Reduction Effect of Induced Magnetic Field in Building by using High-voltage Cable-type Down-conductor

Abstract

Special facilities such as data centers, computer centers, and hospitals with operating rooms require an extremely static electromagnetic environment. In this study, we investigated the effectiveness of an isolated type down-conductor for reduction of the magnetic field inside the building due to lightning strikes by using electromagnetic field analysis. We analyzed the four cases of the down-conductors such as building structures, bare wires, and two types of high-voltage insulated-cables which is sheath opened type and sheath shorted type. Using bare wires and sheath opened cable-type down-conductors, the internal magnetic field of the building reduced. This is because the lightning current flows in the opposite direction in the building structural pillars close to the down-conductors, and it cancel the internal magnetic fields. Comparing the bear conductor and the sheath opened cable-type conductor from the viewpoint of the overvoltage to the building structure, the overvoltage became smaller as the cace of using the cable-type duwn-conductor.