ABB CI840 Analog module industrial system controller

Description

Packaging details: if you need an urgent delivery order, please feel free to contact us, and we will do our best to meet your needs.

Price problem: if you find that other suppliers offer cheaper prices for the same product, we are also willing to provide you with reference prices and give you further discounts.

RCDs can be coupled, or not, with other devices; it is possible to distinguish
among:
– pure residual current circuit-breakers (RCCBs): they have only the residual
current release and can protect only against earth fault. They must be coupled
with thermomagnetic circuit-breakers or fuses, for the protection against
thermal and dynamical stresses;
– residual current circuit-breakers with overcurrent protection (RCBOs): they
are the combination of a thermomagnetic circuit breaker and a RCD; for this
reason, they provide the protection against both overcurrents as well as earth
fault current;
– residual current circuit-breakers with external toroid: they are used in industrial
plants with high earth fault currents. They are composed by a release
connected to an external toroid with a winding for the detection of the residual
current; in case of earth fault, a signal commands the opening mechanism of
a circuit-breaker or a line contactor.
Given I∆n the operating residual current, a very important parameter for residual
current devices is the residual non-operating current, which represents the
maximum value of the residual current which does not cause the circuit breaker
trip; it is equal to 0.5 I∆n. Therefore, it is possible to conclude that:
– for I∆ < 0.5⋅I∆n the RCD shall not operate;
– for 0.5⋅I∆n < I∆ < I∆n the RCD could operate;
– for I∆ > I∆n the RCD shall operate.
For the choice of the rated operating residual current, it is necessary to consider,
in addition to the coordination with the earthing system, also the whole of the
leakage currents in the plant; their vectorial sums on each phase shall not be
greater than 0.5⋅I∆n. in order to avoid unwanted tripping.
Discrimination between RCDs
The Standard IEC 60364-5-53 states that discrimination between residual
current protective devices installed in series may be required for service reasons,
particularly when safety is involved, to provide continuity of supply to the parts
of the installation not involved by the fault, if any. This discrimination can be
achieved by selecting and installing RCDs in order to provide the disconnection
from the supply by the RCD closest to the fault.
There are two types of discrimination between RCDs:
– horizontal discrimination: it provides the protection of each line by using a
dedicated residual current circuit breaker; in this way, in case of earth fault,
only the faulted line is disconnected, since the other RCDs do not detect any
fault current. However, it is necessary to provide protective measures against
indirect contacts in the part of the switchboard and of the plant upstream the
RCD;