To protect the insulation cable and to enable the leakage current from the external conductor to be discharged to the ground as the external conductor is in contact with the ground of the cut hole or the cut ditch through the semiconductor layer.

The ground system comprises a lightning arrester rod installed on a supporting body 6 in insulated state and an insulation cable comprising a center conductor 2 connected with the lightning arrester rod and acts at least as a grounding pole, an insulation layer 3 at the outer periphery of the center conductor, an external conductor 4 acting as a shield layer grounding pole, and a semiconductor layer 5. The other end of the insulation cable connected with the lightning arrester rod is buried in the cut hole 8 or a cut ditch 11 formed in the ground through a resistor body 9, and the center conductor as a grounding pole and the external conductor as the shield layer grounding pole installed via the insulation layer are installed keeping a sufficient insulation distance.