A residual current device ( RCD ), or current-circuit breaker ( RCCB ), is a direct device cut off electrical circuits to prevent serious harm from continuous electrical shock. Injuries may still occur in some cases, for example if a human falls after receiving a surprise.
Also Known As:
- United States and Canada: this device is better known as disturbance of ground disturbance circuit ( GFCI ), land interrupter ( GFI ) or the current leakage interrupter tool ( ALCI ).
- English: this is better known by their initials RCD , and the combined RCD MCB (miniature circuit breaker) is known as RCBO ( circuit breaker current with overcurrent protection ) - Australia: they are best known singly as a Safety Switch otherwise known as RCD .
Earth leakage circuit breakers (ELCBs) can be residual current devices, although long-voltage voltage-breaker circuit breakers are available.
The power cable device is designed to quickly and automatically disconnect the circuit when it detects that an electric current is out of balance between the energy (s) conductor (line) and the return (neutral) conductor. Under normal circumstances, these two cables are expected to carry the appropriate current, and any difference may indicate a short circuit or other electrical anomaly that exists, such as a leak. Leaks can indicate a shock hazard (or shock in progress) which is a potential danger for a person. Leakage current may result in danger or death from electric shock, especially if the electric current leaks through the human body. A current of about 30 mA (0.030 amperes) is potentially enough to cause cardiac arrest or serious harm if it persists for more than a fraction of a second. The RCD is designed to disconnect wires fast enough to prevent serious injury from such shocks, commonly described as "tripped" RCDs.
RCD does not provide protection against unpredictable or very high currents (called spikes or spikes) when the current is in ordinary cable in circuit , therefore it can not replace the fuse or protect against overheating or risk of fire due to excess current (overloaded) or short circuit if error does not cause leakage current. Therefore, the RCD is often used or integrated as a single product together with some kind of circuit breaker, such as a fuse or miniature circuit breaker (MCB), which adds protection in case of overcurrent in the circuit (RCD produced with more current protection called RCBO). The RCD also can not detect situations where humans accidentally touch both conductors at the same time, because currents through expected devices, unexpected routes, or humans, can not be distinguished if the current returns through the expected conductor .
RCD is usually a device that can be tested and reset. Generally they include a button which, when pressed, safely creates a small leakage condition, and a switch that reconnects the conductor when the error condition has been cleared. Depending on the design, some RCDs release both the energy-driven conductor and return to a fault, while others simply disconnect the energy conductor and depend on the conductor returning to the ground potential (earth). The first is commonly known as the "double pole" design; the latter as a "single pole" design. If the error has left the wire back "floating" or not on the expected ground potential for any reason, then a single pole RCD will leave this conductor still connected to the circuit when it detects an error.
Video Residual-current device
Goals and operations
RCD is designed to break the circuit if there is a leakage current. By detecting small leakage currents (usually 5-30 mA) and breaking fast enough (& lt; 30 ms), they can prevent power flow. They are an essential part of automatic supply termination (ADS), that is to shut down when errors develop, rather than rely on human intervention, one of the essential principles of modern electrical practice.
To prevent power outages, the RCD must operate within 25-40 milliseconds with a leakage current (through a person) greater than 30 mA, before an electric shock can propel the heart into ventricular fibrillation, the most common cause of death through electric shock. In contrast, conventional circuit breakers or fuses only disconnect the circuit when excessive total (which may be thousands of leaks generated by the RCD). Small leakage currents, such as through a person, can be a very serious mistake, but it probably will not increase enough current to fuse or circuit breakers to break the circuit, and certainly not fast enough to save lives.
The RCD operates by measuring the current balance between two conductors using a differential current transformer. It measures the difference between the current flowing through the direct conductor and the return through the neutral conductor. If this does not amount to zero, there is a leakage current to another (to earth/ground or to another circuit), and the device will open the contact. Operation does not require an interruption current to return through the earth cable in the installation; the journey will operate properly if the return path is via a plumbing, contact with the ground or any other current path. The automatic disconnection and shock protection measure is therefore still provided even if the wiring on earth is damaged or incomplete.
Residual detection-currently completes over-current detection. Residual current detection can not provide protection for overload currents or short circuits, except for special cases of short circuit from life to ground (not life to neutral).
For RCDs used with three phase power, the three live and neutral conductors (if installed) must pass through the current transformer.
