Residual-current device

Residual current circuit breaker (RCCB ), also colloquially ' RCD ', the most commonly used devices from the parent group of the " residual current protective devices " (RCD), as it is now generally referred to in the standards of the German-speaking area are. Residual current protective devices of any design prevent dangerous high fault currents to ground and thus contribute to the reduction of life-threatening electrical accidents in low voltage networks significantly.

Due to the influence of international standardization the abbreviation "RCD " for the English name Residual Current protective Device ( mutatis mutandis residual current protection device) is commonly used since 2008 in the German standards.

Residual current protective devices are generally preceded by the usual over-current protection devices and installed in addition to those in the low voltage switchboards. There is also the combination in the form of the RCBO, which combines the function of the residual current protective device and the circuit breaker in one device. Also RCD sockets are available for the fault current protection of individual outlets in existing installations.

In the earlier common abbreviation FI was "F" for the word error and "I" for the symbols of the electric current.

3.1 Germany
3.2 Austria
3.3 Switzerland

5.1 button for function test ( test button )
5.2 RCD test according to DIN VDE 0100-600 (as of 06-2008 )
5.3 RCD test type A ( Switzerland )

Basics

According to DIN VDE 0100-100, the safety of persons, domestic animals and property with regard to the danger and damage, make sure that arise from improper use of electrical equipment. This includes in particular dangers involved in contact with live parts may cause electrical systems. This protection can be achieved by the following measures:

Prevent a fault current through the body of a person or a farm animal flows
Limiting the fault current that flows through a body to a safe value
Limiting the fault current that flows through a body to a safe period of time

Residual current protective devices are aimed in addition to the measures from " protective earthing and protective bonding " (according to DIN VDE 0100-410 ) to measure the time- limiting. They protect against the persistence - not the creation - an impermissibly high touch current ( see also contact voltage ). They are an efficient means to avoid dangerous electrical accidents, particularly the ground fault over the body.

Another very important aspect for the use of residual current devices is fire protection. In fire protection engineering, an error output of more than 60 watts is classified as a possible causes of fire by prolonged duration of action. Under certain conditions, even to be expected at lower powers with fire. For fire safety reasons, therefore, protective equipment, reporting or monitoring devices with a rated residual current / Operating current ≤ 300 mA are recommended. Such guards for preventive fire protection typically have a delayed release and are also due to the high rated residual current not for personal protection.

In contrast, over-current protection devices serve as miniature circuit breakers or fuses, which are generally referred to as " backups ", mainly to protect equipment and installations, and therefore do not provide adequate protection against electric shock: " the fuse protects the cable, the fault current protective device the people."

Prerequisite for a reliable direct triggering of the fault current protection device at an unacceptably high fault current is a standardized interpretation of the customer's system, especially with regard to protective earthing and potential equalization. In simple errors a circuit through the protective conductor or the earth is formed by the earth contact of operational live -carrying conductor. The grid-side requirements are generally met with European Low Voltage networks ( with some exceptions such as in IT systems where fault current protection devices can only be used for the detection of multiple errors ) and by the respective distribution system operator (DSO ) guaranteed. In the sections of a TN -C system, in which the protective conductor ( PE conductor ) Neutral ( N conductor ) is at the same time ( and is referred to as a PEN conductor ), a residual current protective device only after the split into separate PE conductor and N conductor are used. After the splitting of the N conductor is passed over the residual current protection device. This splitting of the PEN conductor is usually in the service box, so this has no other effect on the normal house or apartment installation.

Principle of operation

The fault current protection switch disconnects when exceeding a certain differential current in house facilities and public buildings usually 30 mA, the monitored circuit at all poles, that is all head down to the protective conductor from the rest of the network.

Residual currents can occur when an (error) current flows through the human body or as a defective insulation. For this purpose, the fault current protection switch compares the height of the back with the back of the flowing stream. The signed sum of all the currents flowing through the earth leakage circuit breaker currents must be in an intact plant zero. In other words, the current to the consumer must be as large as the current which flows back from the load.

The comparison is made in a sum current transformer. It has two or more continuous wires (primary windings). They are guided so that their mutual induction effect of reversing the normal case, no magnetic flux is induced in the transformer core, and no secondary current flows. The converter "added" all that is to and flowing from the load currents with the correct sign. Flows from a vein some current to ground (fault current), the sum of currents flowing back and forth is no longer zero in the transducer. This results in a current in the secondary coil ( tripping coil ) result. The secondary current triggers a relay ( switch lock ) which switches off all poles of the line.

