Combining Earth-Leakage and Short-Circuit Protection in DC Grids

In an AC grid, earth-leakage and over-current protection is realized by electromechanical devices. In a DC grid, electronic protection is to be applied, because of arcing in mechanical separators. The power flow in a DC grid is regulated using power electronic converters. The combination of the electronic protection and the converters used in a DC grid, reduces the overall component count in a DC grid. Furthermore, the power electronic converters in a DC grid, need electronic protection as well. In this paper the location of the electronic protection in a DC grid and the combination of the electronic protection and the converters is elaborated. The combination of earth-leakage, arc, over-current and short-circuit protection, as well as inrush methods, into the Interlink and Grid Manager power electronic converters is detailed in this paper. A typical design of an Flux-gate for earth-leakage detection and experimental results on short-circuit detection are given in the paper.