Patent ID: 8918296

Claim:
A method for detecting single phase grounding fault in a feeder line of a power distribution network, wherein a fault detection device performs the steps of: 1) continuously sampling and calculating the current in the feeder line, and getting the sample value sequence of the residual current in the feeder line; 2) averaging the sample value sequences of N cyclic waves prior to the present residual current in the feeder line, to get the average sample value sequence, wherein N is a positive integer; 3) getting a fault increment sequence by the present sample value sequence of one cyclic wave minus the average sample value sequence; 4) calculating the third harmonic component amplitude and phase and the fundamental amplitude and phase of the fault increment sequence with Fourier transform, and getting the phase difference of the residual current in the feeder line by the third harmonic phase minus the fundamental component phase; 5) if the phase difference of the residual current in the feeder line falls within a predetermined threshold range, determining that a suspected grounding fault occurs in said feeder line occurs; and 6) judging the duration and the occurrence of the suspected grounding fault with three timers and a counter, to identify a grounding fault, an intermittent grounding fault, transient events or noise.