is an abbreviation for the German word Schutzkontakt, which means "Protective contact" - in this case "protective" refers to the earth.

    Some countries, including South Korea, Portugal, Finland, Denmark, [28] Norway and Sweden, require child-proof socket shutters; the German DIN 49440-1:2006-01 standard does not have this requirement.

    CEE 7/5 socket and CEE 7/6 plug (French; Type E)

    French socket French-power-socket.jpg
    French socket
    Rewireable French plug French Plug CEE 7 6.jpg
    Rewireable French plug

    The CEE 7/5 socket and CEE 7/6 plug are defined in French standard NF C 61-314 "Plugs and socket-outlets for household and similar purposes" (which also includes CEE 7/7, 7/16 and 7/17 plugs) The socket has a predominantly circular recess which is 15 mm (0.591 in) deep with two symmetrical round apertures and a round 4.8 mm (0.189 in) earth pin projecting from the socket such that the tip is 23 mm (0.906 in) beyond the live contacts, to ensure that the earth is always engaged before live pin contact is made. The earth pin is centred between the apertures, offset by 10 mm (0.394 in). The plug (which is often, in error, also referred to as CEE 7/5) has two round pins measuring 4.8 by 19 mm (0.189 by 0.748 in), spaced 19 mm (0.748 in) apart and with an aperture for the socket's projecting earth pin. This standard is also used in Belgium, Denmark, Poland, the Czech Republic, Slovakia and some other countries.

    Although the plug is polarised, CEE 7 does not define the placement of the line and neutral and there is no universally-observed standard. However, the Czech standard recommends that the line wire be on the left side when facing the socket. The French convention changed circa 2002 from nothing particular, to, if the earth pin was at the top then the line hole in the socket would be on the right looking at the socket.[ citation needed ] However, the socket may not necessarily be installed with the earth pin at the top. Packaging in France of sockets is normally marked with correct connection of the cables. Polarised pre-fitted plugs on appliances are therefore connected with the brown line wire to the right pin and the blue neutral wire to the left, the earth being connected to the contact at the "top" of the plug.

    CEE 7/2 and 7/4 plugs are not compatible with the CEE 7/5 socket because of the round earthing pin permanently mounted in the socket.

    CEE 7/7 plug (compatible with E and F)

    CEE 7/7 plug CEE 7-7.jpg
    CEE 7/7 plug

    To bridge the differences between German and French standards, the CEE 7/7 plug was developed. It is polarised to prevent the line and neutral connections from being reversed when used with a French CEE 7/5 socket, but allows polarity reversal when inserted into a German CEE 7/3 socket. The plug is rated at 16 A.

    It has earthing clips on both sides to connect with the CEE 7/3 socket and a female contact to accept the earthing pin of the CEE 7/5 socket. Currently, appliances in many countries are sold with non-rewireable CEE 7/7 plugs attached, enabling use in all countries whose socket standards are based on either CEE 7/3 or CEE 7/5.

    This plug can be inserted into a Danish Type K socket, but earthing is not enabled.

    CEE 7/16 plugs

    The CEE 7/16 standard sheet appears in Supplement 2 (June 1962) to the 1951 edition of CEE 7. The CEE 7/16 unearthed plug is used for low power Class II applications, it has two round 4 by 19 mm (0.157 by 0.748 in) pins, rated at 2.5 A. There are two variants.

    CEE 7/16 Alternative I

    Alternative I is a round plug with cutouts to make it compatible with CEE 7/3 and CEE 7/5 sockets. (The similar-appearing CEE 7/17 has larger pins and a higher current rating.) This alternative is seldom used.

    CEE 7/16 Alternative II "Europlug" (Type C)
    Example of a Europlug Euro-Flachstecker 2.jpg
    Example of a Europlug

    Alternative II, popularly known as the Europlug, is a flat plug defined by Cenelec standard EN 50075 and national equivalents. The Europlug is not rewirable and must be supplied with a flexible cord. It can be inserted in either direction, so line and neutral are connected arbitrarily.

    There is no socket defined by EN 50075; neither is there a socket specified in CEE 7 to accept only the Europlug. Instead, the Europlug was designed to be compatible with a range of sockets in common use in Europe. These sockets, including the CEE 7/1, CEE 7/3 (German/"Schuko"), CEE 7/5 (French), and most Israeli, Swiss, Danish and Italian sockets, were designed to accept pins of various diameters, mainly 4.8 mm but also 4.0 mm and 4.5 mm, and are usually fed by final circuits with either 10 A or 16 A overcurrent protection devices. [29] To improve contact with socket parts the Europlug has slightly flexible pins which converge toward their free ends.

    UK shaver sockets designed to accept BS 4573 shaver plugs also accept Europlugs for applications requiring less than 200 mA. [30] Other than such personal hygiene applications, UK consumer protection legislation [31] does not permit Europlugs.

    The Europlug is also used in the Middle East, Africa, South America, and Asia .

    CEE 7/17 unearthed plug

    CEE 7/17 plug CEE 7-17 plug.jpg
    CEE 7/17 plug

    This is a round plug which conforms to a shape compatible with CEE 7/1, CEE 7/3, and CEE 7/5 sockets. It has two round pins measuring 4.8 by 19 mm (0.189 by 0.748 in). It may be rated at either 10 A or 16 A, and may be used for unearthed Class II appliances (and in South Korea for all domestic non-earthed appliances). It is also defined as the Class II plug in Italian standard CEI 23-50. It can be inserted into Israeli SI 32 with some difficulty. The Soviet GOST 7396 standard includes both the CEE 7/17 and the CEE 7/16 variant II plug.

    Danish Section 107-2-D1 earthed (Type K)

    Danish 107-2-D1, standard DK 2-1a, with round power pins and half round earth pin 107-2-D1 - Danish electrical plugs - Studio 2011.jpg
    Danish 107-2-D1, standard DK 2-1a, with round power pins and half round earth pin
    Danish unearthed and switched socket Gniazdo el z przelacznikiem (ubt).JPG
    Danish unearthed and switched socket
    Socket for the tilted flattened pins and half-round earth pin of Danish computer equipment plug (mainly used in professional environment), standard DK 2-5a DanishComputerPlugSocket-DK-2-5a.png
    Socket for the tilted flattened pins and half-round earth pin of Danish computer equipment plug (mainly used in professional environment), standard DK 2-5a

    This Danish standard plug is described in the Danish Plug Equipment Section 107-2-D1 Standard sheet (SRAF1962/DB 16/87 DN10A-R). The Danish standard provides for sockets to have child-resistant shutters.

    The Danish socket will also accept the CEE 7/16 Europlug or CEE 7/17 Schuko-French hybrid plug. CEE 7/4 (Schuko), CEE 7/7 (Schuko-French hybrid), and earthed CEE 7/6 French plugs will also fit into the socket but will not provide an earth connection and may be attached to appliances requiring more than the 13 A maximum rating of the socket.

    A variation (standard DK 2-5a) of the Danish plug is for use only on surge protected computer sockets. It fits into the corresponding computer socket and the normal socket, but normal plugs deliberately don't fit into the special computer socket. The plug is often used in companies, but rarely in private homes.

    There is a variation for hospital equipment with a rectangular left pin, which is used for life support equipment.

    Traditionally all Danish sockets were equipped with a switch to prevent touching live pins when connecting/disconnecting the plug. Today, sockets without switch are allowed, but then it is a requirement that the sockets have a cavity to prevent touching the live pins. The shape of the plugs generally makes it difficult to touch the pins when connecting/disconnecting.

    Since the early 1990s earthed sockets have been required in all new electric installations in Denmark. Older sockets need not be earthed, but all sockets, including old installations, must be protected by earth-fault interrupters (HFI or HPFI in Danish) by 1 July 2008.

