The residual current device (also called the differential, residual current device or electric shock switch) is an electrical device that protects the electrical installation, which disconnects the circuit after detecting that the value of the current flowing into it is not the same as the outgoing current (according to Kirchhoff's first law).

The main task of this equipment is to protect people from electric shock when directly or indirectly touching a given device. In addition, residual current circuit breakers minimize the risk of damage to individual devices connected to the network and fire in the building.

History of RCDs

The first devices that today can be considered prototypes of modern residual current devices were created in the 1950s in South Africa. They were developed by Henri Rubin – an engineer working for C.J. Fuchs Electrical Industries. The protection system he invented, based on the so-called cold cathode in the blink of an eye gained fame and was widely installed, among others in gold mines. Over time, these solutions were improved and began to be installed in factories or even households. The widespread use of RCDs dates back to the early 1970s.

Construction of residual current circuit breakers

Residual current circuit breakers are made of four basic elements – current circuit contacts (along with a lock and a switching lever), a residual current release (usually in the form of a polarized relay), a Ferranti transformer, i.e. a special ferromagnetic ring through which the neutral and phase conductors pass, and also from the breaker test circuit – a special subassembly that allows checking the operation of the device during operation.

Principle of operation of the residual current circuit breaker

According to the aforementioned Kirchhoff's first law - the vector sum of the currents flowing through the transformer is equal to zero during normal operation. However, if the so-called leakage current, then the sum of currents in the transformer window will have a different value, which should be considered an extremely undesirable phenomenon. The main task of the differential is in such a situation to disconnect the installation from the power supply. The special structure of the equipment makes it react to failures automatically.

Types of residual current circuit breakers

Basics The division is based on the criterion of the operated tripping current. In this way, there are high-sensitivity circuit breakers that respond to currents of less than 30 mA, medium-sensitivity (range 30-500 mA) and low-sensitivity, i.e. those that only operate on currents exceeding 500 mA.< /p>

Another classification is based on the type of leakage current detected. On this basis, AC circuit breakers are distinguished – sinusoidal alternating current, circuit breakers A – rectifiers detecting alternating sinusoidal residual current, rectified half-wave and impulse current, as well as type B circuit breakers that additionally handle direct current.

The circuit breakers also differ in terms of built-in overcurrent protection. The RCCB models do not have this type of arrester, unlike the copies marked with the RCBO symbol. Circuit breakers may also differ in the number of poles and rated voltage supported. The latter should not be lower than the mains voltage to which the equipment will be connected

Use of residual current circuit breakers

They are primarily an additional protection, next to the so-called. automatic power off, in TN-S TN-C-S and TT systems. They are less often installed in IT systems.

For an RCD to function properly and fulfill its function, it is important to use it properly. It is recommended, among others to use the test button once a month to verify the correct response to a possible network failure. If the circuit breaker trips immediately, it is operational. It should be remembered that such a test should be carried out without loading the network with high-power receivers.

Residual current circuit breakers will reduce the risk of fire. However, you must be aware that this is not a typical fire-fighting equipment. It does not protect directly against fire and does not extinguish it. The equipment is only intended to make the potential ignition of the installation less likely.

What's more – One more issue needs to be clarified - the RCD does not protect against electric shock in all situations. When in contact with a protective conductor and the current flows directly to the ground, a person will always be exposed to shock, but probably less than in the case of touching an unprotected conductor and to the extent not threatening life or health. In addition, the differential will not provide protection against electric shock when two protected conductors (for example, phase and neutral) are touched and the person is isolated from the ground.

Residual current circuit breakers in the offer of the online store

We have a wide selection of classic models, with protection and the so-called. anti-shock protection tubes. Everyone should find a copy here tailored to their individual needs. We have models that differ in the type of differential current supported – A, AC, B, C and even D. Individual units support voltages of 120, 230, 400 and 415 V. It is also possible to choose residual current devices due to the number of poles (from 1 to 4). In addition, the offer of the store includes fuses supporting residual current of 10, 100, 300, 500, 1000, 3000 and even 10000 mA and rated current in the range from 6 to 125 A.

We have residual current devices coming only from reputable manufacturers of this type of equipment. We offer products of such brands as ABB, ETI Polam, Hager, Legrand, Eaton, Noark and Schneider Electric.

We make every effort to ensure that the ordered products reach customers as soon as possible. The standard lead time is about 3 working days. This applies to the assortment that is currently in stock. However, it happens that a given product is temporarily unavailable and you have to wait for its delivery. At that time, the execution of the order may take up to several weeks. Information about stock levels is always available on the product card under the technical specification. If you have any doubts about the availability of the assortment, please contact the Customer Service Department.