Residual current monitoring type B with integrated self-test system and method

A system, comprising:

• a residual current sensor configured to sense a residual current from a source of AC power, comprising:
• a first core comprising:
• a first excitation coil winding;
• and
• a first secondary coil winding;
• a second core comprising:
• a second excitation coil winding;
• and
• a second secondary coil winding;
• and
• a DC null winding configured to wind through both the first core and the second core;
• a residual current sensor circuitry electrically coupled to the residual current sensor comprising a controller electrically coupled to the residual current sensor circuitry, the controller comprising:
• one or more processors;
• and
• a memory configured to store data and instructions executable by the one or more processors, wherein the instructions include:
• transmitting an excitation voltage to an excitation path of the residual current sensor circuitry;
• receiving an unbalanced current signal from a detection path of the residual current sensor circuitry;
• determining a DC residual current contribution to the unbalanced current;
• calculating a DC injection scheme configured to negate the DC residual contribution;
• injecting a DC current into a DC nulling path of the residual current sensor circuitry based on the DC injection scheme;
• receiving a balanced current signal from the detection path;
• and
• determining an AC residual current.

A method, comprising:

• transmitting an excitation voltage to an excitation path of a residual current sensor circuitry;
• receiving an unbalanced current signal from a detection path of the residual current sensor circuitry;
• determining a DC residual current contribution to the unbalanced current signal;
• calculating a DC injection scheme configured to negate the DC residual contribution;
• injecting a DC current into a DC nulling path of the residual current sensor circuitry based on the DC injection scheme;
• receiving a balanced current signal from the detection path;
• and
• determining an AC residual current.