Role of Steel Frames of Buildings for Mitigation of Lightning-Induced Magnetic Fields

Induced magnetic fields inside of a directly stricken building by lightning may cause faults, malfunctions, or data loss in electronic systems. In IEC 62305-4, the space to be protected is divided into several levels of lightning protection zones (LPZs). Steel frames of a building form a lightning protection system (LPS), and the space inside of it is LPZ1. LPZ1 is defined as the space where lightning cannot enter directly and the electric and magnetic fields inside of it can be reduced. In this paper, the contribution of lightning current in each part of the steel frames to the induced magnetic fields is discussed. Furthermore, a measure for a rational design of LPS is proposed aiming at further reduction of the induced magnetic fields inside of it.