Developments in the field of electrical devices and means of protecting a person from damaging effects electric current made it possible to obtain reliable equipment, which has become indispensable in any the room. One of these devices is an RCD. The decoding of the abbreviation sounds like a "residual current device", and the design itself represents is a set of interacting elements and mechanisms that automatically turn off power in an emergency situations.
Content
- The principle of operation of the device
- Types and marking
- Number of home appliances
The principle of operation of the device
The equipment works to prevent emergency situations as a result of a short circuit or fire inside the wiring, and also protects household appliances connected to the network from burnout. RCD provides protection to humans with sudden electric shock. The design of the residual current device is based on a differential transformer - a core with windings wound on it. Electrical law requires the input and output electrical current to be equal when the network is operating normally and there are no cabling or wiring problems.
The current flowing through the phase must be the same as that flowing through the neutral wire (in single-phase circuits), or equal to the sum of all currents in the phases (in three-phase circuits). In the event of a current leak, such equality is severely violated. This happens when a person accidentally touches conductive elements that are not protected by insulation, or when a piece of bare wire comes into contact with other conductive objects.
The residual current device (RCD) reacts to an equality failure by receiving a command to de-energize the entire network. In the field of electrical engineering, the leakage current is called differential. Modern highly sensitive models are capable of detecting even the smallest leaks and tripping. Thus, with the RCD, protection is provided:
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when the phase is closed to the housing of household appliances (washing machines, heaters and water heating tanks are predominant); - in case of violations committed during the laying of electrical wiring (often builders walled up the twist under plaster without a special installation box, if the wall gets wet, current leakage occurs, the protection is triggered shutdown);
- in case of violations of the rules for installing the electrical panel or changes in the current distribution scheme.
The reason for the operation of an RCD in an electrician is sometimes quite difficult to determine even after a thorough examination of household appliances and their connection diagrams. Connecting the hose of a washing machine in a metal case to water supply, installation of a gas stove with electric ignition, as well as grounding thrown by neighbors to heating devices. In such cases, the assistance of specialists from the energy supervision service will be required.
Types and marking
Manufacturers indicate the correct connection diagram on the RCD cases. This is especially important for those who, with their own hands and without the involvement of specialists, decided to carry out the installation. The marking of each device allows you to choose the most optimal option for specific operating conditions and power grid parameters. All devices, similar in appearance, are divided into two types:
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electromechanical - the polarization relay is marked with a square and is directly connected to the differential transformer, marked as a rectangle with rounded corners; - electronic - the relay is connected to the transformer through the amplifier board, which has a triangle icon.
You can also determine the type of device in another way: bring the magnet to the equipment case, move it near the side parts, and then along the front panel when it is on. If a trip occurs, then the RCD is electromechanical. Otherwise, the device is electronic.
For domestic use, RCDs with a sensitivity of 10 or 30 mA are suitable, and to prevent serious fires and fires, the sensitivity should be 100 mA and 300 mA.
Number of home appliances
To install devices in an apartment or your own house, you need to contact a specialist. Their number is determined by the number of household appliances, lighting fixtures and sockets. The larger the living space, the greater the need for an RCD. For example, in a one-room apartment, one device will cope with the tasks set, and in a four-room apartment, at least 5 pieces will be required. Such devices must be installed on:
- lighting devices;
- gas stoves with electric ignition;
- water heating tanks;
- washing machines;
- sockets.
A device sensitive to a leakage current of 300 mA (fire-prevention input RCD) must be installed at the common input in the switchboard. It should be borne in mind that if there is old wiring with damaged insulation in the house, the protective device will work constantly. Therefore, it is recommended to either update the wiring during the next repair, or mount the sockets with mini-RCDs mounted in them.
The need to install devices that perform a protective shutdown is due to the sharply increasing the number of electrical appliances used in each home, as well as the increased threat of human injury electric current.