    As of 1 July 2008, wall sockets for French 2-pin, female earth CEE 7/5 are permitted for installations in Denmark. [32] This was done because no electrical equipment sold to private users is equipped with a Danish plug.

    CEE 7/3 sockets were not permitted until 15 November 2011 [33] . Many international travel adaptor sets sold outside Denmark match CEE 7/16 (Europlug) and CEE 7/7 (Schuko-French hybrid) plugs which can readily be used in Denmark.

    Italy (Type L)

    Ita plug 16A 10A.jpg
    Italian sockets.jpg
    Side by side comparison of Italian CEI 23-50 S 11 and S 17 plugs and sockets rated 16 A (left) and 10 A (right).

    Italian plugs and sockets are defined by the standard CEI 23-50 which superseded CEI 23-16. This includes models rated at 10 A and 16 A that differ in contact diameter and spacing (see below for details) [34] . Both are symmetrical, allowing the line and neutral contacts to be inserted in either direction. This plug is also commonly used in Chile and Uruguay.

    10 A plugs and socket
    Pins which are 4 mm in diameter, the centres spaced 19 mm apart. The 10 A three-pin earthed rear entry plug is designated CEI 23-50 S 11 (there are also two side-entry versions, SPA 11 and SPB 11). The 10 A two-pin unearthed plug is designated CEI 23-50 S 10. The 10 A three-pin earthed socket is designated CEI 23-50 P 11, and the 10 A two-pin unearthed socket is designated CEI 23-50 P 10. Both 10 A sockets also accept CEE 7/16 (Europlugs).
    16 A plug and socket
    Pins which are 5 mm in diameter, the centres spaced 26 mm apart. The 16 A three-pin earthed rear entry plug is designated CEI 23-50 S 17 (there are also two side-entry versions, SPA 17 and SPB 17). The 16 A two-pin unearthed plug is designated CEI 23-50 S 16. The 16 A three-pin earthed socket is designated CEI 23-50 P 17, there is not a 16 A two-pin unearthed socket. The 16 A socket used to be referred to as per la forza motrice [35] (for electromotive force, see above) or sometimes (inappropriately) industriale (industrial) or even calore.
    Old adaptor from forza to 2 x luce and 1 x forza ForzaLuce1950.jpg
    Old adaptor from forza to 2 × luce and 1 × forza

    The two standards were initially adopted because up to the second half of the 20th century in many regions of Italy electricity was supplied by means of two separate consumer connections – one for powering illumination and one for other purposes – and these generally operated at different voltages, typically 127 V single phase and 220 V single phase (from 3-phase 380 V) or two phase (from 220 V 3-phase). The electricity on the two supplies was separately metered, was sold at different tariffs, was taxed differently and was supplied through separate and different sockets. [36] Even though the two electric lines (and respective tariffs) were gradually unified beginning in the 1960s (the official, but purely theoretical date was the summer of 1974) [37] many houses had dual wiring and two electricity meters for years thereafter; in some zones of Lazio the 127 V network was provided for lighting until 1999. The two gauges for plugs and sockets thus became a de facto standard which is now formalized under CEI 23-50. Some older installations have sockets that are limited to either the 10 A or the 16 A style plug, requiring the use of an adaptor if the other gauge needs to be connected. Numerous cross adaptors were used.

    Almost every appliance sold in Italy nowadays is equipped with CEE 7/7 (German/French), CEE 7/16 or CEE 7/17 plugs, but the standard Italian sockets will not accept the first and the third ones since the pins of the CEE 7/7 and CEE 7/17 plugs are thicker (4.8 mm) than the Italian ones (4 mm); besides the pins are not sheathed and forcing them into a linear Italian socket may lead to electric shock. Adaptors are standardized in Italy under CEI 23-57 which can be used to connect CEE 7/7 and CEE 7/17 and plugs to linear CEI 23-50 sockets.

    Europlugs are also in common use in Italy; they are standardized under CEI 23-34 S 1 for use with the 10 A socket and can be found fitted to Class II appliances with low current requirement (less than 2.5 A).

    The current Italian standards provide for sockets to have child-resistant shutters ("Sicury" patent). [38]

    Italian multiple standard sockets

    Adapted schuko.jpg
    CEI 23-50 17/11 (Bipasso) socket (#1) and CEI 23-50 P 40 (Italian adapted Schuko) (#2) in a modern installation.
    VIMAR universale.jpg
    Italian Vimar universale socket accepting CEE 7/4 (German), CEE 7/7 (German/French), CEE 7/16 (Europlug), CEE 7/17 (German/French unearthed), NEMA 1-15 (US/Japan), CEI 23-50 S 11 (10 A) and S 17 (16 A) Italian plugs.
    4box side 4B.AM.H21 28-14.jpg
    4box side socket combining 1 Schuko and 2 CEI 23-50 P 17/11 bipasso (Italian type plugs).

    In modern installations in Italy (and in other countries where Type L plugs are used) it is usual to find sockets that can accept more than one standard.

    The simplest type, designated CEI 23-50 P 17/11, has a central round hole flanked by two figure-8 shaped holes, allowing the insertion of CEI 23-50 S 10 (Italian 10 A plug unearthed), CEI 23-50 S 11 (Italian 10 A plug earthed), CEI 23-50 S 16 (Italian 16 A plug unearthed), CEI 23-50 S 17 (Italian 16 A plug earthed) and CEE 7/16 (Europlug). The advantage of this socket style is its small, compact face; its drawback is that it accepts neither CEE 7/7 nor CEE 7/17, very commonly found in new appliances sold in Italy. Vimar brand claims to have patented this socket first in 1975 [39] with their Bpresa model; however soon other brands started selling similar products, mostly naming them with the generic term presa bipasso (twin-gauge socket) that is now of common use.

    A second, quite common type is called CEI 23-50 P 30 and looks like a Schuko socket, but adds a central earthing hole (optional according to CEI 23-50, but virtually always present). This design can accept CEE 7/4 (German), CEE 7/7 (German/French), CEE 7/16, CEE 7/17 (Konturenstecker, German/French unearthed), CEI 23-50 S 10 and CEI 23-50 S 11 plugs. Its drawback is that it is twice as large as a normal Italian socket, it does not accept 16 A Italian plugs and the price is higher; for those reasons Schuko sockets have been rarely installed in Italy until recent times.[ citation needed ]

    Other types may push compatibility even further. The CEI 23-50 P 40 socket, which is quickly becoming the standard in Italy along with CEI 23-50 P 17/11, accepts CEE 7/4, CEE 7/7, CEE 7/16, CEE 7/17, CEI 23-50 S 10, CEI 23-50 S 11, CEI 23-50 S 16 and CEI 23-50 S 17 plugs; its drawback is that it does not accept SPA 11, SPB 11, SPA 17 and SPB 17 side-entry plugs; however almost no appliance is sold with these types, which are mainly used to replace existing plugs. The Vimar-brand universale (all purpose) socket accepts CEE 7/4, CEE 7/7, CEE 7/16, CEE 7/17, CEI 23-50 S 10, CEI 23-50 S 11, CEI 23-50 S 16, CEI 23-50 S 17 and also NEMA 1-15 (US/Japan) plugs (older versions also had extra holes to accept UK shaver plugs).

    Soviet standard GOST 7396 C 1 unearthed

    This Soviet plug, still widely used in modern Russia, has pin dimensions and spacing equal to the Europlug, but lacks the insulation sleeves. Unlike the Europlug, it is rated 6 A. It has a round body like the French CEE 7/6 or flat body with a round base like CEE 7/17. The round base has no notches. The pins are parallel and do not converge. The body is made of fire resistant thermoset plastic. The corresponding 6 A socket accepts the Europlug, but not others as the 4.5 mm holes are too small to accept the 4.8 mm pins of CEE 7/4, CEE 7/6 or CEE 7/7 plugs.

