Investigation of Transient Induced Voltages due to Lightning in An Intelligent Building

Abstract

Transient induced voltages due to lightning in an intelligent building are simulated using the generalized circuit analysis program EMTP based on a conventional circuit theory. A calculated result agrees satisfactorily with an experimental result, and thus the calculation method is proved to be applicable to an analysis of transient induced voltages. Using the method, transient voltages and currents in an intelligent building, which behaves as an inducing circuit are evaluated. It is observed that the size of the steel frame, a grounding resistance and a lightning current waveform affect significantly the voltages and currents. Also, it is found that a lightning current flowing into the building structure produces a voltage difference between different points on the same floor. A transient induced voltage across a resistance of a square-shape closed loop is basically determined by the rise time of a lightning current, the size of the loop and a separation distance from the vertical conductor which carries the largest lightning current. The maximum induced voltage to an 1×1m loop is observed to be 11V across 50 Ω resistance when the applied lightning current is of 1kA amplitude and 1/40μs waveshape. If a 10kA lightning, the average current measured, hits a building, the induced voltage reaches 100V which may cause a trouble on digital/electronic equipments.