Study On The Performance Of Lightning Rod Considering The Effect Of Induced Charge

Lightning is a common natural disaster, it has brought enormous damage to human society. In order to prevent from lightning’s damage, people have taken some lightning protection measures. Of all the measures, lightning rod is the most simple and the most commonly used to protect people from direct lightning. However, it is found that the buildings which are in the protection area of lightning rod are sometimes stroken by lightning. It’s a problem that people have to pay some attention to improve the performance of lightning rod.Aiming at this fact that lightning rod happens to shield failure, this paper puts out a surpose that the lightning protection performance of lightning rod is affected by the surrounding buildings. Whether a rod could attract the lightning or not is decided on the competition between the Coulomb force of lightning rod and the buildings to the lightning leader. Therefore, the author has searched on the characteristic of a lightning rod especially considering on the space electric field generated by the induced charge. In order to calculate the amount of induced charge, first of all, the author has estabished a two-dimensional model of the lightning leader, and then make out the induced charge of the buildings and lightning rod and deduce the calculation formula for the space electric field and potential as well. And base on these work, according to the leader progation theory, a physical model of leader connection process in lightning discharge is put forward. Then use the Maxwell, an electromagnetic field finite element simulation software to simulate the connection process of the lightning leader and the objects on the earth. According to the simulation results under the conditions of such as building with different sizes, down leader with different potential, rod with different height and in different position of building’s top, to analysis the effects of all these factor to the lightning performance of air terminal. Finally, a long air gap discharge experiment is taken to evaluate the lightning protection performance of a blunt rod and plate rod. It’s found from the experiment that the head shape of lightning rod and the grounding resistance of lightning rod also has influence on the performance of lightning rod.Some main conclusions are made at last, these are:First, the height of lightning rod has effect on lightning protection performance of air terminal, when the building is not too tall, the effiency of air terminal is improved with its height increasing, while it seems to be no difference when the building is so high. Second, the corners of buildings also have the ability to attract the lightning, so it is suggested that we take some particular measures to protect the parts of buildings such as corners and where these are convex. Third, the lightning protection performance of plate rod is better than blunt rod, so the head shape of lightning rod remains to be optimized.