Fault Location in Resonant Grounded Network by Adaptive Control of Neutral-to-Earth Complex Impedance

This paper proposes a fault location method based on the adaptive control of neutral-to-earth complex impedance in a resonant grounded system, whose neutral point grounds are via an electromagnetic hybrid Petersen coil (EHPC). The EHPC can be equivalent to a parallel circuit of a negative resistance and an inductance, both of which can be adjusted. When a permanent single line-to-earth fault occurs, the ground-fault current will be compensated to almost zero, and the capacitance to earth and leakage resistance of system can be measured accurately for subsequent fault location. Then, the complex impedance of EHPC is adjusted, and the faulty feeder and its faulted section can be identified online based on the characteristics that the measurements of zero-sequence admittances of points along the faulty feeder change with the system's neutral-to-ground complex impedance. The detection criterion is certain and unique, without comparing all of the feeders. This paper also proposes an adaptive jitter adjustment and decoupling control of neutral-ground complex impedance by EHPC, which is adaptive to the grounding transient resistance and is repeatable, and can ensure that the magnitude of the zero sequence parameter is large enough to be measured while without arc re-ignition, including in high impedance fault states. Simulations and experiments verified the feasibility of this fault location method and its control strategy.