System for protecting an electrical circuit for an aircraft

A method to detect an insulation fault in an electrical circuit, the electrical circuit comprising a generator, a plurality of electrical apparatuses, each electrical apparatus comprising a chassis, and an electrical protection system having:

• a first electrical link associated with each electrical apparatus, each first electrical link connecting the chassis of said electrical apparatus to an earth, each first electrical link comprising a resistor, called the protection resistor, wherein the protection resistor is arranged such that in case of an insulation fault of said electrical apparatus, said protection resistor passes directly to earth the direct component of the fault current;
• for at least one electrical apparatus operating under direct current, the associated first electrical link comprises a capacitor, called the protection capacitor, in parallel with the protection resistor, wherein the protection capacitor is arranged such that said protection capacitor passes directly to the earth one or more alternating components of the supply current of said electrical apparatus;
• a second electrical link immediately connecting a neutral point of the generator to the earth;
• and at least one voltage detector, each voltage detector being associated with a first electrical link and being configured to measure a voltage across terminals of the protection resistor of the first electrical link, wherein the method is implemented by a fault monitor and comprises, for each voltage detector, the steps of:
• receiving a voltage measurement from the voltage detector, and
• transmitting information representative of an insulation fault in the electrical apparatus associated with the first electrical link that is associated with the voltage detector when the voltage measurement exceeds a predefined voltage threshold.