Maps Residual-current device
Apps
Circuit interrupter circuit breakers (GFCI breakers in the United States and Canada) and overloaded residual solvers (RCBO in Europe) are devices that combine the function of residual current devices with circuit breakers. They detect supply imbalances and weigh on currents.
In Europe, RCDs can be loaded on the same DIN rail as MCB, but busbar arrangements in consumer units and distribution boards can make it awkward to use them in this way. If it is desired to protect individual circuits, the RCBO (residual current circuit breaker with overcurrent protection) can be used. It combines RCD and miniature circuit breakers in one device.
Electrical plugs with incorporated RCDs are sometimes mounted on equipment that may be perceived as causing certain safety hazards, such as long extension connections, which may be used outdoors, or gardening equipment or hair dryers, which can be used near a bathtub or washbasin. Sometimes an in-line RCD can be used to serve functions similar to one in a plug. By placing the RCD on an extension connection, protection is provided at any outlet that is used even if the building has old cables, such as buttons and tubes, or cables that do not contain a grounding conductor.
In North America, GFI containers can be used in cases where there are no grounding conductors, but they should be labeled as "ungrounded". An unmade GFI container will stumble using the built-in "test" button, but will not trip over using the GFI test plug, because the plug tests shorten the small current from the line to the ground that does not exist.
The power socket with the included RCD becomes common.
General design
The diagram illustrates the internal mechanism of residual-time devices (RCD). The device is designed to be connected directly in the utility power cord. It is rated to carry a maximum current of 13 A and is designed for travel on leakage current of 30 mA. This is an active RCD; ie, electrically coupling and therefore a power failure, a useful feature for equipment that can be harmful to unexpected re-energies. Some early RCDs are fully electromechanical and depend on a mechanism that is moved smoothly above the center which is driven directly from the current transformer. Because it is difficult to be made in accordance with the required accuracy and susceptible to sensitivity that deviates from the wear and tear of dry, electronically-strengthened pivot and lubricant with a stronger solenoid part as now dominant.
The incoming supply and the neutral conductors are connected to the terminal at (1), and the outgoing conductor is connected to the terminal at (2). The earth conductor (not shown) is connected through from supply to uninterrupted load. When the reset button (3) is pressed, the contacts ((4) and the other, hidden behind (5)) close, allowing the current to pass. Solenoid (5) makes the contact closed when the reset button is released.
The sense coil (6) is a differential current transformer that surrounds (but is not electrically connected with) a live and neutral conductor. In normal operation, all living current downflow returns the neutral conductor. The currents in both conductors are the same and opposite and cancel each other.
Any error on earth (eg caused by someone touching a live component in an attached device) causes some currents to take a different turning point, which means that there is an imbalance in the current in two conductors (single-phase case), or, more general, nonzero quantities of currents from between the various conductors (eg, three phase conductors and one neutral conductor).
This difference causes the current in the sense coil 6, which is taken by the sense circuit 7. The sense circuit then removes power from the solenoid (5), and contact (4) is forced apart by the spring, cutting off the power supply to the appliance.
This device is designed in such a way that the current is disrupted in milliseconds, greatly reducing the likelihood of a dangerous electric shock being received.
The test button (8) allows correct device operation to be verified by passing a small current through the orange test wire (9). It simulates errors by creating an imbalance in the sensory coils. If the RCD does not trip over when the button is pressed, then the device must be replaced.
RCD with additional overcurrent protection circuit (RCBO or GFCI breaker)
Overcurrent and overcurrent protection can be incorporated in a single device to be attached to the service panel; the device is known as a GFCI breaker (basic circuit breaker) in the United States and Canada, and as RCBO (circuit breaker with overload protection) in Europe. In the US, GFCI breakers are more expensive than GFCI outlets.
In addition to requiring line and neutral inputs and outputs (or, 3 full phases), many GFCI/RCBO devices require functional earth connections (FE). This serves to provide EMC immunity and to operate the device reliably if the input-neutral connection is lost but remains and the earth remains.
For space reasons, many devices, especially in the DIN rail format, use fly leads rather than screw terminals, especially for neutral inputs and FE connections. In addition, due to the small form factor, the output cables of some models (Eaton/MEM) are used to form the primary windings of the RCD portion, and the outgoing circuit cables must be led through a special dimensionally tunnel terminal with the current transformer of the surrounding parts. This can lead to incorrect trip results when testing with the meter probe from the screw head of the terminal, not from the last circuit circuit.
