Single Phase Ferroresonance Detection and Type Recognition in Solidly Grounded Power Grid

The nonlinear characteristics shown by ferroresonance are the basis for effective ferroresonance detection algorithm design. However, due to the lack of field recorded data and analytical solutions for the resonant circuit, it is difficult to quantitatively analyze the phenomena and thereby design the detection methods. What is more, there are faults that show similar waveform characteristics with ferroresonance in the field, mainly High Impedance Faults (HIF). Because of these reasons, reliability and accuracy of existing ferroresonance detection methods leave room to be improved. In this paper, the time domain analytical solution of Single-phase Series Ferroresonance (SSF) and HIF in solidly grounded power grid are obtained through piecewise linearization. The analytical solutions are quantitatively analyzed to retrieve fault signatures. The phase current mean envelope curve and phase voltage spectrum are then found to be dependable and accurate signatures for fault detection and they are utilized to construct the proposed detection method. The volt-ampere characteristics is found to be the signature to differentiate SSF with other faults, mainly HIF. The effectiveness of the detection algorithm is verified against simulation data, proving the algorithm's capability of protecting the grid against SSF and HIF.