Power Strip
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A power strip is a block of electrical sockets that attaches to the end of a flexible
cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
(typically with a
mains plug AC power plugs and sockets connect electric equipment to the alternating current (AC) mains electricity power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and current rating, shape, si ...
on the other end), allowing multiple electrical devices to be powered from a single electrical socket. Power strips are often used when many electrical devices are in proximity, such as for
audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...
,
video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syste ...
,
computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
systems, appliances,
power tool A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labor used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed ...
s, and
lighting Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylig ...
. Power strips often include a
circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the risk ...
to interrupt the
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
in case of an overload or a short circuit. Some power strips provide protection against electrical power surges. Typical housing styles include strip, rack-mount, under-monitor and direct plug-in.


Control

Some power strips include a master
switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
to turn all devices on and off. This can be used with simple devices, such as lights, but not with most computers, which must use shutdown commands from the software. Computers may have open files, which may be damaged if the power is simply turned off. Some power strips have individually switched outlets. " Master/slave" strips can detect one "master" device being turned off (such as the PC itself in a computer setup, or a TV in a home theatre) and turn everything else on or off accordingly. Remote control strips are used in
data center A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunic ...
s, to allow computer systems or other devices to be remotely restarted, often over the Internet (although this leaves them vulnerable to outside attacks).


Indication

Many power strips have a
neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
or
LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
indicator light or one per output socket to show when power is on. Better-quality surge-protected strips have additional lights to indicate the status of the surge protection system, however these are not always reliable as an indicator.


Energy-saving features and standby power

Some power strips have energy-saving features, which switch off the strip if appliances go into standby mode. Using a sensor circuit, they detect if the level of power through the socket is in standby mode (less than 30 watts), and if so they will turn off that socket. This reduces the consumption of
standby power Standby power, also called vampire power, vampire draw, phantom load, ghost load or leaking electricity ("phantom load" and " leaking electricity" are defined technical terms with other meanings, adopted for this different purpose), refers to ...
used by computer peripherals and other equipment when not in use, saving money and energy Some more-sophisticated power strips have a master and slave socket arrangement, and when the "master" socket detects standby mode in the attached appliance's current it turns off the whole strip. However, there can be problems detecting standby power in appliances that use more power in standby mode (such as plasma televisions) as they will always appear to the power strip to be switched on. When using a master–slave power strip, one way to avoid such problems is to plug an appliance with a lower standby wattage (such as a DVD player) into the master socket, using it as the master control instead. A different power strip design intended to save energy uses a passive infrared (PIR) or ultrasonic sound detector to determine if a person is nearby. If the sensors don't detect any motion for a preset period of time, the strip shuts off several outlets, while leaving one outlet on for devices that should not be powered off. These so-called "smart power strips" are intended to be installed in offices, to shut down equipment when the office is unoccupied. It is recommended that appliances that need a controlled
shutdown Shutdown or shut down may refer to: * Government shutdowns in the United States * Shutdown (computing) * Shutdown (economics) * Shutdown (nuclear reactor) Arts and entertainment Music * "Shut Down" (The Beach Boys song), 1963 * ''Shut Down Volu ...
sequence (such as many ink-jet printers) ''not'' be plugged into a slave socket on such a strip as it can damage them if they are switched off incorrectly (for example the inkjet printer may not have capped the print head in time, and consequently the ink will dry and clog the print head.) Within Europe, power strips with energy-saving features are within the scope of the Low Voltage Directive 2006/95/EC and the EMC Directive 2004/108/EC and require a
CE mark On commercial products, the letters CE (as the logo ) mean that the manufacturer or importer affirms the good's conformity with European health, safety, and environmental protection standards. It is not a quality indicator or a certificat ...
.


Socket arrangement

In some countries where multiple socket types are in use, a single power strip can have two or more kinds of sockets. Socket arrangement varies considerably, but for physical access reasons there are rarely more than two rows. In Europe, power strips without surge suppression are normally single row, but models with surge suppression are supplied both in single and double row configurations. If sockets on a power strip are grouped closely together, a
cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
with a large "
wall wart An AC adapter or AC/DC adapter is a type of external power supply, often enclosed in a case similar to an AC plug. Other common names include wall wart, power brick, wall charger, and power adapter. Adapters for battery-powered equipment may ...
"
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
at its end may cover up multiple sockets. Various designs address this problem, some by simply increasing the spacing between outlets. Other designs include receptacles which rotate in their housing, or multiple short receptacle cords feeding from a central hub. A simple DIY method for adapting problematic power strips arrangements to large "wall warts" is to use a three-way socket adapter to extend the socket above its neighbors, providing the required clearance. The
PowerCube The PowerCube is a multiple electrical socket adaptor manufactured by the Allocacoc Corporation in Shanghai, China. Unlike a conventional power strip, the device is arranged like a cube, which can solve the problem of multiple AC adapters fighting ...
adapter is arranged as a cube, meaning the adapters do not fight for space next to each other.


