Influence of Building Structures on the Lightning Return Stroke Current

This paper addresses the influence of building structures on the lightning return stroke current. An equivalent circuit model of the lightning channel is set up using the coupled pi-type circuit. This model is then integrated with the building structure via the lightning attachment and the mutual coupling. With this integrated circuit model, the lightning current in the building is evaluated using EMTP. It is found that the building generally behaves like a transmission line at its rooftop and on the ground. The rooftop current is the result of the incident lightning current and its subsequent reflected currents on the ground. The propagation parameters of the building can be determined numerically using the integrated model. These parameters vary with the structure type, size, and others. In general, the impedance of typical buildings lies between the channel impedance and grounding impedance, and the lightning current on the lower floors is higher. It is also found that excluding the mutual coupling in the integrated circuit model alters the waveform of the lightning current.