Limits of the protective effect

A residual current circuit breaker will not protect against electric shock if a person is on an insulating substrate standing both AC wires (L and N) touched since no leakage occurs. Likewise, no protection is provided if an unwanted current between multiple phases (L1, L2 or L3) flows in a three- phase AC mains. Touching, for example, at the junction box of an electric stove or an instantaneous water heater at the same time several conductors of three-phase current can only trigger a fault current protective device when a fault current to ground flows.

A residual current circuit breaker provides inherently no protection from the effects of head -circuit, overload and short circuit, these conclusions do not ground current ( ground fault) include. This calls for additional protective devices such as the various forms of overcurrent protective device, examples are fuses or circuit breakers, necessary. In special operating areas in addition to the fault current circuit breaker, the fault arc protection devices are used.

Structure of the summation current transformer

The summation current transformer consists of a toroidal core wound of crystalline or nanocrystalline soft magnetic tape. Ferrite cores are not suitable due to the too low permeability. In order to achieve the necessary power to trigger the residual current circuit breaker, toroidal cores are necessary with a certain size and mass, typical dimensions are outside diameter of about 25 mm, inner diameter about 15 mm, height 20 mm, typical weight 40 g

Types according to the type of the fault current

There are in total three main types of residual current devices, which depending on the nature of the fault current, they can detect, such as differentiated according to the adjacent diagram:

The use of type B is especially for inverters and frequency converters, which operate in the area of the intermediate circuit with rectifiers, is essential. Conventional RCD type A would be an earth fault behind the rectifier bridge and biased functional by the then existing DC residual current.

Combined types RCD / MCB and RCD socket

There are also combined with RCD circuit breakers ( CB ) (eg: 30 mA RCD and 13 A circuit breaker ) which are called RCBO. An RCBO with the number of poles 1P N typically has the same mounting width as a two-pole circuit breaker.

In order to protect individual sockets with RCD, RCD sockets are also ( SRCD ) available. They are used to increase the protection level and only submit a supplementary protection; they do not replace a conventional RCD according to DIN EN 61008-1 (VDE 0664-10 ) where this is required.

Characteristics

Commercially are ground fault circuit breaker in the type A for rated residual currents of IΔN = 10 mA, 30 mA, 100 mA, 300 mA, 500 mA and 1 A. The tolerance of differential current of a residual current circuit breaker is according to VDE at -50 %, which is supposed to guarantee that the rated tripping current is exceeded on any copy. In practice, the tripping RCDs commercial takes place at about 0.8 * IΔN.

For personal protection, a maximum operating current of 10 mA or 30 mA and for fire protection prescribed by a 300 mA. The maximum time for non-selective residual current circuit breaker is determined (up to 230 V at rated voltage 120 V ) for simple nominal fault current according to VDE standard DIN VDE 0100-410:2007 Table 41.1 to 400 ms in the TN system. Trigger at 5 times the rated fault current must be the fault current breaker under 40 ms.

Selectivity

The selective nature and operation of devices with line filters (higher leakage current at power up) -delayed types are available. The switch-off with a simple nominal fault current between 200 and 500 ms here. At 5 times the rated fault current they must trigger between 40 and 150 ms. Note that a residual-current circuit breaker, the height of the fault current is not limited; he switched only when it reaches the set maximum differential current height from the error stream. This means that until shutdown ( depending on the model, eg, 30 ms) can only flow from the mains or an overcurrent protective device limited high current.

Designations, disambiguation

In German standards, the following terms have been used in the past:

Residual current device (RCD ) for voltage-independent units (without auxiliary power source)
Residual current circuit breaker ( DI) for voltage- dependent devices (with auxiliary voltage source).

Commercially, there are also:

Operated circuit breaker is a marketing name and technically well defined.
Safety switch is a term that is used for earth leakage circuit breaker in supply lines and extensions, as well as in intermediate connectors and is otherwise not well defined. The BGI608 makes for such portable protective equipment requirements when used as a feed point for so-called small construction sites.

For residual current circuit breakers, which are combined with miniature circuit breakers, the following designations were used:

FI / LS- breaker if they were independent of mains voltage,
DI / MCB device, if they were dependent on mains voltage.

