静電シールド - 架空地ワイヤ避雷

Static shield is part of a grounding cable strung above the power and data lines. When lightning strikes, the overhead ground wires redirect that energy along their cores, then send the strike into the ground. This grounding method keeps the electricity from causing damage to the rest of the electrical equipment.

Overhead ground wires for protection of overhead power lines span the distance between support towers. They run above power and data transmission lines, and they are grounded at regular intervals. Current travels differently on static wire than it does through data and power lines. However, OHGW's primary purpose is intercepting lightning strikes before that electricity reaches the transmission lines below. Ground wire manufacturers use steel alloys to produce these elements, as static wires only carry current when struck by lightning. 

That interference protects the power and data lines. This protection is so important that most modern systems have two overhead ground wires instead of a single static wire. 

Once the current is traveling along the static wire, it looks for the nearest place it can discharge energy. The overhead ground wire carries the current to the next tower, where the grounding guides the lightning discharge energy into the earth.

Several factors can affect the way an overhead ground wire works. One of the most common complications is soil resistivity. When the footing resistance (between the tower foot and the earth) is high, the current cannot enter the ground. To discharge the building energy, the current completes a back flashover. Preventing back flashovers involves lowering tower foot resistance with counterpoises and driven rods.

Note that overhead shield wire has no impact on switching surges.