Novel Zonal Fault Detection Scheme for DC Wind Farm via Disposition of Surge Arresters in Multipurpose Grounding System

Recently, a prospective new concept of onshore DC wind farms (DCWFs) employing a large-scale grounding system incorporating sheath-connected protective surge devices (PSDs) to ensure protection against probable surges, keep safety of operators, and increase efficacious energy conversion is suggested. This concept involves connecting ungrounded terminal of single-core cable sheath via PSD to conform manufacturers recommendations to avoid thermal stresses. This paper proposes a novel zonal fault detection scheme for DCWF using the installed PSDs as fault location indicators. The proposed scheme relies on distinctive post-fault behavior of PSDs by processing the respective voltages and/or currents captured at each junction by intelligent devices (IDs) at each terminal. PSDs average currents and/or polarities of average voltages at each terminal over 0.5 ms moving window are computed for detecting the possible fault. Vertical cable faults are detected locally at bottom junctions via monitoring locality PSD voltage and core-current. Whereas, an underground cable fault tripping command is determined by a left-side ID via polarity of local horizontal PSD average voltage besides the received digital signals from right-side ID regarding horizontal and vertical PSDs voltages and sheath currents around the junction. Moreover, junction faults are also discriminated via observing peripheral sheath and local ground currents.