The distinction between voltage-independent and voltage- dependent protective equipment is not made in English-speaking norms and not used in the IEC and EN standards. In the international device standards following designations are used:

RCCB = Residual Current Operated Circuit Breaker without over current protection conforms to the pure FI or DI switches ( equivalent to RCD residual - current device )
RCBO = Residual Current operated circuit- breakers with integral over current protection corresponds to the combined FI/LS- and LS / DI switches,
SRCD = socket outlet with residual current operated device, are FI or DI sockets ( these protective devices are intended for installation in sockets )
GFCI = Portable Residual Current Operated Device, are non-stationary, most commonly found among personnel protection adapter,
RCU = Residual Current units are fault-current trigger for mounting on circuit breaker,

CBR = Circuit Breaker Incorporating Residual current protection, are circuit breakers with residual current protection function.
GFCI = Ground Fault Circuit Interrupter, is the term used in North America for RCCB

In the installation regulations for electrical equipment fault current protective switches are managed uniformly under a parent term RCD. A differentiation between FI, DI or special designs is no longer made in the regulations for electrical installations. Here the objective of protection is crucial. This must be implemented depending on the location with different designs.

Regulations

The use of residual current devices in many countries in the domestic and industrial sector, at least for sockets (up to 20 A or 32 A ) (about DIN VDE or OVE ) in addition to the installed overcurrent protection bodies absolutely need. A residual current circuit breaker with a trip current of 300 mA difference is as fire protection of the entire electrical system of some power companies often prescribed when the house feed is not via underground cables, but via the roof overhead lines.

Are in Europe, except Britain, voltage-independent residual current device (RCD ) has been imposed. The underlying safety philosophy, the reliability of the electronic amplifier circuits in question, which in the simpler and smaller electronic DI switches ( residual current circuit breaker) are used in the English-speaking world.

Germany

In Germany, residual current circuit breaker since May 1, 1984 required for rooms with bath or shower in new buildings ( the only exception being permanently connected water heater ). Since 1 February 2009, also have all the sockets circuits with a rated current up to 20 A, which are intended for use by laymen and for general use, be equipped with a residual current protective device with a rated residual current of 30 mA ( in new buildings in the outer region for final circuits up to 32 A ).

The standards are binding for the DIN VDE 0100-701:2008-10 ( for rooms with bath or shower) and DIN VDE 0100-410:2007 (Section 411.3.3 - for socket circuits ). The transition period for the previously previous edition 1997-01 expired on 1 February 2009.

For indoor pools and outdoor pools as well as for rooms and cabins with sauna heaters, there is also the requirement for RCDs.

The often misleadingly applied term " wet room " does not refer to bathrooms or toilets in homes. As defined in DIN 68800 is a humidor when a humidity above 70 % is present in the longer term. In DIN VDE 0100-200:2008-06 section NC.3.3 kitchens are explicitly classified in homes and bathing rooms in apartments and hotels in terms of installation as dry rooms (since in these rooms only temporarily moisture occurs).

A "wet room " according to VDE 0100-200 Section NC.3.4 is a room or a specific area within a room, in which the safety of electrical equipment by humidity, condensation or similar climatic influences may be impaired.

A " wet room " according to VDE 0100-200 Section NC.3.5 is a room or a specific area within a room whose floor - sometimes the walls and / or facilities - are hosed from operating, hygienic or other reasons with water.

For older systems, there is no retrofit requirement. That is, a system must continue to operate if the facility has complied with at the time of its establishment the then prevailing standards and guidelines and these are still equal.

In Germany, however, under the following circumstances, the retrofitting of a residual current circuit breaker inevitable if:

Use changes are made
Terms extensions, alterations or renovations, which engage in the substance
New legal regulations that require retrofitting note TAB
Elapsed transition periods
Immediate risks to persons and property

Note: The mere exchange of a resource on the example of a socket does not require adaptation to new standards. However, if the outlet moved to a new location or expanding a socket circuit to another outlet, then at least this circuit is adapted to the current state of the art (standard position ).

You must also wait in agriculture, especially in animal husbandry, residual current circuit breakers are used. The reduction of permanently authorized contact voltage to 25 V AC and 60 V DC voltage has been dropped according to DIN VDE 0100-705:2007-10.

