Electronic tripping device for low-voltage circuit-breakers

An electronic tripping device for low-voltage circuit-breakers, in particular for low-voltage multipolar automatic circuit-breakers, comprising means for detection and calculation of a ground-fault current operatively connected to tripping means of said circuit-breaker, said means for detection and calculation comprising:

• current-sensor means that supply, for each pole, a signal proportional to the current circulating therein;
• means for detection of the sign of the current, the input of which is operatively connected to said current-sensor means, which, for each pole, supply at output a two-level signal representing the sign of the current in said pole;
• current-rectifying means, the input of which is operatively connected to said current-sensor means, which, for each pole, supply at output a rectified signal proportional to the current circulating in said pole;
• and
• first numerical-processing means, the input of which is operatively connected to said means for detection of the sign of the current and to said rectifying means, said first processing means supplying at output, with a predetermined periodicity, a value with sign representing a ground fault by means of a numerical-processing operation that comprises multiplication for each pole of said two-level signal with the corresponding rectified signal proportional to the current circulating in said pole.