A lightning strike in a neighborhood can induce significant currents in tall down conductors. Although the magnitude of current in this case is much smaller than that encountered during a direct strike, the probability of occurrence and the frequency content is higher. In view of this, appropriate knowledge of the characteristics of such induced currents is relevant for the scrutinization of the recorded currents. Considering these, the present paper makes a preliminary investigation into the basic characteristics of lightning-induced currents in simple tall vertical down conductors. The electromagnetic model is employed for the study, and NEC-2 is employed for the numerical field computations. Laboratory experiments with reduced-scale electromagnetic model of the system are employed to validate the numerical approach. The influence of important parameters has been investigated and highly insightful results obtained. The induced current is found to depend on the maximum rate of rise of the stroke current and its velocity of propagation, the height of the down conductor, and the footing impedance. The channel inclination and the distance between the channel and the down conductor have significant influence on the magnitude of the induced current. It is found that the radius of the down conductor is not very influential. The induced current due to a stroke on a nearby conducting object of considerable height can have different overall features.
In this paper, a study is carried out to determine the magnitude and nature of the induced currents in the steel structure of a steel reinforced concrete building due to a nearby lightning strike to ground. The influence of various parameters of steel geometry of a building on the induced currents is investigated. Electromagnetic model is employed for the study and numerical electromagnetic code 2 is used for the numerical field computations. The time-domain quantities are obtained using appropriate Fourier and inverse Fourier transform techniques in MATLAB. It is observed that the height of the building and increased number of rods in the columns and beams have an effect to increase the peak value of the induced currents. It is also observed that the roof in the building has the shielding effect to reduce the peak value of the induced current. The diameters of the rods and material used have no significant influence on the magnitude and nature of the induced currents.
In the present work a study is carried out to determine the magnitude and nature of the induced current in the steel of a steel reinforced concrete building due to a nearby lightning stroke to ground and strike to nearby elevated objects. A comparison of the two is presented. For the study, buildings of three different heights with number of floors are considered. The vertical down conductor of different heights is considered as nearby elevated object. Lightning channel of length 1 km is employed. Two velocities of propagation of channel current, one equal to velocity of light and another of 1/3 of velocity of light are considered. A current source model for the source is employed for the study. Electromagnetic model is employed and Numerical Electromagnetic Code-2 (NEC-2) is used for the numerical field computations. It is found that when lightning strikes the elevated object which is nearby to the building, induces more currents in steel parts of the building rather than the current due to nearby strike to ground. The height of the elevated object also has significant effect on the magnitude of the induced current.
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