Austria

In Austria, a residual current circuit breaker with a rated fault current of max. 30 mA to OVE E8001-1/A1 :2010- 02-01 required for all circuits, in which there are power outlets and a rated current not exceeding 16 A.

On building sites for all socket circuits with a rated current up to 32 A and in agricultural and horticultural premises ( not in the adjacent apartment buildings ), in sauna, swimming pools, swimming outdoor installations, the experiment stands in classrooms, medical rooms, bathrooms, campsites, boat landings, sconces in the hand area of dressing rooms regardless of their rated current to provide an additional protection.

Switzerland

In Switzerland, according to low voltage installation standard ( NIN) 2005 4.7.2.3.1-8 max. 30 mA required for bath and shower rooms, electrical outlets outdoors, damp and wet rooms corrosive environments and explosive atmospheres, construction sites, exhibition centers, fairs, fairgrounds, elec. Experimental arrangements. (both all sockets ≤ 32 A).

300 mA are required for installations in corrosive environments, explosion and fire risk, as well as in agricultural holdings for the entire installation, in agriculture all connectors with 30 mA RCDs must be fitted.

From 1 January 2010, the new NIN 2010 came into force. From now on every freely accessible outlet must be ≤ 32 A with a max. 30 mA RCD fused. Exceptions are for example: electrical outlets in IT systems where the reliability is more important, and the room with access control can only be accessed by a group of persons instructed.

Area of application

In IT systems the entire low-voltage installations must be protected. For new construction, today nothing speaks against it to secure the complete power supply. There is now provision to build at least two RCDs in a housing mailing list so that does not shut down the entire system in case of failure. This may be inconvenient in certain circumstances, so you should limit the protected by residual current circuit breaker circuits. When selecting and any leakage currents electronic loads (eg ECG) or their potential of Residual must be observed (eg, built- in frequency inverter washing machine). When retrofitting of older buildings often leads to false tripping of residual current circuit breaker, whose cause is sometimes difficult to narrow it down. Often wrong wiring can be the cause, in which flows off current through the protective conductor rather than through the neutral conductor, for example, in electrical outlets or water heaters.

Shutdown by residual current circuit breakers can also be caused by external events, for example by voltage pulses due to lightning in overhead lines. This can often lead to unpleasant side effects such as shutdowns of heating or cooling systems, although no error in the own system exists. For this reason, circuit breakers have been developed that automatically intrude again at a short distance after releasing two to three times the voltage. Only if the error persists, they remain permanently switched off. These models are mainly for remote installations of interest where no staff on site, which could turn the circuit breaker again.

System errors can be found quickly if the end circuits have switched or interruptible by isolating terminals neutral.

Check the residual current circuit breaker

Button for function test ( test button )

On earth leakage circuit breaker is a test button (T), with the function of the device can be tested: an outgoing outer conductor is connected via a suitably sized resistor connected to the neutral conductor from the fault current protection switch. So is wanted, a fault current generated exceeds the trip current. However, this release does not ensure that the circuits are wired correctly to the consumers. The overall function of the system can be ensured with suitable testing equipment. For testing the exact tripping current and the tripping time it requires a RCD test according to DIN VDE 0100-600, the acc. BGV A3 (p. 12) is carried out by a qualified electrician.

Manufacturers recommend at least biannual examination by the user.

RCD test according to DIN VDE 0100-600 (as of 06-2008 )

According to DIN VDE 0100 part 600 is the effectiveness of the protective measure " Automatic break in power supply " evidence. The appropriate requirements according to DIN VDE 0100-410 must be observed.

With the differential current measurement IΔn the function of a residual current circuit breaker can be tested. The measured value is between 50% and 100 % of the rated fault current. In practice, the value is around 70%.

The maximum break according to DIN VDE 0100-410 is for socket circuits up to and including 32 A in TN systems 0.4 s ( at 230 V to earth, in a TT system 0.2 s ). In practice, this value is around 20 ms -40 ms. The opening time for the device itself is by building standard (DIN EN 61008-1, VDE 0664-10 ) at full IΔn 0.3 s, at 2xIΔn 0.15 s and 0.04 s 5xIΔn

In addition, the contact voltage and the ground resistance is measured, this may not exceed specified in the standard values . The effectiveness of the automatic shutdown of the power supply by residual current devices (RCDs ) must be checked with suitable measuring instruments according to DIN EN 61557-6 ( VDE0413 -6). The measured values are to be documented in the appropriate test reports, which may for example be a ZVEH test report.

