Threshold adjustment accuracy for ground fault condition determination

An apparatus, a polyphase power system with a system safety ground, wherein the polyphase power system supplies a plurality of power phases over a respective plurality of power lines to power a load, the apparatus comprising:

• a power status component that serves to indicate a current status of the plurality of power phases of the polyphase power system;
• a fault detection component;
• and
• an alarm component that comprises an operational amplifier circuit that serves to promote an increase in an accuracy of the determination of the existence of the one or more ground fault conditions through a reduction of one or more effects of transient leakage currents in the polyphase power system;
• wherein the fault detection component comprises a plurality of phase fault detectors that monitor the plurality of power lines, respectively;
• wherein the plurality of phase fault detectors comprise a phase fault detector that monitors the plurality of power lines, respectively;
• wherein the phase fault detector comprises a diode, coupled with the power line, and a voltage divider, coupled with the diode, that outputs a threshold voltage, wherein the threshold voltage comprises a line-to-ground voltage relative to a localized ground;
• wherein the fault detection component comprises a first capacitor, between the localized ground and the system safety ground, and a second capacitor, coupled between the diode and the localized around in parallel with the voltage divider, wherein the first and second capacitor comprise an adjustable capacitance ratio;
• wherein the first capacitor provides a direct current offset to the localized ground upon a ground fault condition;
• wherein the phase fault detector compares the threshold voltage with a reference voltage to make a determination of an existence of the ground fault in the power line;
• wherein the phase fault detector adjusts a sensitivity of the determination of the existence of the ground fault condition in the power line by changing the adjustable capacitance ratio.

A method for making a determination of an existence of a ground fault condition in, a polyphase power system with a system safety ground, wherein the polyphase power system supplies a plurality of power phases over a respective plurality of power lines to power a load, the method comprising the steps of:

• adjusting a voltage divider of a fault detection component to promote an accuracy for adjustment of a threshold for a determination of an existence of one or more ground fault conditions in one or more of the plurality of power lines;
• making a comparison of a divided voltage from the voltage divider and a reference voltage;
• adjusting a capacitance ratio between a first capacitor, between a localized ground and the system safety ground, and a second capacitor, between one power line and the localized ground, to adjust a sensitivity of the determination of the existence of the one or more ground fault conditions in the one or more of the plurality of power lines;
• and
• making the determination of the existence of the one or more ground fault conditions in the one or more of the plurality of power lines based on the comparison of the divided voltage from the voltage divider and the reference voltage.