    There were also moulded rubber plugs available for devices up to 16 A similar to CEE 7/17, but with a round base without any notches. They could be altered to fit a CEE 7/5 or CEE 7/3 socket by cutting notches with a sharp knife.

    Swiss SEV 1011

    Type J: The 10 Ampere SEV 1011:2009 type 13 socket (here: a triple socket) and type 12 plug J plug - 1.jpg
    Type J: The 10 Ampere SEV 1011:2009 type 13 socket (here: a triple socket) and type 12 plug

    The Swiss standard, also used in Liechtenstein, [40] is SN SEV 1011:2009 Plugs and socket-outlets for household and similar purposes. [41] The standard defines a hierarchical system of plugs and sockets with two, three and five pins, and 10 A or 16 A ratings. Sockets will accept plugs with the same or fewer pins and the same or lower ratings. [42]

    SEV 1011:2009, overview of the hierarchical Swiss System SEV 1011 Swiss System Plugs and Sockets.jpg
    SEV 1011:2009, overview of the hierarchical Swiss System

    The three phase variants of the standard are also described at Industrial and multiphase power plugs and sockets § Switzerland: SEV 1011.

    All of the single phase connectors are rated at 250 V. The three-phase connectors are rated at 250 V (phase-to-neutral) / 400 V (phase-to-phase).

    The Swiss standard does not require the use of child protective shutters.

    The Swiss standard was first described in SEV 1011 (ASE1011/1959 SW10A-R). On 4 December 2009, the TK23 Technical Committee issued the new revised edition of the Swiss standard SEV 1011:2009 for 10-A plugs and 11/12 sockets to provide, among other things, improved protection against contact with partially insulated pins can. As of 1 January 2013, imports into Switzerland of Type 11 and Type 12 plugs are only permitted with partially insulated plug pins. After the year 2016, only sockets type 13 with a recessed socket hole may be brought onto the market.

    10 A plugs and sockets (Type J)

    SEV 1011 defines a "Type 1x" series of 10 A plugs and sockets.

    The type 11 plug is unearthed, with two 4 mm diameter round pins spaced 19 mm apart. The type 12 plug adds a central 4 mm diameter round earth pin, offset by 5 mm.

    The type 12 socket has no recess, while the type 13 socket is recessed. Both sockets will accept type 11 and type 12 plugs, and also the 2.5 A Europlug. From 2017 only recessed sockets are permitted to be installed, minimizing the risk of electric shocks. [43]

    Earlier type 11 & 12 plugs had line and neutral pins without sleeved pins, which present a shock hazard when partially inserted into non-recessed sockets. Since 1 January 2013, only type 11 & 12 plugs with line and neutral pins partially sleeved are allowed to be imported and distributed to reduce the risk. [44]

    The IEC type J designation refers to SEV 1011's type 12 plugs and type 13 sockets. [40]

    Unique to Switzerland is a three-phase power socket compatible with single-phase plugs: [42]

    The type 15 plug has three round pins, of the same dimensions as type 12, plus two smaller flat rectangular pins for two additional power phases. The type 15 socket is recessed, and has five openings (three round and two flat rectangular). It will accept plugs of types 11, 12, 15 and the Europlug.

    16 A plugs and sockets

    SEV 1011 also defines a "Type 2x" series of 16 A plugs and sockets. These are the same as their 10 A "Type 1x" counterparts, but replace the round pins with 4 mm × 5 mm rectangular pins. The sockets will accept "Type  1x" plugs.

    The unearthed type 21 plug has two rectangular pins, with centres 19 mm apart. The type 23 plug adds a central rectangular earth pin, offset by 5 mm.

    The recessed type 23 socket will accept plugs of types 11, 12, 21, 23 and the Europlug.

    Again, the three-phase power socket is compatible with single-phase plugs, either of 10 A or 16 A ratings: [42]

    The type 25 plug has three rectangular pins of the same dimensions as type 23, plus two rectangular pins of the same dimensions as type 15. The corresponding type 25 socket is recessed and will accept plugs of types 11, 12, 15, 21, 23, 25 and the Europlug.

    Adaptors etc.

    A 2012 appendix to SEV 1011:2009, SN SEV 1011:2009/A1:2012 Plugs and socket-outlets for household and similar purposes – A1: Multiway and intermediate adaptors, cord sets, cord extension sets, travel adaptors and fixed adaptors [45] defines the requirements applicable to multiway and intermediate adaptors, cord sets, cord extension sets, and travel and fixed adaptors, it covers the electrical safety and user requirements, including the prohibition of stacking (the connection of one adaptor to another). Non-conforming products must be withdrawn from the Swiss market before the end of 2018. [46]

    IEC 60906-1 (Type N)

    In 1986, the International Electrotechnical Commission published IEC 60906-1, a specification for a plug and socket that look similar, but are not identical, to the Swiss plug and socket. This standard was intended to one day become common for all of Europe and other regions with 230 V mains, but the effort to adopt it as a European Union standard was put on hold in the mid-1990s. [47]

    The plug and socket are rated 16 A 250 V a.c. and are intended for use only on systems having nominal voltages between 200 V and 250 V a.c. The plug pins are 4.5 mm in diameter, line and neutral are on centres 19 mm apart. The earth pin is offset 3.0 mm. The line pin is on the left when looking at a socket with the earth pin offset down. Shutters over the line and neutral pins are mandatory.

    The only country to have officially adopted the standard is South Africa as SANS 164-2. [48] [49]

    Brazil developed a plug resembling IEC 60906-1 as the national standard under specification NBR 14136. [16] The NBR 14136 standard has two versions, neither of which has pin dimensions or ratings complying to IEC 60906-1. Use at 125 V is permitted by NBR 14136, which is against the intention of IEC 60906-1.

    China GB 2099.1‐2008 and GB 1002‐2008 (Type A & I)

    Chinese 3-pin socket and compound socket which also accepts NEMA and Europlug (right), and a less common, larger 16 A version (left) China's 3-pin sockets.jpg
    Chinese 3-pin socket and compound socket which also accepts NEMA and Europlug (right), and a less common, larger 16 A version (left)

    The standard for Chinese plugs and sockets (excluding Hong Kong and Macau) is set out in GB  2099.1‐2008 and GB 1002‐2008. As part of China's commitment for entry into the WTO, the new CPCS (Compulsory Product Certification System) has been introduced, and compliant Chinese plugs have been awarded the CCC Mark by this system. The plug is three wire, earthed, rated at 10 A, 250 V and used for Class 1 applications; a slightly larger 16 A version also exists. The nominal pin dimensions of the 10 A version are: 1.5 mm thick by 6.4 mm wide, the line & neutral are 18 mm long, and the earth is 21 mm long. [50] It is similar to the Australian plug. Many 3 pin sockets in China include a physical lockout preventing access to the active and neutral terminals unless an earth pin (which is slightly longer than the other 2 pins) is entered first. China also uses American/Japanese NEMA 1‐15 sockets and plugs for Class-II appliances; a common socket type that also accepts Europlug (type C) is also defined in GB 1002. The voltage at a Chinese socket of any type is 220 V.

    Type I plugs and sockets from different countries have different pin lengths. This means that the uninsulated pins of a Chinese plug may become live while there is still a large enough gap between the faces of the plug and socket to allow a finger to touch the pin.

    Israel SI32 (Type H)

    Two Israeli plugs and one socket. The left plug is the old standard; the one on the right is the 1989 revision. Israeli-type-H-plugs-and-socket.jpg
    Two Israeli plugs and one socket. The left plug is the old standard; the one on the right is the 1989 revision.
    Socket polarity, with wire colour coding. Israel, type H, mains socket polarity.jpg
    Socket polarity, with wire colour coding.