Surge protection and filtering

Many power strips have built-in
surge protector A 'surge protector'' (or spike suppressor, surge suppressor, surge diverter, surge protection device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices from voltage spikes in alt ...
s or EMI/RFI filters: these are sometimes described as surge suppressors or electrical line conditioners. Some also provide surge suppression for phone lines, TV cable coax, or network cable. Unprotected power strips are often mistakenly called "surge suppressors" or "surge protectors" even though they may have ''no ability to suppress surges''. Surge suppression is usually provided by one or more metal-oxide
varistor A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non- ohmic current–voltage characteristic that is similar to that ...
s (MOVs), which are inexpensive two-terminal
semiconductor A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
s. These act as very high speed switches, momentarily limiting the peak
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
across their terminals. By design, MOV surge limiters are selected to trigger at a voltage somewhat above the local mains supply voltage, so that they do not clip normal voltage peaks, but clip abnormal higher voltages. In the US, this is (nominally) 120 VAC. It should be borne in mind that this voltage specification is RMS, not peak, and also that it is only a nominal (approximate) value. Mains electrical power circuits are generally grounded (earthed), so there will be a live (hot) wire, a neutral wire, and a ground wire. Low-cost power strips often come with only one MOV mounted between the live and neutral wires. More complete (and desirable) power strips will have three MOVs, connected between each possible pair of wires. Since MOVs degrade somewhat each time they are triggered, power strips using them have a limited, and unpredictable, protective life. Some power strips have "protection status" lights which are designed to turn off if protective MOVs connected to the live wire have failed, but such simple circuits cannot detect all failure modes (such as failure of a MOV connected between neutral and ground). The surge-induced triggering of MOVs can cause damage to an upstream device, such as an
uninterruptible power supply An uninterruptible power supply or uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. A UPS differs from an auxiliary or emergency power system ...
(UPS), which typically sees an overload condition while the surge is being suppressed. Therefore, it is recommended not to connect a surge-protected power strip to a UPS, but instead to rely solely on surge protection provided by the UPS itself. More-elaborate power strips may use inductor-capacitor networks to achieve a similar effect of protecting equipment from high voltage spikes on the mains circuit. These more-expensive arrangements are much less prone to silent degradation than MOVs, and often have monitoring lights that indicate whether the protective circuitry is still connected. In the European Union, power strips with surge suppression circuits can demonstrate compliance with the (LVD) Low Voltage Directive 2006/95/EC by complying with the requirements of EN 61643-11:2002+A1. The standard covers both the performance of the surge suppression circuit and their safety. Likewise, power strips with telecoms surge suppression circuits can demonstrate compliance with the LVD by complying with the requirements of EN 61643-21:2001.


Daisy chaining and surge protection

Connecting MOV-protected power strips in a "daisy chain" (in a series, with each power strip plugged into a previous one in the chain) does not necessarily increase the protection they provide. Connecting them in this manner effectively connects their surge protection components in parallel, in theory spreading any potential surge across each surge protector. However, due to manufacturing variations between the MOVs, the surge energy will not be spread evenly, and will typically go through the one that triggers first. Daisy chaining of power strips (known in building and electric codes as multi-plug adapters or relocatable power taps), whether surge protected or not, is specifically against most codes. As an example, the International Code Council's ''International Fire Code 2009 Edition'' in 605.4.2 states, "Relocatable power taps shall be directly connected to permanently installed receptacles."


Overload protection

Where the current rating of the socket outlet, plug and lead of the power strip is equal to the rating of the circuit breaker supplying the circuit concerned, additional overload protection for the power strip is unnecessary, since the existing circuit breaker will provide the required protection. However, where the rating of a socket outlet (and, hence, the plug and lead of the power strip) is less than the rating of the circuit breaker supplying the circuit concerned, overload protection for the power strip and its supply cable is necessary. In the UK, standard BS 1363 plugs and sockets are rated at 13 A but are provided on circuits protected by circuit breakers of up to 32 A. However, UK
Consumer Protection Consumer protection is the practice of safeguarding buyers of goods and services, and the public, against unfair practices in the marketplace. Consumer protection measures are often established by law. Such laws are intended to prevent business ...
legislation requires that plug-in domestic electrical goods must be provided with plugs to BS 1363, which include a fuse rated at not more than 13 A. Hence, in the UK and in other countries using BS 1363 plugs, this fused plug provides overload protection for any power strip. The fuse must be replaced if the power strip is overloaded, causing the fuse to operate. In Australia and New Zealand the rating for a standard socket outlet is 10 Amperes but these outlets are provided on circuits usually protected by circuit breakers of 16 or 20 A capacity. Also, it is possible to insert an Australian/NZ 10 A plug into socket outlets rated at up to 32 A. Hence, all power strips sold in Australia and New Zealand with three or more 10A socket outlets are required to have overload protection so that if the total current drawn exceeds 10 A the inbuilt circuit breaker will operate and disconnect ''all'' connected devices. These power strips have a reset button for the circuit breaker, which is used to return the strip to service after an overload has caused it to trip.


