Comparison of fault currents in multiterminal HVDC grids with different grounding schemes

The requirements of dc circuit breakers used to protect multiterminal HVDC networks are specified by the prospective fault current. The fault current, however, strongly depends on the grounding scheme of the network. Low-ohmic and high-impedance earthing practices with different grounding points are presented and compared with each other in terms of fault currents and overvoltages during a pole-to-ground fault. To do so, monopolar and bipolar configurations of a multiterminal HVDC cable network are implemented in PSCAD and simulations are performed.