    The plug defined in SI 32 (IS16A-R) is used only in Israel and in the territories of the West Bank and the Gaza Strip. There are two versions: an older one with flat pins, and a newer one with round pins. [51]

    The pre-1989 system has three flat pins in a Y-shape, with line and neutral 19 mm (0.75 in) apart. The plug is rated at 16 A. In 1989 the standard was revised, with three round 4.5 mm (0.177 in) pins in the same locations designed to allow the socket to accept both older and newer Israeli plugs, and also non-earthed Europlugs (often used in Israel for equipment which does not need to be earthed and does not use more current than the Europlug is rated for). [51] Pre-1989 sockets which accept only old-style plugs have become very rare in Israel.

    SI 32 plugs have no sleeve insulation, so when a plug is partially removed its prongs may still be powered although they can be touched by small fingers, metal objects, etc., with a risk of electric shock.

    Sockets have a defined polarity; looking at the front, neutral is to the left, earth at the bottom, and line to the right. [52]

    North American and IEC 60906-2

    Most of North America and Central America, and some of South America, use connectors standardized by the National Electrical Manufacturers Association. The devices are named using the format NEMA n-mmX, where n is an identifier for the configuration of pins and blades, mm is the maximum current rating, and X is either P for plug or R for receptacle. For example, NEMA 5-15R is a configuration type 5 receptacle supporting 15 A. Corresponding P and R versions are designed to be mated. The prefix, L, is added for the locking types; a 15 A 120 V two-pole grounding plug is designated NEMA L5-15P. Twist-locking types are used for additional protection from accidental disconnection, or to prevent interchange with parallel blade types

    Within the series, the arrangement and size of pins will differ, to prevent accidental mating of devices with a higher current draw than the receptacle can support.

    NEMA 1-15 ungrounded (Type A)

    NEMA-1 plug polarized.agr.jpg
    A plug.jpg
    Polarized (left) and unpolarized NEMA 1-15 plugs

    NEMA-1 plugs have two parallel blades and are rated 15 A at 125 volts. They provide no ground connection but will fit a grounding NEMA 5-15 receptacle. Early versions were not polarized, but most plugs are polarized today via a wider neutral blade. (Unpolarized AC adaptors are a common exception.)

    Harvey Hubbell patented a parallel blade plug in 1913, where the blades were equal width (US patent 1064833 [53] ). In 1916 Hubbell received a further patent for a polarized version where one blade was both longer and wider than the other (US patent 1180648 [54] ), in the polarized version of NEMA 1-15 both blades are the same length, only the width varies.

    Ungrounded NEMA-1 outlets are not permitted in new construction in the United States and Canada, but can still be found in older buildings.

    NEMA 5-15 grounded (Type B)

    Domestic AC Type B USA.jpg
    NEMA 5-15 Outlet 120V-15A.jpg
    NEMA 5-15 plug, left. Decorative-style duplex socket, with orientation as specified in NECA 130-2010, centre. Ordinary duplex socket, with orientation typically found, right. Photos are different scale – parallel blades are on 1/2 inch (12.7 mm) centres.

    The NEMA 5-15 plug has two flat parallel blades like NEMA 1-15, but also adds a ground (earth) pin. [55] It is rated 15 A at 125 volts. The ground (earth) pin is longer than the line and neutral blades, so the device is grounded before the power is connected. Both current-carrying blades on grounding plugs are normally narrow, since the ground (earth) pin enforces polarity.

    This socket is recommended in IEC standard 60906-2 for 120-volt 60 Hz installations.

    In 46 of the 50 United States [56] and all of Canada, tamper-resistant sockets are now required in new residential construction. These have shutters to prevent contact by objects like keys or paper clips inserted into the socket. [57]

    In stage lighting, this connector is sometimes known as PBG for Parallel Blade with Ground (earth), Edison or Hubbell, the name of a common manufacturer. [58]

    NEMA 5-20

    5-20RA (Canada) or 5-20R (US) T-slot socket mounted with the earth hole up. The neutral connection is the wider T-shaped slot on the right. Electrical outlet with label.jpg
    5-20RA (Canada) or 5-20R (US) T-slot socket mounted with the earth hole up. The neutral connection is the wider T-shaped slot on the right.

    As NEMA 5 currents increase, changes are made to the plug's neutral blade so that it will not fit into sockets rated for a lower current. Some sockets rated for higher currents are designed to accept many shapes for the neutral blade, so that both high and low draw devices are compatible with it.

    The NEMA 5-20 AP variant has a horizontal neutral blade (in a plane that would intersect the hot blade). The receptacle has a T-slot for the neutral blade which accepts either 15 A parallel-blade plugs or 20 A plugs.

    NEMA 14-30

    A 30 A, 4-wire single-phase grounding socket is often used for electric clothes dryers. 240 volts from the split phase system is used for the heating elements, and the motor and controls run on 120 volts.

    NEMA 14-50

    This is a 50 A, 4-wire grounding socket usually installed in kitchens and used for electric cooking ranges and ovens supplied with 240 V . Many plug-in electric cars also use this type of socket for recharging in the owner's garage [ citation needed ]). It is also commonly found in RV parks to provide electricity to recreational vehicles. These plugs have a straight neutral blade that will not fit in a NEMA 14-30 receptacle.

    JIS C 8303, Class II unearthed

    Japanese socket with earth post, for a washing machine OutletPlug.jpg
    Japanese socket with earth post, for a washing machine
    Japanese socket with earth post and earth connector, for an air conditioner Japanese air conditioner electrical outlet.jpg
    Japanese socket with earth post and earth connector, for an air conditioner
    Japanese 200 V socket with earth post, for an air conditioner Japanese air conditioner electrical outlet 200v.jpg
    Japanese 200 V socket with earth post, for an air conditioner

    The Japanese plug and socket appear physically identical to NEMA 1-15. The Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements, and mandatory testing and approval by METI or JIS. [59]

    Older Japanese sockets and multi-plug adaptors are unpolarized – the slots in the sockets are the same size – and will accept only unpolarized plugs. Japanese plugs generally fit into most North American sockets without modification, but polarized North American plugs may require adaptors or replacement non-polarized plugs to connect to older Japanese sockets. In Japan the voltage is 100 V, and the frequency is either 50 Hz (East Japan) or 60 Hz (West Japan) depending on whether the customer is located on the Osaka or Tokyo grid. [60] [61] Therefore, some North American devices which can be physically plugged into Japanese sockets may not function properly.

    JIS C 8303, Class I earthed

    Japan also uses a grounded plug similar to the North American NEMA 5-15. [59] However, it is less common than its NEMA 1-15 equivalent. Since 2005, new Japanese homes are required to have class I grounded sockets for connecting domestic appliances. This rule does not apply for sockets not intended to be used for domestic appliances, but it is strongly advised to have class I sockets throughout the home. [62]

    Thai 3 pin plug TIS 166-2549

    TIS 166-2549 plug Thai TIS 166-2549 mains plug.jpg
    TIS 166-2549 plug

    Thai Industrial Standard (TIS) 166-2547 and its subsequent update TIS 166-2549 [63] replaced prior standards which were based on NEMA 1-15 and 5-15, as Thailand uses 220 V electricity. The plug has two round power pins 4.8 mm in diameter and 19 mm in length, insulated for 10 mm and spaced 19 mm apart, with an earthing pin of the same diameter and 21.4 mm in length, located 11.89 mm from the line connecting the two power pins. The earth pin spacing corresponds to that of NEMA 5 and provides compatibility with prior hybrid three-pin sockets, which accept NEMA 1-15, NEMA 5-15 and Europlugs, all of which have been variably used in Thailand. The hybrid socket is also defined in TIS 166-2547, in addition to a plain three-round-pin socket, with plans to replace the former and phase out support for NEMA-compatible plugs. Sockets are polarised (as in NEMA 5-15). [64] The plug is similar to, but not interchangeable with, the Israeli SI32 plug. The Thai plug has not been designated with a letter code at IEC World Plugs, [11] but is sometimes referred to and sold as "Type O". [65] [66] [67] [68] [69]

