Patent ID: 7253633

Claim:
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 fault detection component; 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 a power line of the plurality of power lines; 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, coupled between the localized ground and the system safety ground, and a second capacitor, coupled between the diode and the localized ground in parallel with the voltage divider such that the second capacitor is charged on a positive cycle of the line-to-ground voltage 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 condition 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.