Patent ID: 7248057

Claim:
Apparatus for detecting an incipient ground fault that may occur in an electrical propulsion system of a traction vehicle, said electrical propulsion system comprising a plurality of electrical devices, each individual electrical device being potentially subject to an incipient ground fault in at least one electrical phase thereof, said apparatus comprising: a sensor configured to sense a respective ground leakage signal associated with a ground of the propulsion system; a correlator coupled to the sensor to receive the ground leakage signal and further coupled to receive at least one signal indicative of a respective energization state of a respective electrical phase for each respective one of the plurality of electrical devices, said correlator configured to individually correlate the ground leakage signal with each received phase energization state signal, and supply an individual correlation signal between the ground leakage signal and each received phase energization state signal, wherein said correlator comprises a plurality of m correlators, each of said m correlators being individually connected to receive one signal indicative of a respective energization state of a respective electrical phase of one of the plurality of electrical devices, wherein m is a positive integer corresponding to the number of electrical devices times the number of electrical phases per device; a low pass filter connected to the correlator and configured to provide a predefined filtering to the supplied correlation signals, and further wherein said low pass filter comprises a plurality of m low pass filters, each one of said m filters being individually connected to one of said m correlators to provide a predefined filtering to one supplied correlation signal; and a processor coupled to the correlator for processing each of the individual correlation signals supplied by the correlator and extract a correlation value from the supplied correlation signals, said correlation value being indicative of an incipient ground fault in a respective phase of one of the plurality of electrical devices.