    Comparison and compatibility of standard types

    IEC
    World
    Plugs
    Type [lower-alpha 1]
    StandardOriginRatingEarthed

    (Grounded)

    PolarisedFusedInsulated
    pins
    Socket
    accepts
    Europlug
    ANEMA 1-15 unpolarisedAmerican15 A125 VNoNoNoNoNo
    NEMA 1-15 polarisedAmerican15 A125 VNoYesNoNoNo
    JIS C 8303, Class IIJapanese15 A125 VNoNoNoNoNo
    BNEMA 5-15American15 A125 VYes [lower-alpha 2] YesNoNoNo
    NEMA 5-20American20 A125 VYes [lower-alpha 2] YesNoNoNo
    JIS C 8303, Class IJapanese15 A125 VYes [lower-alpha 2] YesNoNoNo
    C CEE 7/16 "Europlug"2.5 A250 VNoNoNoYesN/A [lower-alpha 3]
    -CEE 7/17 plug [lower-alpha 4] French /
    German hybrid
    16 A250 VNoNo [lower-alpha 5] NoNoN/A [lower-alpha 3]
    -CEE 7/1 socket & CEE 7/2 plugN/A10 A
    16 A
    250 VNo [lower-alpha 6] NoNoNoYes
    - GOST 7396 C 1Soviet/Russian6 A
    16 A
    250 VNoNoNoNoYes
    - BS 4573 British0.2 A250 VNoNoNoYesNo
    Socket only; plug is
    unspecified [lower-alpha 7]
    D BS 546 British5 A250 VYesYesOptionalOptionalNo
    IS 1293 and
    SANS 164-3
    Indian and
    South African
    (respectively)
    6 A250 VYesYesOptionalOptionalNo
    ECEE 7/5 socket & CEE 7/6 plug [lower-alpha 8] [lower-alpha 4] French16 A250 VYes [lower-alpha 2] Yes [lower-alpha 9] NoNo [lower-alpha 10] Yes
    FCEE 7/3 socket & CEE 7/4 plug [lower-alpha 8] [lower-alpha 4] German
    "Schuko"
    16 A250 VYes [lower-alpha 2] NoNoNo [lower-alpha 10] Yes
    -CEE 7/7 plug [lower-alpha 8] French /
    German hybrid
    16 A250 VYesNoNoNo [lower-alpha 10] N/A [lower-alpha 3]
    G BS 1363, IS 401 & IS 411, MS 589, SS 145British13 A [lower-alpha 11] 250 VYesYesYesYesNo
    HSI 32Israeli16 A250 VYesYes [lower-alpha 12] NoNoYes
    I AS/NZS 3112 Australian
    and
    New Zealander
    10 A
    15 A
    20 A
    25 A
    32 A
    250 VYes [lower-alpha 2] YesNoYesNo
    GB 1002 and
    GB 2099.1
    Chinese10 A250 VYesYesNoNoNo
    IRAM 2073Argentinian10 A250 VYesYesNoNoNo
    JSEV 1011:2009, Typ 12 plug and Typ 13 socketSwiss10 A250 VYes [lower-alpha 2] YesNoYes [lower-alpha 13] Yes
    K107-2-D1Danish13 A250 VYes [lower-alpha 2] YesNoNoYes
    L [lower-alpha 14] CEI 23-50 (formerly CEI 23-16)Italian10 A250 VYes [lower-alpha 2] NoNoYesYes
    CEI 23-50 (formerly CEI 23-16)Italian16 A250 VYes [lower-alpha 2] NoNoYesNo
    M BS 546 British15 A250 VYesYesOptionalOptionalNo
    IS 1293 and
    SANS 164-1
    Indian and
    South African
    (respectively)
    16 A250 VYesYesOptionalOptionalNo
    NNBR 14136 2-pinBrazilian10 A
    20 A
    250 VNoNoNoYesYes
    NBR 14136 3-pinBrazilian10 A
    20 A
    250 VYes [lower-alpha 2] YesNoYesYes
    SANS 164-2 2-pinSouth African16 A250 VNoNoNoYesYes
    SANS 164-2 3-pinSouth African16 A250 VYes [lower-alpha 2] YesNoYesYes
    -TIS 166-2549Thai16 A250 VYesYesNoYesYes
    IEC
    World
    Plugs
    Type [lower-alpha 1]
    StandardOriginRatingEarthedPolarisedFusedInsulated
    pins
    Socket
    accepts
    Europlug
    1. 1 2 Type letters are from the International Electrotechnical Commission (IEC) Web site [11] that provides classification letters similar to a United States Department of Commerce publication [12] that sees widespread but not universal use to differentiate plug and socket types based on rough mechanical compatibility. Most common household plugs have an associated letter.
    2. 1 2 3 4 5 6 7 8 9 10 11 12 Will accept unearthed plugs.
    3. 1 2 3 Standard does not define a socket.
    4. 1 2 3 CEE 7/17 specifies an unearthed hybrid plug that will fit into both the CEE 7/3 and CEE 7/5 sockets.
    5. There are some CEE 7/17 plugs with special shape which are polarised when used with CEE 7/5 sockets (mechanically only).
    6. CEE 7/1 socket accepts earthed CEE 7/3, CEE 7/5 and CEE 7/7 plugs but provides no earth connection.
    7. BS 4573 and BS EN 61558-2-5 do not explicitly specify a current rating for a compliant plug, see BS 4573 section of British and compatible standards.
    8. 1 2 3 CEE 7/7 specifies an earthed hybrid plug that will fit into both the CEE 7/3 and CEE 7/5 sockets.
    9. Plug can only be inserted one way with French CEE 7/5, but lack of wiring convention means that the system is not polarized.
    10. 1 2 3 The recess provided by CEE 7/3 and CEE 7/5 sockets offers protection against touching the live pins of CEE 7/4, CEE 7/6 and CEE 7/7 plugs. When used in CEE 7/1 (unearthed) sockets, or "universal adaptors" there is no protection for those plugs.
    11. The actual rating of non-rewirable plugs is marked according to the fuse fitted by the cord set manufacturer, the fuse rating being determined by the rating of the flexible cable.
    12. Polarized on earthed versions only.
    13. Import of plugs with non-partially-insulated pins no longer allowed after 2012.
    14. Type L comes in two variations with ratings of 10 A & 16 A having different pin diameters and spacing from each other.

    Compatibility

    Plugs of type D, G, and M are physically incompatible with any other type other than their own.
    3-pin plugs of type H, J, K, L, N, and Thai are only compatible with sockets of the same letter type.
    Not all plugs with a given letter are entirely compatible with a socket of the same letter.:

