Wednesday, 12 August 2020
Saturday, 18 July 2020
Discrimination between residual current circuit breakers (RCCBs)
Generalities and discrimination between RCDs
The
operating principle of the residual current release is basically the
detection of an earth fault current, by means of a toroid transformer
which embraces all the live conductors, included the neutral if
distributed.
In absence of an earth fault, the vectorial sum of the currents IΔ is equal to zero.
In case of an earth fault, if the IΔ value exceeds the rated residual operating current IΔn, the circuit at the secondary side of the toroid sends a command signal to a dedicated opening coil causing the tripping of the circuit-breaker.
Figure 1 – Operating principle of the residual current device
Classifications of RCDs
A first classification of RCDs can be made according to the type of the fault current they can detect:
- AC type: the tripping is ensured for residual sinusoidal alternating currents, whether suddenly applied or slowly rising;
- A type: tripping is ensured for
