Residual current blocks are electrical devices that allow an electrician to quickly and easily implement a system consisting of a residual current device and a fuse. The resulting set protects electric circuits against electric shock as well as the effects of short circuits and overloads.
Residual current device (RCD), the basic element of a residual current block, has been designed in such a way as to protect human health and life. In the event of an electric shock, it immediately cuts off the power supply, often saving a person from death. Currently, differentials are used in both industrial and domestic installations. In the latter case, the RCDs operate on all electrical circuits installed in the apartment. In addition to protection against electric shocks , RCDs also function as fire protection. In the event of damage to the insulation of the device connected to the installation or its circuits - the differential interrupts the power supply, thus preventing not only the destruction of the cable or the receiver, but also fire.
Fuses are responsible for protection against the effects of short circuits and overloads , collectively referred to as overcurrents.
In modular differential blocks, the function of fuses is performed by overcurrent circuit breakers (so-called "es", mounted on the poles of these blocks). Miniature circuit breakers used for installation in modular blocks are also implemented as modular. Designed for installation on a TH35 rail, they are designed for maximum voltages up to 440 V AC, rated currents up to 125 A and breaking currents of 25 kA. Their time characteristics are marked with letters from A to E and further K, L, S, Z. In general-purpose electrical installations, overcurrent switches with B (lighting circuits and sockets) and C (discharge lamps, induction motors) characteristics are most often used. The lighting circuits are usually secured by an electrician with B 6A and B 10A "es", and sockets with B 16A switches.
Residual current blocks are implemented by manufacturers of electrical apparatus also as cooperating with the so-called power fuses. These are protections that will trip in the event of overloads. Due to the excessive current flowing through the fuse for a certain period of time, the fuse element (conductor) heats up and then melts, disconnecting the circuit. Power fuses are characterized by the so-called inverse time-current characteristic: the higher the overcurrent, the shorter the break time delay. After a single actuation, the fuse link is destroyed and must be replaced with a new one to restore the fuse's ability to function as intended.
Modular residual current blocks offered by leading manufacturers of electrical equipment and devices such as EATON, Legrand or Schneider , were created to meet the needs of installers. They facilitate assembly, enabling quick installation of the switch on the poles of the block. When choosing an overcurrent circuit breaker from a wide range of manufacturers, the electrician must of course remember to select the appropriate device. It takes into account, among others maximum allowed current leakage, amperage and number of phases. The blocks are implemented as 2, 3 and 4 poles, which corresponds to a wiring arrangement with cores:
Most brands known on the market of electric apparatus also produce residual current blocks for power fuses.