    Physical compatibility of 2-pin European style plugs with selected sockets
    Remarks:
    Does not fit means that the plug will not fit to the socket. No means that, along with the plug not fitting into the socket, the socket/plug-combination is not electrically compatible regarding the definitions of the involved standards. Thus meaning the original intention to physically prevent the combination of incompatible systems is effective.
    Socket
    Unearthed PlugsEarthed Plugs [lower-alpha 1]
    -NC-EFE/F
    BS 4573 (shaver) GOST 7396 C1 SANS 164-2
    (2-pin)
    NBR 14136
    (2-pin)
    CEE 7/16 Alt. II CEE 7/16 Alt. I CEE 7/2 CEE 7/17 CEE 7/6 CEE 7/4 CEE 7/7
    BritishRussianSouth AfricanBrazilian"Europlug"FrenchGerman "Schuko"French / German hybrid
    TypeStandardOriginEarthed?Current Rating (A)0.261616102.52.51616161616
    - CEE 7/1 -No16Does not fitYesYesYesYesYesYesYesYesFits, but unearthed!Fits, but unearthed!Fits, but unearthed!
    E CEE 7/5 FrenchYes16Does not fitDoes not fitDoes not fitYesYesYesYesDoes not fitYesYesDoes not fitYes
    F CEE 7/3 German "Schuko"Yes16Does not fitDoes not fitDoes not fitYesYesYesYesDoes not fitYesDoes not fitYesYes
    HNew Post-1989 SI 32IsraeliYes16Does not fitYesDoes not fitYesYesYesYesDoes not fitDoes not fitNoNoNo
    JSEV 1011:2009 Type 13 socketSwissYes10Does not fitDoes not fitNoNoYesYesDoes not fitNoNoNoNoNo
    K107-2-D1DanishYes13Does not fitYesFits, but with too high rating!Fits, but with too high rating!YesYesYesFits, but with too high rating!Fits, but with too high rating!Fits, but with too high rating and unearthed!Fits, but with too high rating and unearthed!Fits, but with too high rating and unearthed!
    L CEI 23-50 P 10 (unearthed) / P 11 (earthed)ItalianBoth Occur10Does not fitYesNoNoYesYesYesNoNoNoNoNo
    CEI 23-50 P 17ItalianYes16Does not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fitDoes not fit
    N NBR 14136 BrazilianBoth Occur10Does not fitDoes not fitNoNoYesYesDoes not fitNoNoNoNoNo
    20Does not fitDoes not fitDoes not fitYesYesYesDoes not fitDoes not fitDoes not fitNoNoNo
    SANS 164-2 South AfricanBoth Occur16Does not fitDoes not fitDoes not fitYesYesYesDoes not fitDoes not fitDoes not fitNoNoNo
    - TIS 166-2549 [lower-alpha 2] ThaiYes16Does not fitYesYesYesYesYesYesYesYesFits, but unearthed!Fits, but unearthed!Fits, but unearthed!
    - GOST 7396 C1 RussianNo6Does not fitYesNoFits, but with too high rating!Fits, but with too high rating!YesYesNoNoNoNoNo
    16Does not fitYesYesYesYesYesYesYesYesFits, but unearthed!Fits, but unearthed!Fits, but unearthed!
    - BS 4573 (shaver)BritishNo0.2YesNoNoNoNoNoNoNoNoNoNoNo
    Notes:
    1. 3-pin plugs of type H, J, K, L, N, and Thai are only compatible with sockets of the same letter type.
    2. TIS 166-2549 standard also specifies a universal socket that accepts type A, B, C, and Thai plugs.

    Adaptors

    A travel adaptor for "Type M" (16 A SANS 164-1) sockets from South Africa. Type M travel adaptor.jpg
    A travel adaptor for "Type M" (16 A SANS 164-1) sockets from South Africa.

    Adaptors between standards are not included in the standards, so have no formal quality criteria defined. Physical compatibility does not ensure that the appliance and socket match in frequency or voltage. Adaptors allow travellers to connect devices to foreign sockets, but do not change voltage or frequency. A voltage converter is required for electrical compatibility in places with a different voltage than the device is designed for. Mismatch in frequency between supply and appliances may still cause problems even at the correct voltage.

    Multisocket adaptors allow the connection of two or more plugs to a single socket. They are manufactured in various configurations, depending on the country and the region in which they are used, with various ratings. In Europe for example, they are called double or triple adaptors, and transform one socket into a multiple socket. This allows connecting more than one electrical consumer item to one single socket and is mainly used for low power devices (TV sets, table lamps, computers, etc.). They are usually rated at 6 A 250 V, 10 A 250 V, or 16 A 250 V, however this is the general rating of the adaptor (for example, if we have an adaptor for four sockets and it is marked 16 A 250 V, this means that the adaptor should not be loaded more than 16 A, whether one, two, three or all sockets are used. Some people overload them, thus leading to accidents). In some countries these adaptors are banned and are not available in shops, as they may lead to fires due to overloading them. Adaptors can be made with ceramic, Bakelite, or other plastic bodies.

    Unusual types

    Lampholder plug

    Italian bypass lampholder plugs with Edison screw mount. Left: early type (porcelain and brass, c. 1930); right: late type (black plastic, c. 1970) Lampholder plugs.jpg
    Italian bypass lampholder plugs with Edison screw mount. Left: early type (porcelain and brass, c. 1930); right: late type (black plastic, c. 1970)

    A lampholder plug fits into the bayonet cap or Edison screw socket of a lampholder in place of a light bulb and enables an electrical appliance to be powered from a wall or ceiling light fitting. As mentioned in Early History above, they were first introduced in the late 1800s and in use to the 1960s in situations where wall sockets were scarce and sometimes non-existent in some rooms (bathrooms, cellars, attics, etc.). Also, as in some countries (such as Italy) electricity was supplied on a "split tariff" basis with electricity for lighting being charged at a lower rate than that for other purposes, lampholder plugs enabled the consumers to reduce their electricity costs and were thus in broad use.

    Lampholder plugs were and are rarely fused.

    In the UK, lighting circuits are protected with a 5 A fuse or 6 A miniature circuit breaker. [70] Wiring regulations in the UK and some other countries no longer approve lampholder plugs because of the risks of overheating and fire.

    Edison screw lampholder adaptors (for NEMA 1-15 plugs) are still easily found and commonly used in the Americas.

    NEMA 2‐15 and 2‐20

    These unearthed plugs with two flat blades are intended for 240 volt circuits; the sockets are no longer permitted in new construction. In some cases these plugs can be inserted into incorrect-voltage sockets.

    Soviet adaptor plugs

    Soviet adaptor plug Soviet power plug.JPG
    Soviet adaptor plug

    Some appliances sold in the Soviet Union had a flat unearthed plug with an additional pass-through socket on the top, allowing a stacked arrangement of plugs. This design was very useful, because the usual Soviet apartment of the 1960s had very few sockets, but somewhat unsafe; the brass cylinders of the secondary socket were uncovered at the ends (to allow them to be unscrewed easily), recessed by only 3 mm, and provided bad contact because they relied on the secondary plug's bisected expanding pins. The pins of the secondary plug (which lacked insulation sleeves) could not be inserted into the cylindrical sockets completely, leaving a 5 mm gap between the primary and secondary plugs. The adaptors were mostly used for low power appliances (for example, connecting both a table lamp and a radio to a socket).

    UK Walsall Gauge plug

    Walsall Gauge 13 A plug (bottom) compared to regular BS 1363 plug WG13 PICT6943.jpg
    Walsall Gauge 13 A plug (bottom) compared to regular BS 1363 plug

    Unlike the standard BS 1363 plugs found in the UK, the earth pin is on a horizontal axis and the line and neutral pins on a vertical axis. This style of plug/socket was used by university laboratories (from batteries) and the BBC, and is still in use on parts of the London Underground for 110 V AC voltage supply. [71] In the 1960s they were used for 240 V DC in the Power laboratory of the Electrical Engineering department of what was then University College, Cardiff. Power was supplied by the public 240 V DC mains which remained available in addition to the 240 V AC mains until circa 1969, and thereafter from in-house rectifiers. They were also used in the Ministry of Defence Main Building on circuits powered from the standby generators to stop staff from plugging in unauthorised devices. They were also known to be used in some British Rail offices for the same reason.

    Italian BTicino brand Magic security connector

    Bticino Magic 1.jpg
    Bticino Magic 2.jpg
    Bticino Magic 3.jpg
    Left: Bticino Magic Security socket, detail.
    Centre: assortment of Magic Security sockets (in orange, the industrial three-phase type).
    Right: assortment of Magic Security plugs.