Having one other meal RCD is generally not necessary, provided they have been transferred properly. One exception is the case of the TT grounding system, where the impedance of the earth loop may be high, meaning that the soil interference may not cause sufficient current for the regular trip of the circuit breaker or fuse. In this case a special trip of 100 mA (or larger) delayed RCD is currently installed, which includes all installations, and then a more sensitive RCD should be installed downstream for sockets and other circuits considered high risk.
RCD with additional arc damage protection circuit
In addition to Ground Fault Circuit Interrupters (GFCIs), Arc-fault interference interference devices (AFCI) are also important as they offer additional protection from potentially harmful arc disturbances resulting from damage to branch circuit cables as well as extensions to branches such as equipment and cable sets. By detecting harmful arc disturbance and responding with power failures, AFCI helps reduce the possibility of home electrical systems becoming the source of ignition. AFCI/GFCI Dual Function devices offer electric fire prevention and shock prevention in a single device that makes it a solution for many rooms in the home, especially when replacing existing standard containers or ungrounded containers.
General features and variations
Differences in disconnection actions
The main difference is in the way in which the RCD will act to disconnect power to a circuit or device.
Two different nomenclature are being used to identify what is essentially the main feature ie. either 'Active' or 'Passive', and 'Latched' or 'non-Latching'.
All RCDs have a latching feature. The bolt becomes set when the device is armed - usually by moving the switch to the active position, or pressing the reset button. Once armed, the device allows power to flow until several electrical events occur that cause the latch to become unset. Such triggers are usually intended to detect serious electrical irregularities, but un-latching can also occur by termination of power; Such power cuts are not considered irregular events, and include events such as users who decide on the intentional or inadvertent power, or temporary power failure associated with the service provider.
The 'Active' RCD operates to release itself when irregular electrical events occur, and that includes any simple power cuts caused by any means; there is no automatic re-connection operation that follows any termination causing RCD triggered; power to the circuit or device will remain interrupted until RCD has been manually reset by the user.
The 'Passive' RCD operates to disengage itself only when electrical irregularity appears to be a serious electrical fault. However, unless the power has been disconnected by the RCD un-latching itself (or by the user manually triggering the device), the RCD will remain locked during the period when the power is disconnected, and remains locked and ready to continue using. in its armed mode as soon as the power supply is restored.
RCDs that are installed as fixed devices in consumer power distribution units are almost always from passive variations, so household appliances such as refrigerators and freezers will return to their regular operating mode as soon as the power supply resumes normal operation.
Most portable RCD types are of various active, and all trigger events will cause them un-latch-specific settings to avoid the resumption of power when the power supply that was previously disconnected by the RCD itself is restored. This type of action is highly desirable with tools such as electrical appliances and garden machines that can be dangerous if they are reactivated without personal supervision. This type of portable RCD is generally an active type of plug-top design intended to be attached to an individual device, or as a plug-in unit to fit between the appliance plug and the outlet, or built into an extension cord.
However, it is possible to obtain some kind of passive adhesive device for permanent installation directly to the utility power cord, or to be inserted into the power line of the selected equipment - sometimes manifested in the form of a plug over a manual cable such as an english rectangle of various blades. It is assumed that a passive RCD will be paired only and directly to the appropriate equipment.
The subsequent variation of fitting to RCD is by incorporation into a wall outlet, where a choice of active or passive fittings is available - assuming that the user will be aware of the nature of the equipment to be connected and will limit the use of such wall sockets.
Passive RCDs tend to be made within 30 milliseconds of 40 milliseconds (and higher in CPDUs for special purposes). Active varieties are often available in lower travel rankings (as low as 10 ma), and more options from lower ratings may be available; their travel time is often 30 milliseconds. (All currents stated here are 250 volts). Lower rankings in RCDs are more prone to cause stumbling disorders for no apparent reason.
Number of poles and polar terminology
The number of poles indicates the number of impaired conductors when a fault condition occurs. RCDs are used on single-phase AC supply (two current paths), such as domestic power, usually one or two pole designs, also known as single and double poles. A single pole RCD only interferes with an energetic conductor, while a double pole RCD interferes with both the energy and return conductor. (In a single pole RCD, the return conductor is usually anticipated to be in the ground potential at all times and hence its own safe, but see limitations below).
RCDs with three or more poles may be used on a three-phase AC supply (three current lines) or to break the earth carrier as well, with a four-pole RCD used to disrupt the neutral three-phase supply. Specially designed RCDs can also be used with AC and DC power distribution systems.
