An Adaptive Technique of Earth Fault Detection and Self-Extinguishing by Controllable Petersen-Coil

The paper discusses the characteristic of single phase fault in Petersen-coil-grounded distribution grid, analyzes the zero sequence voltage and currents of the Petersen-coil, fault point, fault feeder and sound feeders. Adaptive Petersen-coil is applied to help detecting and extinguishing the single earth fault. And the paper studies characteristic of the derivatives of the zero sequence currents of the feeders, and introduces the theory that the fault feeder's zero sequence current changes with the inductance of the controllable Petersen-coil, and the derivative of zero sequence current of the fault feeder is the maximum and far higher than the sound feeders. The equivalent earth capacitance of the grid is measured online, and the inductance of Petersen- coil can be tuned to be in a whole resonance with it, so as to extinguish the fault arc quickly and detect the fault reliably. The paper sets up a simulating model of a Petersen-coil grounded grid, and proves the exactness, availability and sensitivity of the novel fault detecting technique by simulating tests.