    This style of connector, produced by Italian manufacturer BTicino, appeared in the 1960s and was intended as an alternative to the Europlug or CEI 23-16 connectors then in use. [72] The socket is an almost rectangular socket, with one or more lateral key pins and indentations to prevent inverting the polarised plug, or connecting plugs and sockets with different current ratings. At least four models were produced: three single-phase general purpose connectors rated respectively 10 A, 16 A and 20 A; plus a three-phase industrial connector rated 10 A; all of them have different key-pin positioning so plugs and sockets cannot be mismatched. [73] The socket is closed by a safety lid (bearing the word ‘’Magic’’ on it) which can be opened only with an even pressure on its surface, thus preventing the insertion of objects (except the plug itself) inside the socket. The contacts are positioned on both sides of the plug; the plug is energised only when it is inserted fully into the socket.

    On the left a BTicino Magic Security plug (10 A), on the right a type L to Magic Security plug adaptor Spina magic 02.jpg
    On the left a BTicino Magic Security plug (10 A), on the right a type L to Magic Security plug adaptor

    The obvious drawback of the system is that it is not compatible with Italian 10 A and 16 A plugs, as well as with Europlugs. As household appliances were never sold fitted with these security plugs and the use of adaptors would defeat all of the newly introduced safety features, once this system is adopted all standard plugs must be cut off and replaced with the appropriate security connector. However, the Magic security system had some success at first because its enhanced safety features appealed to customers; standard connectors of the day were considered not safe enough. [72] The decline of the system occurred when safety lids similar to the Magic type were developed (Vimar Sicury [74] ) and then applied to standard sockets by third brands and by BTicino itself.

    In Italy, the system was never definitively abandoned and, though very rarely seen today, is still marked as available in BTicino’s products catalogue, [75] (except for the three-phase version, which stopped production in July 2011).

    In Chile, 10 A Magic connectors are commonly used for computer/laboratory power networks, as well as for communications or data equipment. This allows delicate electronics equipment to be connected to an independent circuit breaker, usually including a surge protector or an uninterruptible power supply backup. The different style of plug makes it more difficult for office workers to connect computer equipment to a standard unprotected power line, or to overload the UPS by connecting other office appliances.

    In Iceland, Magic plugs were widely used in homes and businesses alongside Europlug and Schuko installations. Their installation in new homes was still quite common even in the late 1980s.

    Single phase electric stove plugs and sockets

    Plug (sheet V) and socket (sheet VI) to French standard NF C 61-315 (400 V, 32 A) Power connector Legrand 32A.jpg
    Plug (sheet V) and socket (sheet VI) to French standard NF C 61-315 (400 V, 32 A)
    Russian stove plug and socket.jpg
    Russian stove outlet.jpg
    Russian stove plug.jpg
    Russian stove connectors rated 250 V 25 A AC. Left: plug and socket. Center: Socket. Right: Plug.

    The plugs and sockets used to power electric stoves from a single-phase line have to be rated for greater current values than those used with three-phase supply because all the power has to be transferred through two contacts, not three. If not hardwired to the supply, electric stoves may be connected to the mains with an appropriate high power connector. Some countries do not have wiring regulations for single-phase electric stoves. In Russia an electric stove can often be seen connected with a 25 to 32 A connector.

    In Norway and parts of Sweden a 25 A grounded connector, rectangular shaped with rounded corners, is used for single phase stoves. The connector has three rectangular pins in a row, with the grounding pin longer than other two. The corresponding socket is recessed to prevent shocks. The Norwegian standard is NEK 502:2005 – standard sheet X (socket) and sheet XI (plug). They are also known as the two pole and earth variants of CEE 7/10 (socket) and CEE 7/11 (plug).

    Industrial and multiphase

    Plug and socket 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 security and safety. For example, a high-power plug may include a locking ring or twist-lock feature to prevent accidental disconnection. A socket 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 (such as mines) may include small supervisory contacts that check the integrity of the earthing conductor.

    See also

    Related Research Articles

    A DC connector is an electrical connector for supplying direct current (DC) power.

    IEC 60320 Appliance couplers for household and similar general purposes is a set of standards from the International Electrotechnical Commission (IEC) specifying non-locking appliance and interconnection couplers for connecting power supply cords to electrical appliances of voltage not exceeding 250 V (a.c.) and rated current not exceeding 16 A. Different types of connector are specified for different combinations of current, temperature and earthing requirements. Unlike IEC 60309 connectors, they are not coded for voltage; users must ensure that the voltage rating of the equipment is compatible with the mains supply.

    Power cord power cable

    A power cord, line cord, or mains cable is an electrical cable that temporarily connects an appliance to the mains electricity supply via a wall socket or extension cord. The terms are generally used for cables using a power plug to connect to a single-phase alternating current power source at the local line voltage—(generally 100 to 240 volts, depending on the location). The terms power cable, mains lead, flex or kettle lead are also used. A lamp cord is a light-weight, ungrounded, single-insulated two-wire cord used for small loads such as a table or floor lamp.

    Schuko type of AC power plug and socket

    "Schuko" is a registered trademark referring to a system of AC power plugs and sockets that is defined as "CEE 7/3" (sockets) and "CEE 7/4" (plugs). A Schuko plug features two round pins of 4.8 mm diameter for the line and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth (ground). The socket has a predominantly circular recess which is 17.5 mm deep with two symmetrical round apertures and two earthing clips on the sides of the socket positioned to ensure that the earth is always engaged before live pin contact is made. Schuko plugs and sockets are symmetric AC connectors. They can be mated in two ways, therefore line can be connected to either pin of the appliance plug. As with most types of European sockets, Schuko sockets can accept Europlugs. Schuko plugs are considered a very safe design when used with Schuko sockets, but they can also mate with other sockets to give an unsafe result.

    Banana connector single-wire electrical connector used for joining wires to equipment

    A banana connector is a single-wire electrical connector used for joining wires to equipment. The term 4 mm connector is also used, especially in Europe, although not all banana connectors will mate with 4 mm parts, and 2 mm banana connectors exist. Various styles of banana plug contacts exist, all based on the concept of spring metal applying outward force into the unsprung cylindrical jack to produce a snug fit with good electrical conductivity. Common types include: a solid pin split lengthwise and splayed slightly, a tip of four leaf springs, a cylinder with a single leaf spring on one side, a bundle of stiff wire, a central pin surrounded by a multiply-slit cylinder with a central bulge, or simple sheet spring metal rolled into a nearly complete cylinder. The plugs are frequently used to terminate patch cords for electronic test equipment, while sheathed banana plugs are common on multimeter probe leads.

    IEC 60309 Standard for industrial and multi-phase sockets in Europe

    IEC 60309 is an international standard from the International Electrotechnical Commission (IEC) for "plugs, socket-outlets and couplers for industrial purposes". The maximum voltage allowed by the standard is 1000 V DC or AC; the maximum current, 800 A; and the maximum frequency, 500 Hz. The ambient temperature range is −25 °C to 40 °C.

    Mains electricity by country includes a list of countries and territories, with the plugs, voltages and frequencies they commonly use for providing electrical power to appliances, equipment, and lighting typically found in homes and offices. Some countries have more than one voltage available. For example, in North America most sockets are attached to a 120 V supply, but there is a 240 V supply available for large appliances. Often different sockets are mandated for different voltage or current levels.

    Industrial and multiphase power plugs and sockets

    Industrial and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets. They are generally used in polyphase systems, with high currents, or when protection from environmental hazards is required. Industrial outlets may have weatherproof covers, waterproofing sleeves, or may be interlocked with a switch to prevent accidental disconnection of an energized plug. Some types of connectors are approved for hazardous areas such as coal mines or petrochemical plants, where flammable gas may be present.

    Electrical wiring in the United Kingdom is commonly understood to be an electrical installation for operation by end users within domestic, commercial, industrial, and other buildings, and also in special installations and locations, such as marinas or caravan parks. It does not normally cover the transmission of electrical power to them.