Safety

Electrical overloading can be a problem with any sort of power distribution adapter. This is especially likely if multiple high-power appliances are used, such as those with heating elements, like room heaters or electric frying pans. Power strips may have a
circuit breaker A circuit breaker is an electrical safety device designed to protect an electrical circuit from damage caused by an overcurrent or short circuit. Its basic function is to interrupt current flow to protect equipment and to prevent the risk ...
integrated to prevent overload. In the UK, power strips are required to be protected by the fuse in the
BS 1363 Plugs and sockets for electrical appliances not hardwired to mains electricity originated in the United Kingdom in the 1870s and were initially two-pin designs. These were usually sold as a mating pair, but gradually de facto and then offici ...
plug. Some also feature a 13A BS1362 fuse in the socket end. Power strips are generally considered a safer alternative to “double adapters”, “two-way plugs”, “three-way plugs”, or “cube taps” which plug directly into the socket with no lead for multiple appliances. These low-cost adapters are generally not fused (although more modern ones in the UK and Ireland are). Therefore, in many cases the only protection against overload is the branch circuit fuse which may well have a rating higher than the adapter. The weight of the plugs pulling on the adapter (and often pulling it part way out of the socket) can also be a problem if adapters are stacked or if they are used with brick-style power supplies. Such adapters, while still available, have largely fallen out of use in some countries (although two- and three-way adapters are still common in the US, UK, and Ireland). When plugging a device into a power strip, a buildup of carbon or dust can cause sparking to occur. This generally doesn’t pose much of a risk in a non-explosive atmosphere, but explosive atmospheres (for example, near a gasoline refueling station or a solvent cleaning facility) require specialized explosion-proof sealed electrical equipment.


US regulations

*
Underwriters Laboratories The UL enterprise is a global safety science company headquartered in Northbrook, Illinois, composed of three organizations, UL Research Institutes, UL Standards & Engagement and UL Solutions. Established in 1894, the UL enterprise was founded a ...
standard 1363 contains requirements for ''relocatable power taps''. Included in the scope section of the standard is the statement: *
National Electrical Code The National Electrical Code (NEC), or NFPA 70, is a regionally adoptable standard for the safe installation of electrical wiring and equipment in the United States. It is part of the National Fire Code series published by the National Fire Prote ...
recognizes power strip as Multioutlet Assembly in Article 380.


EU and UK regulations

In Europe, plugs and sockets without additional control or surge protection circuits are outside the scope of the Low Voltage Directive 2006/95/EC and controlled by National regulations, and therefore must not be CE marked. In the UK the legal requirements for plugs and sockets are listed in Statutory Instrument 1994 No. 1768, The Plugs and Sockets etc. (Safety) Regulations 1994. This regulation lists the requirements for all domestic plugs and sockets; including socket outlet units (power strips), see Electrical Equipment - Requirements for Plugs & Sockets etc. - Guidance notes on the UK Plugs & Sockets etc. (Safety) Regulations 1994 (S.I. 1994/1768). The regulation requires all socket outlet units to comply with the requirements of BS 1363-2 Specification for 13A switched and unswitched socket-outlets and with the requirements of BS 5733 Specification for General requirements for electrical accessories. Sockets and socket outlets do not require independent approval under the regulations. Any plug fitted to the socket outlet unit must comply with the requirements of BS 1363-1 Specification for rewirable and non-rewirable 13A fused plugs. Plugs must also be independently approved and marked in accordance with the requirements of the regulation. If a socket outlet unit contains additional control circuits or surge protection circuits they will fall within the scope of the Low Voltage Directive 2006/95/EC and must be CE marked. Socket outlet units with control circuits also fall within the scope of the EMC Directive 2004/108/EC.


History

Outlet multipliers with the same purpose as power strips go back at least to the early 20s. However, these were usually not in a long "strip" like in modern devices. Examples of power strips exist in the U.S. patent system dating back as far as 1929, starting with the creation of Carl M. Peterson's "Table Tap". Another early example was created by Allied Electric Products in 1950. Perhaps the first modern designs for the power strip were created by the U.S. firm Fedtro, which filed two patents in 1970 for designs that were close to designs used in the modern day. One early iteration, called a "power board", was invented in 1972 by Australian electrical engineer Peter Talbot working under Frank Bannigan, Managing Director of Australian company Kambrook. The product was hugely successful, however, it was not patented and market share was eventually lost to other manufacturers."Powerful patents"
17 Sep 2012, IP Australia.


See also

*
AC power plugs and sockets AC power plugs and sockets connect electric equipment to the alternating current (AC) mains electricity power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and current rating, shape, si ...
*
Extension cord An extension cord (US), power extender, drop cord, or extension lead (UK) is a length of flexible electrical power cable (flex) with a AC power plugs and sockets, plug on one end and one or more sockets on the other end (usually of the same type ...
*
Power cord 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 t ...
*
Power distribution unit A power distribution unit (PDU) is a device fitted with multiple outputs designed to distribute electric power, especially to racks of computers and networking equipment located within a data center. Data centers face challenges in power protec ...
* Remote power boot switch *
Standby power Standby power, also called vampire power, vampire draw, phantom load, ghost load or leaking electricity ("phantom load" and " leaking electricity" are defined technical terms with other meanings, adopted for this different purpose), refers to ...


Notes


References

{{DEFAULTSORT:Power Strip Mains power connectors Australian inventions energy conservation fr:Multi-prise