Recently, on the windows of electrical engineering stores, you can see a curious device, denoted by the abbreviation RCD. Although there is nothing revolutionary in the basis of his work, right now it has proved to be incredibly in demand.
It's simple: if earlier the electrical equipment of an average apartment included several incandescent lamps, a low-power iron and a TV with a receiver, now the list has expanded significantly. Accordingly, the potential probability of electric shock to a person has also increased. As you know, the best protection in such a situation is the installation of a ground loop and the connection of all electrical equipment to it. However, this is not always possible. In addition, it is much easier to carefully connect the RCD next to the electric meter, rather than pull the lines from all devices to the protective circuit.
Nothing complicated
The principle of operation of this protective device is based on comparing the effective values of two currents - flowing through the phase and zero branches. In the normal state, they are equal (or the delta is within acceptable limits), but the appearance of a difference is interpreted by the circuit as a dangerous leak, and the RCDturns off. To understand what is the connection scheme for RCDs and automata, it is necessary to clearly understand the above principle. So let's use the analogy of a container and a liquid. Let some abstract pressure tower be an apartment with all electrical consumers. Two tubes are brought out of it - an “inlet” for supplying water and an “outlet” for draining. Obviously, as long as the tower is intact, the amounts of incoming and returning liquids are equal. But as soon as there is less water at the outlet, we can talk about a leak. Moreover, by the magnitude of the difference, it is possible to indirectly determine how great the damage to the pressure tower is. It is easy to understand that the electric current should not leave the circuit anywhere. If this happens, then a leak has occurred somewhere, or, perhaps, the meter “windback” scheme is used. Having understood this, you can study further how the RCD is connected.
Electrical Protection Philosophy
Let's imagine that the wire insulation was damaged in the washing machine circuit, and the phase (current) appeared on the metal case. When touched, current flows through the human body, which is deadly. To prevent this, you need to connect the RCD. In this case, the device will detect the difference between the incoming and outgoing currents and instantly turn off the common power circuit.
Connecting an RCD
Installation of the device is simple and easy even for a novice electrician. However, first you need to decide where exactly the RCD will be installed. There are three options: directly to the linepower supply of any device; to the branch of the device group; for the whole house. The first method is the most secure, but many protective devices may be required. The second is a compromise, and the third is the least expensive, but has the lowest sensitivity to leaks. There are four output terminals on any RCD: two for phase and zero supply and two for output. There are always corresponding symbols next to them, so it is almost impossible to confuse anything. So, there is a phase wire for supply and the same name for the output from the RCD. For zero, the situation is similar. Please note that it is impossible to let "zero" bypass the RCD (remember the principle of operation).
The easy way
Let's take a simple method as an example. It is he who is most often used when connecting an RCD in the country. The sensitivity of the inlet mounting device should be between 100 and 300 mA (lower values may cause false alarms). Compare: to protect one device (for example, a washing machine), an RCD with a current of 10 mA is required; and for the protection of the whole group - at least 30 mA. So, regardless of whether only an RCD or a differential machine is used (a switch combined with a protective device), this solution is always connected after the main input machine. That is, two wires from the switch go to the input of the RCD, and from its output - further. With this connection, the installation is usually carried out on the meter panel.
