Patent ID: 8390302

Claim:
A method of detecting and analyzing faults in a three phase feeder system having a first cable and one or more other cables, the method being performed by at least one computer and comprising: receiving a mode selection from a user through a user interface; determining current magnitude in the first cable; comparing the current magnitude to a threshold level; when the current magnitude exceeds the threshold level, starting a counter of the at least one computer; when the current magnitude falls below the threshold level, stopping the counter and determining from the counter how long the current magnitude stayed above the threshold level; when the current magnitude is determined to have stayed above the threshold level for a duration that falls within a predetermined duration range having lower and upper levels, starting a timer; after the timer measures a predetermined time interval, determining whether a fault is detected in the one or more other cables during the predetermined time interval; and when a fault is not detected in the one or more other cables, determining that a single phase fault has occurred in the feeder system; wherein when the mode selection is an adaptive mode, the threshold level is the greater of a fixed minimum value and an adaptive value calculated from prior current magnitudes, and wherein when the mode selection is a fixed mode, the threshold level is a preset value received from a user through the user interface.