Active Location Method for Single-Line-to-Ground Fault of Flexible Grounding Distribution Networks

The single-line-to-ground (SLG) fault is the most common fault in distribution networks. The output current of cascaded H-bridges (CHBs) can be controlled flexibly to suppress SLG fault current. Therefore, a CHB-based active location method is proposed in this article, which integrates the functions of SLG fault arc suppression, fault section location, and fault nature judgment. When an SLG fault occurs, CHB devices quickly inject full compensated current into the system neutral to suppress the fault current. Then, CHB devices are regulated to reduce the injected current, and the variations of zero-sequence voltage and zero-sequence current are actively constructed. The phase characteristics between zero-sequence voltage variation and zero-sequence current variation can be used as the criteria for fault section location and fault nature judgment. In addition, the measurement device, namely, the retrofitted feeder terminal unit (FTU), contains signal acquisition module, and signal calculation module is designed, which can collect the zero-sequence signal and calculate the phase difference. Finally, the effectiveness of these three functions and the fault-location accuracy of the proposed method have been verified through the simulation and experimental cases.