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

The present invention relates to a ground fault handling device (GHR) that provides an interface between two power transmission sections of a power transmission and/or distribution system as well as to such a power transmission and/or distribution system (10). The system comprises a first and a second power transmission section (G, 12) and the ground fault handling device (GHR) for connecting the first section to the second section, where the second section (12) is of a first type including at least one underground power line and the first section (G) is of another type lacking underground power lines. 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 first section, the second set is coupled to the second section and the windings of the second set are solidly or resistively (R1, R3, R4, R5) grounded.