A Comparative Study on Induced Currents in Steel Reinforced Building Due to a Nearby Lightning Strike to Ground and a Strike to Nearby Elevated Object (original) (raw)
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IEEE Transactions on Power Delivery, 2002
Lightning triggered from natural thunderclouds using the rocket-and-wire technique was employed in order to subject to direct lightning strikes the lightning protective system of a test house at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, FL. The electrical circuit of the test house was connected to the secondary of a padmount distribution transformer located a distance of about 50 m from the house. The transformer primary was connected to a 650-m long unenergized underground power cable. The test house had two ground rods, one for the lightning protective system grounding and the other for the power supply system grounding. The two rods were about 3 m apart and were connected by a metallic cable. Lightning current was injected into the lightning protective system ground rod, and the currents and voltages at different points in the test system were measured. The waveshapes of currents in the ground rods of the test house differed markedly from the current waveshapes in other parts of the overall system. The ground rods at the test house appeared to filter out the higher frequency components of the lightning current, allowing the lower frequency components of the current to enter the house's electrical circuit, that is, the ground rods appeared to exhibit a capacitive behavior rather than the often expected resistive behavior. This effect was observed for dc grounding resistances of the rods (driven in sandy soil with conductivity of about 2 5 10 4 S/m) ranging from more than a thousand ohms to some tens of ohms. The peak values of 1) the current entering the test house's electrical circuit, 2) the current flowing to the distribution transformer secondary neutral, and 3) the current flowing through the surge protective devices at the test house's service entrance were observed to be greater than in either of the two scenarios suggested by the International Electrotechnical Commission.
This paper presents an analysis of lightning return strokes to tall structures. The interaction of lightning with a tall structure is modeled using the antenna theory. The finite ground conductivity as well as the buried grounding system of the tall structure are taken into account in the analysis. It is shown that the current waveform, in sections of the tower close to ground, is somewhat affected by a finite ground conductivity. However, for sections further up the tower, it is not significantly influenced. Furthermore, our simulations show that some fine structure associated with current waveforms measured on the Toronto CN Tower can be attributed to the finite ground conductivity. It is also shown that the current path down the tower structure is notably subjected to the skin effect. The current distribution along the buried grounding structure of the tower is also presented, illustrating the dispersion effect as a function of the ground conductivity. Finally, the lightning return-stroke generated electric and magnetic fields computed at a distance of 2 km from the tower are presented. It is shown that some late-time subsidiary peaks are smoothed out by the effect of the propagation along a finitely-conducting ground.
IEEE Transactions on Power Delivery, 2000
We present the results of structural lightning protective system (LPS) tests conducted in 2004 and 2005 at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, FL. Lightning was triggered using the rocket-andwire technique, and its current was directly injected into the LPS. The test configurations in 2004 and 2005 differed in the lightning current injection point, number of down conductors, grounding system at the test house, and the use of surge protective devices.
Journal of Electrostatics, 2004
In IEC 61312-2 equations for the assessment of the magnetic fields inside structures due to a direct lightning strike are given. These equations are based on computer simulations for shields consisting of a single-layer steel grid of a given mesh width. Real constructions, however, contain at least two layers of reinforcement steel grids. The objective of this study was to experimentally determine the additional shielding effectiveness of a second reinforcement layer compared to a single-layer grid. To this end, simulated structures were set up in the high current laboratory. The structures consisted of cubic cages of 2 m side length with one or with two reinforcement grids, respectively. The structures were exposed to direct lightning currents representing the variety of anticipated lightning current waveforms. The magnetic fields and their derivatives at several positions inside the structure as well as the voltage between "floor" and "roof" in the center were determined for different current injection points. From these data the improvement of the shielding caused by a second reinforcement layer is derived.