The following terms are sometimes used to describe the way in which conductors are connected and disconnected by the RCD:
-
- One pole/SP/one pole - RCD will only disconnect the energized cable.
- Two poles/DP/two poles - The RCD disconnects the powered and backed cables.
- 1 N and 1P N - non-standard terms used in the RCBO context, sometimes used differently by different manufacturers. Usually these terms may indicate that the (neutral) return conductor is the only insulating pylon, with no protective elements (unprotected but neutral switches), or that the RCBO provides and connectors to return (neutral) conductors but these paths remain undisturbed when an error occurs (sometimes known as "solid neutral" ), or that both conductors are disconnected for some errors (such as RCD detect leaks) but only one conductor is disconnected due to another error (such as overload).
Sensitivity
The RCD sensitivity is expressed as the residual operating current of the identifier, recorded I ? N . The selected value has been determined by IEC, so it is possible to divide RCD into three groups according to I value? N them:
- high sensitivity ( HS ): 5 ** - 10 - 30 mA (for direct contact protection/injury protection),
- moderate sensitivity ( MS ): 100 - 300 - 500 - 1000 mA (for fire protection),
- low sensitivity ( LS ): 3 - 10 - 30 A (usually for machine protection).
Typical 5 mA sensitivity for GFCI outlets.
Break time (response rate)
There are two sets of devices. G (common use) instant The RCD does not have any deliberate deliberate delays. They should not travel at half of their current nominal value, but must travel within 200 milliseconds for the rated current, and within 40 milliseconds at five times the measured current. S (selective) or T (time-delayed) The RCD has a short delay time. They are usually used at the beginning of the installation for fire protection to differentiate with the G device on the load, and on the circuit containing the current surge suppressor. They do not have to travel with half of the rated flow. They provide at least 130 milliseconds of delay tripping on the rated current, 60 milliseconds twice, and 50 milliseconds at five times. Maximum rest time is 500 ms at rated current, 200 ms twice, and 150 ms five times.
Programmed error earth relay is available to enable coordinated installation to minimize power outage. For example a power distribution system might have 300 mA, a 300 md device at the building service entrance, feeding some 100 mA S types on each sub-board, and 30 mA G type for each last series. In this way, device failure to detect errors will eventually be removed by higher level devices, with the cost of disturbing more circuits.
Type, or mode (type of leakage current problem detected)
IEC Standard 60755 ( General requirements for residual current operated protective devices ) defines three types of RCD depending on the waveform and the frequency of fault current. Type AC RCD trips on sinusoidal residual currents. Type A The RCD also responds to the pulsed or continuous direct current of the polarity. Type B The RCD also responds to a higher frequency current, or for a combination of alternating and direct current that can be found from a single phase or phase circuit.
Increase the current resistance
The surge current refers to the RCD peak current designed to withstand using a specified characteristic impulse test. IEC 61008 and IEC 61009 standards require that RCD withstand 200 ampere "ring wave" impulses. Standards also require that RCDs be classified as "selective" to withstand impulse surge currents of 3000 amps from certain waveforms.
Test the correct operation
RCD can be tested with installed test buttons to confirm functionality on a regular basis. The RCD may not operate properly if the cable is not correct, so it is generally tested by the installer to verify the correct operation. The use of a solenoid voltmeter from life to earth provides an external path and can test the cable to the RCD. Such tests can be performed on the installation of the device and at any "downstream" outlet.
Limitations
The residual circuit breaker can not eliminate all risks of electric shock or fire. Specifically, the RCD alone will not detect overload conditions, short-circuit phase-to-neutral or phase-to-phase short circuits (see three phase power). Overcurrent protection (fuse or circuit breaker) shall be provided. Circuit breakers that incorporate RCD functions with overcurrent protection respond to both types of errors. This is known as RCBO and is available in 2-, 3- and 4-pole configurations. RCBOs usually have separate circuits to detect current imbalances and for overcurrent but using common interrupt mechanisms.
RCD helps protect against electric shock when current flows through a person from phase (life/line/heat) to the earth. It can not protect against electric shock when current flows through a person from phase to neutral or from phase to phase, for example where the fingers touch the live and neutral contacts in light mounting; the device can not distinguish between the flow of current through the desired load from the flow through a person, although the RCD may still stumble if the person is in contact with the ground (earth), as some currents may still pass through the finger and body of the person to the earth..
