Evaluation for the Lightning Overvoltage at the Distribution Boards of a Building Using Steel Frames Grounding System

In steel-framed buildings, the steel framework is occasionally used as a ground line for electric shock protection to reduce the cost of wiring equipment. When such a building is struck by lightning, lightning overvoltage is generated in the distribution boards on each floor owing to electromagnetic induction caused by the current flowing in the building structure. When steel frames are used as ground lines, measures such as the electromagnetic shielding of wiring and minimization of wiring loops to suppress lightning overvoltages are difficult to implement. In this study, a method for evaluating lightning overvoltages in buildings using steel frames as ground lines was developed, and measures to suppress overvoltages were examined. Installing electric pipe shafts (EPSs) for the power lines in the center of the building was proved to be effective.