    Europlug non-rewirable flat, two-pole domestic AC power plug

    The Europlug is a flat, two-pole, round-pin domestic AC power plug, rated for voltages up to 250 V and currents up to 2.5 A. It is a compromise design intended to connect low-power Class II appliances safely to the many different forms of round-pin domestic power socket used across Europe. However, it is not compatible with the rectangular-pin BS 1363 sockets found in Cyprus, Gibraltar, Ireland, Malta and the United Kingdom. Europlugs are non-rewirable and must be supplied attached to a power cord.

    IEC 60906-1

    IEC 60906-1 is an international standard designed "to provide a standard for a safe, compact and practical 16 A 250 V AC system of plugs and socket-outlets that could be accepted by many countries as their national standard, even if not in the near future." The standard was originally published by the International Electrotechnical Commission in 1986; the current edition is ed2.0 published in 2009. Although it looks similar to the Swiss SEV 1011 plug, its dimensions are different. As of July 2014, only South Africa has introduced a standard based closely on IEC 60906-1. Brazil used it as the basis for its NBR 14136 standard, but this is not compatible with IEC 60906-1. In 2017 the European Union (EU) published recommendations advising against the harmonisation of domestic plug and socket systems in the EU.

    AS/NZS 3112 AC power plug and socket used in Australia and New Zealand

    AS/NZS 3112 is the harmonised Australian and New Zealand standard for AC power plugs and sockets. The plug and socket configuration, consisting of two flat pins forming an inverted V-shape plus a vertical earthing pin, is used in Australia, New Zealand, Fiji, Tonga, Solomon Islands, Papua New Guinea and several other Pacific island countries. The International Electrotechnical Commission (IEC) "world plugs" Web site calls this plug Type I.

    GOST 7396 is a series of Soviet and later Russian standards that specify basic dimensions and safety requirements for power plugs and sockets used in Russia and other former Soviet Republics, as well as for export to markets that use American or British plugs.

    NEMA connector type of power plugs standardized by the National Electrical Manufacturers Association

    NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA wiring devices are made in current ratings from 15 to 60 amperes (A), with voltage ratings from 125 to 600 volts (V). Different combinations of contact blade widths, shapes, orientation, and dimensions create non-interchangeable connectors that are unique for each combination of voltage, electric current carrying capacity, and grounding system.

    Coaxial power connector electrical connector for low voltage power

    A coaxial power connector is an electrical power connector used for attaching extra-low voltage devices such as consumer electronics to external electricity. Also known as barrel connectors, concentric barrel connectors or tip connectors, these small cylindrical connectors come in an enormous variety of sizes.

    IEC 62196

    IEC 62196Plugs, socket-outlets, vehicle connectors and vehicle inlets – Conductive charging of electric vehicles, also known as CCS Combo, is a series of international standards that define requirements and tests for plugs, socket-outlets, vehicle connectors and vehicle inlets for conductive charging of electric vehicles and is maintained by the technical subcommittee SC 23H “Plugs, Socket-outlets and Couplers for industrial and similar applications, and for Electric Vehicles” of the International Electrotechnical Commission (IEC).

    SANS 164

    South African National Standard 164: Plugs and socket outlets for household and similar purposes for use in South Africa is the South African Bureau of Standards' standard for domestic AC power plugs and sockets. As a former British colony, South Africa's electricity standards are of British derivation, and it uses 220/230 V at 50 Hz AC.

    Plugs and sockets for electrical appliances not hardwired to mains electricity originated in Britain in the 1880s and were initially two-pin designs. These were usually sold as a mating pair, but gradually de facto and then official standards arose to enable the interchange of compatible devices. British standards have proliferated throughout large parts of the former British Empire.

    Type 2 connector Electric vehicle charging connector in Europe

    The IEC 62196 Type 2 connector is used for charging electric cars within Europe. The connector is circular in shape, with a flattened top edge and originally specified for charging battery electric vehicles at 3–50 kilowatts, with a plug modified by Tesla capable of outputting 120 kilowatts. Electric power is provided as single-phase or three-phase alternating current (AC), or direct current (DC). In January 2013, the IEC 62196 Type 2 connector was selected by the European Commission as official charging plug within the European Union. It has since been adopted as the recommended connector in some countries outside of Europe, including New Zealand.

    This is a history of AC power plugs and sockets. Plugs and sockets for portable appliances started becoming available in the 1880s. A proliferation of types developed to address the issues of convenience and protection from electric shock. Today there are approximately 20 types in common use around the world, and many obsolete socket types are still found in older buildings.

    References

    1. Smart Guide Wiring: step-by-step projects, Fran J. Donegan, Creative Homeowner Press, 2004, p.74 (retrieved 2 February 2012 from Google Books)
    2. John Mellanby (1957). The History of Electric Wiring. London: Macdonald.
    3. Alert noting non-compliant power strips
    4. Sri Lanka Sets National Standard for Plugs and Socket Outlets – Standardized on Type G; sale of non-compliant sockets is banned as of August, 2018, and buildings must re-wire by August, 2038.
    5. James S. Jennings. "Army Sustainment: The Three Most Common Electrical Safety Issues in Deployed Environments". Archived from the original on 2012-02-23.
    6. "Universal Sockets Are Unsafe". Interpower Corporation. Interpower. Retrieved 6 July 2018.
    7. "Universal AC Outlet • Setup Guide" (PDF). Anaheim, CA: Extron Electronics. November 2017. 68-1638-01 Rev. F. Retrieved 2018-05-21.
    8. Using electricity on a campsite Camping and Caravanning Club
    9. Electricity on European Campsites Camping and Caravanning Club (UK, so "European" means mainland Europe)
    10. IEC 61558-2-5
    11. 1 2 3 4 World Plugs Retrieved on 2015-03-27.
    12. 1 2 The letter system first appeared in such guides in 1967 (Electric Current Abroad. United States Department of Commerce , 1967. Retrieved on 2013-12-14.) which designated types A 2-pin US, B (BS 546), and C (BS 1363). The 1984 edition (Electric Current Abroad. United States Department of Commerce , 1984. Retrieved on 2013-12-14.) uses the letters A to G in the same manner as they are used today, and the last revision of the print series was in 1998 ( "Electric Current Abroad" (PDF). US Department of Commerce, International Trade Administration (retrieved 9 October 2015). 2002.). The International Trade Administration of the US Department of Commerce now publishes a web version: Electric Current Worldwide, which differs slightly from the IEC list and from Wikipedia's list at Mains electricity by country.
    13. ftp://ftp.cencenelec.eu/CENELEC/TCs/61/PlugsSockets.pdf Plugs and socket types in each CENELEC country, Retrieved 15 February 2012.
    14. AS/NZS 3112:2004, Approval and test specification – Plugs and socket-outlets, Standards Australia and Standards New Zealand
    15. "Mains Plugs with Insulated Pins. Australian Standards AS/NZS3112:2000 & AS/NZS3112:2004 refer [sic]". Access Communications. 19 April 2007.
    16. 1 2 NBR 14136:2002 – Plugues e tomadas para uso doméstico e análogo – Padronização[Plugs and socket-outlets for household use and similar purposes – Specification] (in Portuguese), BR: ABNT, 2002
    17. "Norma ABNT NBR 14136:2002" (in Portuguese). BR: Projeto de redes.
    18. "Archived copy". Archived from the original on 5 March 2016. Retrieved 2015-12-01.CS1 maint: Archived copy as title (link) 9) Aquele fiozinho que tem pendurado atrás da minha geladeira, vai desaparecer?
    19. "World Plugs". International Electrotechnical Commission (IEC). Retrieved 27 August 2014.
    20. BS 1363 (1995), BS 1363:1995 "13 A plugs, socket-outlets, adaptors and connection units", British Standards Institute.
    21. BS 4573 (1970), British Standard Specification for two-pin reversible plugs and shaver socket-outlets, British Standards Institution.
    22. "IECEE CEE-7 ed2.0" . Retrieved 1 March 2015.
    23. "IEC/TR 60083: Technical Report" (PDF). Retrieved 2 March 2015.
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