RCD test type A ( Switzerland )

An electrician turns the switch from always with the test button. He must, in addition to the test button to simulate a 30 mA residual current circuit breaker residual current of 50 % of the rated tripping current. The RCD must hold. Then, a current is simulated in the size of the nominal residual current and residual current circuit breaker must trip according to DIN 2010 Section 4.1 within 0.4 s. They are small and Test Instruments installation tester on the market that allow this examination from the outer conductor to the ground conductor. The tripping time is recorded in the safety case for a 30 mA RCD which are in practice 20 to 30 ms. Short-time delayed residual current circuit breaker require 40 to 100 ms.

Selective residual current circuit breaker with 300 mA for Fire and corrosion protection trigger in the pulse method (50 % and 100 % fault current) approximately in 200 to 400 ms, the standard ( NIN 6.1.3.9 / EN 61008-1 ) requires 130 to 500 ms.

History and development

The residual current circuit breaker was in 1903 under the name of Schuckert total current circuit for earth fault detection patented ( DRP-Nr. 160 069 ). Kuhlmann describes AEG a method for measuring the earth fault currents in the Berlin network. Is further developed the technology, on which also present residual current circuit breakers are based, by Nicholson (1908, U.S. Pat no. 959 787 ).

In the early 1950s, after countless suggestions and technical studies on the basic applicability of the circuit for the first time presented as a protective device a mature residual current circuit breakers for the widespread use of the electricity customers. Busy is in it for 1951 Residual current circuit breakers of the company protection devices Society & Co. mbH. KG, Schalksmuehle / Westphalia. ( Schupa ) with the trade name cobweb, which was designed in two -, three - and four-pole version for a nominal current of 25 A and voltages up to 380 V with a tripping fault current of 0.3 A. A lower trigger threshold was discussed but rejected as economically unsound. The time allowable leakage in heating devices have resulted in a lower trigger threshold also in frequent false alarms.

In 1957, Gottfried Meier Biegel developed in Austria at Felten & Guilleaume a residual current circuit breaker. These were prescribed in Austria in 1980 in private households by law, the trip current was gradually reduced from the original 100 mA at 70, 65 and 30 mA. Since early 1985, this applies to the entry into force of the provision SEV 1000-1.1985 in Switzerland.

Similar facilities

Protection management system - An Isolationsprüfeinrichtung in special facilities
PRCD -S - A mobile residual current device that is connected in the supply of equipment
Residual Current Monitor - A monitoring system for display of fault currents

Standardize

DIN VDE 0100-100:2009-06 Erection of low -voltage electrical installations Part 1: General principles, rules of general characteristics, definitions.
DIN VDE 0100-410:2007-06 Erection of low -voltage equipment, Part 4-41: Protection for safety - Protection against electric shock.
DIN VDE 0100-530 :2011 -06 Erection of low voltage installations, Part 530: Selection and erection of electrical equipment - Switchgear and control equipment. " Standard national character only for Germany ".
DIN VDE 0100-600:2008-06 Erection of low voltage installations, Part 6: Tests.
DIN VDE 0100-701:2008-10 Erection of low -voltage electrical installations - Part 7-701: Requirements for special installations or locations and special installations or locations - Locations containing a bath or shower.
DIN VDE 0100-705:2007-10 Erection of low voltage installations, Part 7-705: Requirements for special installations or locations and special installations or locations - Electrical installations of agricultural and horticultural premises.
DIN EN 61008-1 VDE 0664-10:2010-01 breakers without integral overcurrent protection ( RCCB ) for household and similar use Part 1: General requirements.
DIN EN 61557-6 VDE 0413-6:2008-05 Electrical safety in low voltage distribution systems up to 1 000 V ac and 1 500 V dc - Equipment for testing, measuring or monitoring of protective measures Part 6: Effectiveness of residual current devices (RCD ) in TT, TN and IT systems.
OVE E8001-1/A1 :2010- 03-01 Construction of electrical installations with nominal voltages up to 1000 V ac and 1500 V dc, Part 1: Definitions and protection against electric shock (protection measures)

Electric power distribution Distribution network operator Electrical polarity Earthing system Overhead power line Ampere Water heating#Tankless heaters

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