Modified FFT based high impedance fault detection technique considering distribution non-linear loads: Simulation and experimental data analysis

- The capability of detecting HIFs at the presence of non-linear loads.
- The capability of distinguishing normal switching events from HIFs.
- The ability to assess networks with/without the presence of non-linear loads.
- The independency towards fault location, resistance and current magnitude in feeders.

High Impedance Faults (HIFs) have been labeled as the most common disturbances in the power distribution systems. The special circumstances created by these faults mislead traditional protection equipment. The low magnitude and unpredictable nature of current correspond to many false detections and operators distrust in available installed protection schemes. Moreover, the nowadays harmonic rich content of distribution grids plays a significant role in increasing confusion for protection relays. The FFT approach has been utilized as an adequate detector of HIFs in regards to typical linear loads. The majority of available methods neglect the presence of non-linear loads. In the presented paper, a modified scheme has been engineered to compensate for this fact. The harmonic analysis of the sum of all three phase currents has shown to be a better substitute for the traditional feeder current. Numerous simulations via the IEEE 13-Node distribution system and experimental data analysis of “Palash” distribution system have shown promising results. The proposed scheme has shown to be capable of detecting and distinguishing between HIFs and normal events, i.e. capacitor bank and load switching. The presence of non-linear loads has been effectively detected and isolated from the procedure of HIF detection.