All installations on a single RCD, common in older installations in the UK, are susceptible to travel "disruptions" that can cause secondary security problems with loss of lighting and liquefaction of food. Often the journey is caused by insulation that worsens the heating element, such as a water heater and an element or a cooker ring. Although regarded as a nuisance, the fault is with a worsening element and not an RCD: replacing the offending element will solve the problem, but replacing the RCD will not.
In case of RCD requiring power supply, hazardous conditions may arise if the neutral cable is damaged or shut off on the RCD supply side, while the corresponding live wires remain uninterrupted. The tripping circuit requires power to work and does not trip over when the power supply fails. The connected equipment will not work without being neutral, but the RCD can not protect people from contact with electrically grounded wires. For this reason circuit breakers must be installed in a way that ensures that neutral cables can not be switched off unless the live wire is also turned off at the same time. Where there is a requirement to turn off the neutral cable, a two-pole breaker (or four poles for 3-phase) should be used. To provide protection with impaired neutrals, some RCD and RCBOs are equipped with additional connection cables that must be connected to the earth busbar of the distribution board. This allows the device to detect lost neutral supplies, cause the device to travel, or provide an alternative supply path for tripping circuits, allowing it to continue functioning normally without a neutral supply.
Related to this, a single pole RCD/RCBO only interferes with a powerful conductor, while multiple polar devices interfere with both the energy-driven conductor and the return. Usually this is a standard and safe practice, because the return conductor remains on the basic potential. However, due to its design, a single polar RCD will not isolate or disconnect all relevant cables under certain circumstances, for example where the return conductor is not retained, as expected, on the ground potential, or where a leakage current occurs between the return and the earth conductor. In this case, a double-pole RCD will provide protection, since the return conductor will also be disconnected.
History and nomenclature
The world's first high-sensitive leakage protection system (ie a system capable of protecting people from the danger of direct contact between living and earth conductors), is a harmonic second-harmonic core-balance system, known as magamp, developed in South Africa by Henri Rubin. The dangers of electricity are very apprehensive in the South African gold mine, and Rubin, an engineer at CJ Fuchs Electrical Industries Alberton Johannesburg, initially developed a cold cathode system in 1955 that operates at 525 V and has a sensitivity tripping 250 mA. Prior to this, the Earth's core balance leakage protection system operated on a sensitivity of about 10 A.
Cool cathode systems are installed in a number of gold mines and work reliably. However, Rubin began to work on a completely new system with a greatly increased sensitivity, and by early 1956, it had produced a second-type harmonic-type magnetic-type nuclear amplifier (South African Patent No. 2268/56 and Australian Patent No. 218360). The prototype magamp is rated at 220 V, 60 A and has an internal adjustable sensitivity adjusted from 12.5 to 17.5 mA. The very fast tripping time is achieved through the new design, and this is combined with high sensitivity in both the safe moment envelopes for ventricular fibrillation determined by Charles Dalziel of the University of California, Berkeley, USA, who estimates the dangers of electric shock in humans. This system, with its associated circuit breakers, includes overcurrent protection and short circuit. In addition, the original prototype is able to travel at lower sensitivity in the presence of impaired neutrals, thus protecting against important causes of electric fires.
Following the unintentional accident of a woman in a domestic accident in the gold mining village of Stilfontein near Johannesburg, several hundred F.W.J. 20 mA magamp earth leakage protection units were installed in the mining village houses during 1957 and 1958. F.W.J. The Electrical Industry, later renamed FW Electrical Industries, continues to produce 20 mA single phase and three phase magamp units.
As he worked in magamp, Rubin also considered using transistors in this application, but concluded that the initial available transistors were too unreliable. However, with the advent of better transistors, the companies where he works and other companies then produce versions of earth leakage transistor protection.
In 1961, Dalziel, working with Rucker Manufacturing Co., developed a transistorized device for ground leakage protection known as Ground Fault Circuit Interrupter (GFCI), sometimes abbreviated to Ground Fault Interrupter (GFI). This name for high sensitivity earth leakage protection is still commonly used in the US.
