Differential protection device including a rectifier and a toroid having a nanocrystalline core

A differential protection device for an electrical installation sensitive to pulsed currents, comprising

• (a) a differential transformer including a toroid having a magnetic core formed of nanocrystalline material, primary windings formed of the active conductors of the installation, and a secondary winding in which a fault signal is established when a differential fault occurs in said primary windings;
• (b) a tripping relay;
• and
• (c) means connecting said tripping relay with said secondary winding, said connecting means including a capacitor connected in parallel with said secondary winding to define a resonant circuit having a resonance frequency for generating said fault signal as a voltage surge for said relay and rectifier means wherein said rectifier means performs symmetrization of said pulsed current which responds to said fault signal in said secondary winding for activating said tripping relay, wherein said connecting means comprises in addition a storage capacitor and means for comparison, said comparison means being connected to the storage capacitor and comprising a monitoring output connected to a control means of the relay to supply a tripping signal to the relay if the value of the voltage of the storage capacitor is greater than a preset threshold.