Improved ground fault handling in power distribution systems with mixed underground and aerial power lines

The present invention relates to a a power transmission and/or distribution system (10) comprising a power grid (G), a first power transmission section (12) and a ground fault handling device (GHR) for connecting the grid to the first section, where the first section (12) is of a first type including at least one underground power line. The ground fault handling device comprises a first isolating transformer (IT1) having a first set of windings and a second set of windings, where the first set is coupled to the gird, the second set is coupled to the first section and the windings of the second set are solidly or resistively (R1, R3, R4, R5) grounded. There is also at least one grounding transformer (GT1, GT2, GT3) shunt connected between an isolating transformer of a ground fault handling device and a power transmission section.