Validation of the Simpson-finite-difference time domain method for evaluating the electromagnetic field in the vicinity of the lightning channel initiated at ground level (original) (raw)
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Progress In …, 2010
Evaluation of electric and magnetic fields due to lightning discharge is important in determination of lightning induced voltage and power system protection especially to the distribution system. In this paper, by using dipole method, Maxwell equations and second order finite-difference time domain (later referred as a 2nd FDTD method) on two realistic return stroke currents, an algorithm for evaluation of electric fields is proposed, which is based on numerical methods in the time domain. Besides proving greater accuracy, it also allows the evaluation of electric and magnetic fields away from lightning channel. In addition, the comparison between simulation results and measured fields' wave shape showed that the proposed algorithm is in good agreement for evaluation of electric and magnetic fields due to lightning channel.
Journal of Electrostatics, 2008
We present an analysis of the electromagnetic fields at very close range from a tower struck by lightning. The electromagnetic fields are evaluated for observation points above, on the surface and below the ground plane characterized by a finite conductivity. The computations are obtained using the Finite-Difference Time-Domain (FDTD) technique, in which the so-called engineering models are incorporated to represent the spatial-temporal distribution of the current along the channel and along the strike object. The approach is tested using a set of simultaneously recorded data published in the literature consisting of the current measured at the top of the Peissenberg tower and the associated electric and magnetic fields and very good agreement has been found. Simulation results are performed for an observation point located 50 m from the base of the channel (or tower, when present) and for three cases, namely (i) a lightning strike to ground, and (ii) a lightning strike to a 168-m tall tower, and (iii) a lightning strike to a 553-m tall tower. The effect of the presence of the tower and the effect of finite ground conductivity on the generated above-ground and underground electromagnetic fields are illustrated and discussed. It is shown that the underground electric fields are markedly affected by the ground conductivity. The underground electric field is predominantly horizontal with a negative polarity. The vertical electric field component is characterized by a bipolar wave-shape. The ground conductivity affects in a lesser degree the magnetic field penetrating into the ground. Above the ground and on the ground surface, the vertical electric field and the azimuthal magnetic field generated by a lightning return stroke initiated at ground level are nearly insensitive to the height of the observation point above ground. For the considered distance range (50 m), they can be computed assuming the ground as a perfectly conducting plane. The magnetic field above ground at such close distance is virtually not affected by the ground conductivity. The presence of a tower results in a significant decrease of the vertical electric field in the immediate vicinity of the tower. Unlike the case of a ground-initiated return stroke, the above-ground vertical electric field associated with a return stroke to tall tower is very much affected by the ground conductivity. Depending on the value of this latter, this component could exhibit an inversion of polarity.
Progress In Electromagnetics …, 2011
Evaluation of electromagnetic fields caused by the lightning channel is an appealing topic in order to consider the indirect effects of lightning on the power lines. A common assumption for the calculation of electromagnetic fields at the observation point is a vertical lightning channel, but the fact is that in reality the lightning channel is seldom vertical on the ground surface. In this study, the electromagnetic fields due to inclined lightning channel at various observation points with different angles and with respect to the image of lightning channel on the ground surface were explored. This study also proposes general equations that can estimate the electric fields due to inclined lightning channel through the 2nd FDTD method. The proposed method supports the notion of vertical lightning channel while the channel angle with respect to z-axis is assumed to be zero. This method was validated through the data gathered from five fields: three at a close distance from inclined lightning channel and two at intermediate distances from vertical lightning channel. Similarly, due to inclined lightning channel, the effects of geometrical and current parameters on the electromagnetic fields are considered. This study substantiates different coupling models with FDTD structure directly at the time domain without a need for extra converters.