Circulating Net Currents in Meshed DC Distribution Grids: A Challenge for Residual Ground Fault Protection

In dc distribution grids, residual ground current protection is more feasible than in ac distribution grids, where stray capacitance leads to significant ac ground currents. However, when meshing dc distribution grids, circulating net currents can appear that resemble residual ground currents and would trip traditional protection schemes. This letter introduces this phenomenon in both unipolar and bipolar dc distribution grids. Furthermore, worst case net current magnitudes are derived and examples are shown. Implications for measurement and protection devices are discussed.