In the early 1970s most of the North American GFCI devices were circuit type breakers. GFCI built into an outlet socket became a common start in the 1980s. The type of circuit breaker, fitted to the distribution panel, experienced accidental travel is mainly due to poor or inconsistent insulation of cables. The wrong journey often occurs when the problem of isolation is compounded by the length of the long circuit. So much current leaks along the isolation of the conductor so that the breaker may experience a slight increase in current imbalance. Migration to outlet-based protection in North American installations reduces accidental travel and provides clear verification that the wet areas are under the required protection of electrical codes. European installations continue to use primarily RCD mounted on distribution boards, which provide protection in case of damage to fixed cables; In Europe, Socket-based RCDs are used primarily for retro installations.
Rules and adoptions
The rules differ widely from country to country. In most countries, not all home circuits are protected by RCD. If a single RCD is installed for all electrical installations, any error can trim all power to a place.
Australia
In Australia, residual current devices have been required on electric circuits since 1991 and on light circuits since 2000. Minimum two RCDs are required per domestic installation. All sockets and lamp circuits must be distributed through the RCD circuit. Maximum of three sub-circuits only, can be connected to one RCD.
Austria
Austria set up residual current device in ÃÆ'-VE E8001-1/A1: 2013-11-01 norm (latest revision). This has been requested in private homes since 1980. The maximum activation time should not exceed 0.4 seconds. It needs to be installed in all circuits with an electrical outlet with a maximum leakage current of 30 mA and a rated rated maximum of 16 A.
Additional requirements are placed on circuits in wet areas, construction sites and commercial buildings.
Belgium
The Belgium domestic installation should be equipped with a 300 mA residual current device that protects all circuits. In addition, at least one 30 mA remaining current device is required that protects all circuits in "wet rooms" (eg bathrooms, kitchens) as well as circuits that power certain "wet" appliances (washing machines, dryers, dishwashers). Under-floor electrical heating is required to be protected by a 100 mA RCD. This RCD should be type A.
Brazil
Because NBR 5410 (1997) the remaining devices and grounding are currently required for new construction or repairs in wet areas, outdoor areas, interior outlets used for external equipment, or in areas that allow water such as bathrooms and kitchens.
Denmark
Denmark requires 30 mA RCD on all circuits rated less than 20 A (circuits in larger ratings are mostly used for distribution). RCD became mandatory in 1975 for new buildings, and then for all buildings in 2008.
German
Since May 1, 1984, RCD is compulsory for all rooms with bath or shower. Since June 2007 Germany requires the use of RCDs with travel flows of not more than 30 mA on jackets rated up to 32 A for general use. (DIN VDE 0100-410 No. 411.3.3).
India
According to Rule 36 of the Electricity Regulations 1994
a) For public entertainment venues, protection against earth leakage shall be provided by the residual current device of sensitivity not exceeding 10 mA.
b) For places where floors tend to be wet or where walls or enclosures have low electrical resistance, protection against leakage of earth currents should be provided by residual current devices sensitivity not exceeding 10 mA.
c) For installation in which equipment, apparatus or handheld device may be used, the protection against earth leakage shall be provided by the residual current device of sensitivity not exceeding 30 mA.
(d) For installations other than installations in (a), (b) and (c), the protection against earth leakage shall be provided by the residual current device sensitivity not exceeding 100 mA.
Italy
Italian Law (n.45, 1990) regulates the RCD with no more than 30 mA of residual current (informally called "salvavita" - life saver, after the initial Bticino model, or differential circuit breaker for the mode of operation) for all domestic installations to protect all lines. The legislation has recently been updated to mandate at least two separate RCDs for separate domestic circuits. Magnetic and thermal protection has been required since 1968.
New Zealand
Starting January 2003, all new circuits coming from the switchboard supplying the lamp or power socket in the domestic building must have RCD protection. Housing facilities (such as boarding houses, hospitals, hotels and motels) will also need RCD protection for all new circuits coming from switchboards that provide sockets. This RCD is usually placed on the switchboard. They will provide protection for all power cords and equipment plugged into the new circuit.
North America
In North America containers located in places where there is an easy path to the ground - such as wet areas and rooms with open concrete floors - should be protected by GFCI. The US National Electrical Code has required devices in certain locations to be protected by GFCI since the 1960s. Beginning with subsea swimming pool lights (1968) the successive edition of the code has expanded the area where GFCI was requested to enter: construction site (1974), bathroom and outdoor area (1975), garage (1978), area near tub hot water or spa (1981), hotel bathroom (1984), kitchen container (1987), crawl room and unfinished basement (1990), near wet sink (1993), near sinks (2005) and in laundry room (2014).
