Fault line detection in neutral point ineffectively grounding power system based on phase-locked loop

Fault line detection timely and accurately when single-phase-to-earth fault occurs in neutral point ineffectively grounding power system is still a focus of research. To perfect these existing detection methods and enhance their accuracy, an improved phase-locked loop (IPLL) is used to extract the fifth harmonic zero-sequence currents in this study and fifth harmonic current characteristics are employed to select the fault line. Through relative processing, the fifth harmonic data differences of all lines are more noticeable, which is better for fault line detection. The line-detection function of IPLL is shown based on Matlab/Simulink. Simulation result reveals the good performance of this proposed method in effectively fault line detection. This method is able to detect different types of grounding faults in power system. This study gives a new train of thought for fault line detection.