Residual current blocks
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.
Protection against electric shock
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.
Protection against the effects of short circuits and overloads
Fuses are responsible for protection against the effects of short
circuits and overloads , collectively referred to as overcurrents.
Residual current blocks for circuit breakers
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 for power fuses
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.
Apparatus EATON, Legrand and Schneider - excellent quality and many possibilities
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:
- phase and neutral (1 pole),
- two phase and neutral (3 poles),
- three phase and neutral (4 poles).
Most brands known on the market of electric apparatus also produce
residual current blocks for power fuses.