GFCI is generally available as an integral part of a wall outlet or circuit breaker installed in the distribution panel. GFCI receptacles always have rectangular faces and receive what are called Decora face plates, and can be mixed with regular outlets or switches in multi-aisle boxes with standard cover plates. Both in Canada and in the United States, two larger cables, the old NEMA 1 container can be replaced with a NEMA 5 container protected by GFCI (integral to the container or with an appropriate circuit breaker) instead of rewiring the entire circuit with the grounding conductor. In such cases the container should be labeled "no soil equipment" and "GFCI protected"; GFCI manufacturers usually tag for appropriate installation descriptions.
GFCI is approved for protection against electric shock at 5 mA in 25 ms. GFCI devices that protect equipment (not people) are allowed to travel as high as 30 mA of current; this is known as Device Protector Tool (EPD) . RCDs with 500 mA high travel currents are sometimes placed in environments (such as computing centers) where lower thresholds carry unacceptable risk of accidental travel. This high current RCD serves for fire protection and equipment in place of protection against the risk of electric shock.
In the United States, the American Boat and Yacht Council require GFCI for outlets and Equipment Leakage Circuit Interrupters (ELCI) for the entire vessel. The difference is a GFCI trip at 5 mA of current while traveling ELCIs at 30 mA after up to 100 ms. Larger values ​​are intended to provide protection while minimizing journey travel.
Norwegian
In Norway, this has been mandatory in all new homes since 2002, and in all new sockets since 2006. This applies to sockets 32A and below. RCD should trigger after maxium 0.4 second for 230V circuit, or 0.2 second for 400V circuit.
South Africa
South Africa mandated the use of the Earth Leakage Device in residential environments (eg houses, flats, hotels, etc.) From October 1974, with enhanced regulations in 1975 and 1976. Devices had to be installed in new places and when repairs were made outside. Required protection for electrical outlets and lights, with the exception of emergency lighting that should not be disturbed. The standard device used in South Africa is indeed a hybrid of ELPD and RCCB.
Turkish
Turkey requires the use of RCDs with no more than 30 mA and 300 mA in all new homes since 2004. This rule was introduced in RG-16/06/2004-25494.
United Kingdom
The previous 16th edition of the IEE Electrical Wiring Regulations requires the use of RCDs for socket outlets that can be used by external equipment. The normal practice in a domestic installation is to use a single RCD to include all circuits that require RCD protection (usually sockets and showers) but to have some circuits (usually lighting) unprotected by RCD. This is to avoid the possibility of dangerous lighting loss if RCD trips. The protection settings for other circuits vary. To apply this setting it is common to install a consumer unit incorporating RCD in what is known as a separate load configuration, where one group of circuit breakers is supplied directly from the main switch (or RCD time delay in the case of TT earth) and a second group of circuits is provided via RCD. This arrangement has a recognized problem that the cumulative earth leakage current from the normal operation of many equipment can lead to counterfeit tripping of the RCD, and that the tripping of the RCD will disconnect power from all protected circuits.
The current edition (17th) of the regulations requires that all outlet sockets in most domestic installations have RCD protection, although there are exceptions. Cables buried in the wall must also be protected by RCD (again with some special exceptions). {See Amendment 17th Edition of Amendment 1 effective since January 2012} RCD protection provisions for existing circuits in bathrooms and showers reduce the requirement for additional supplements at those locations. Two RCDs can be used to close the installation, with upstairs and down lighting as well as power circuits spread across both RCDs. When one trips the RCD, power is maintained at least one lamp and electrical circuit. Other settings, such as the use of RCBO, can be used to comply with regulations. New requirements for RCDs do not affect most existing installations unless they are replaced, distribution boards change, new circuits are installed, or changes made like additional sockets or new wires grown on the wall.
The RCD used for shock protection shall be of 'direct' operation type (not time-delayed) and shall have a residual current sensitivity of not more than 30 mA.
If it can be shown that false tripping will cause a problem greater than the risk of electrical accidents that should prevent RCD (for example may be the supply for important plant processes, or life support equipment), RCD can be eliminated, providing the affected circuit clearly labeled and balance of risks considered, this may include the provision of alternative safety measures.
See also
- The isolation monitor
- Electric plugs and domestic AC sockets
References
External links
- GFCI Fact Sheet (Consumer Product Safety Commission)
- RCCB test according to IEC 61008/61009 (Current Current Device Testing)
- Why does the RCD stumble? - Explanation of cause of tripping disorder
Source of the article : Wikipedia
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