Effect Of Tall Towers On The Lightning Return Stroke Current And Its Electromagnetic Field

Tall towers,skyscraper and other tall buildings are easily struck by lightning, because tall buildings can easily produce an upward leader when a thunderstorm passing by, and some towers can be struck tens of times annually. At the same time, Experts at home and broad generally measure nature lightning current on tall towers and do research on lightning discharge physics mechanism and so on. But as the major groups that struck by lightning, the research on the current and electromagnetic field associated with lightning-return strokes to tall towers are a fat lot in china. In this paper we numerical calculated the space-time distributing of current lightning-return strokes to tall towers, and come to conclusions as follow:1. The current peak value and maximum steepness at the bottom of the tower are 30% to 50% larger than those associated with the injected current. So the SPD used in the tower must be have a better parameter, the rated discharge current and maximum discharge current should be increase; The duration of peak value of the return current in the tower is longer; this takes an increase of energy by 10% to 82%. So the 'let energy' of SPD used in the tower should increase 82%; The current derivative at the bottom of the tower increase most obvious; the subsequent current are more significantly affected by the presence of the tower, increased by 50%,this make the lightning energy increase by82%.2.The appearance of towers increase the electromagnetic field significantly, the electromagnetic field can enhance 1-3times within the range in decades kilometers, the result worth paying attention to especially to lightning protection project; The results show that at close distances (100 m-10 km), the ratio of EF (electric field) peaks at any two azimuths is within 0.8-2.3; With the increase of distance, the dependence on azimuth weakens. However, the dependence of MF (magnetic field) waveforms on azimuth is obvious, and the ratio of MF peaks at any two azimuths ranges about from 2 to 4.4. The attenuation of electromagnetic field produced by lightning strokes to tall towers transmit on seawater,wetland,dry land and lake water four kinds of surface is respectively 98.2%,85.3%,73.3%,57.2%。...