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In this paper, based on the moment method and the circuit theory, an approach is proposed to analyze the current distribution and the electromagnetic field of a building struck by lightning. By introducing the concept of complex resistivity in the air and the soil, the approach can consider the metallic grids under the ground and above the ground altogether. Both the potential differences among the grounding parts and the electromagnetic interactions among the grids are taken into account. It shows that the resistivity of soil will affect the electromagnetic field greatly. When the electromagnetic fields around buildings near the lightning struck point are investigated, or when a building has a separated grounding system, the effect of the grounding systems must be considered. [ABSTRACT FROM AUTHOR]

In order to analyze the lightning transient of a thinwire system, a time-domain method of reducing the thin-wire conductor system into an equivalent active multiport network based on the partial-element electric-circuit model is presented in this paper. A modified-mesh-current (MMC) approach is developed, uses node charge and mesh current as its variables, and takes into account both capacitive coupling and inductive coupling among conductors. Equations given by MMC are expressed in a statespace form. These equations are reduced to an active multiport network model using the trapezoidal scheme. The active multiport network is described by a constant-input-conductance matrix and a vector of currents that are updated using passed values. The multiport network can easily interface with linear and nonlinear components in an electromagnetic transient program. Since the proposed method requires only one-time calculation of the inverse of the system matrix, it is more efficient in comparison to the conventional full-wave method in the frequency domain. For a large system, well-established model-order-reduction techniques can be applied to the MMC formulation to reduce it to a small scale one. The proposed method is validated by comparing its results with NEC-calculated ones and published field measurements. Finally, the method is used to simulate two lightning-strike scenarios. [ABSTRACT FROM AUTHOR]

When lightning strikes a substation or a transmission tower near the substation, high current generated by the stroke would flow into the grounding grid of the substation and dissipate in the soil. The transient characteristic of the grounding grid is very important to the safe and reliable operation of the power system. A circuit model with a lumped time-variable parameter is proposed to calculate the transient characteristics of a grounding grid under lightning current. The ionization phenomena around the ground conductors in the soil are simulated by means of time-variable parameters under appropriate conditions. The influences of different parameters on the transient characteristics of the grounding grid subjected to lightning impulse current are analyzed and the effective usage area of the grounding grid under lightning is discussed. [ABSTRACT FROM AUTHOR]

In this paper, a simulation model is proposed to evaluate the electromagnetic transient surge current distribution in a lightning protection system (LPS) due to a direct lightning stroke. The model is based on the coupled transmission line network in the frequency domain combined with the Fourier transform technique. The conductor of the LPS is described using the coupled transmission line model, and can be reduced to an active two-port equivalent circuit. The unknown quantities are the node voltages of the LPS at the physical junction, which leads to a fast solver at each frequency. The validation of the proposed approach is performed by comparing the results with those in the technical literature. The numerical examples show the flexibility, efficiency, and accuracy of the model in the range of practical application of LPS. [ABSTRACT FROM AUTHOR]

This paper presents the study of a long electric arc in free air due to lightning stroke on the parallel gap lightning protection device (PGLPD) on high-voltage overhead transmission lines. Based on the latest electric arc model, the analysis method of the magnetic field generated by the current flowing through the PGLPD, electric arc, transmission lines, steel tower, and ground wires is developed, and the movement process of the long arc along the surface of the insulator strings is simulated. The simulation results are in agreement with the experimental results. The study is very helpful for the optimal design and suitable assemblage of the PGLPD. [ABSTRACT FROM AUTHOR]

The grounding systems are simply handled as lumped resistances with constant values in traditional lightning transient analysis of substation. A complete transmission line model is proposed to consider the actual transient process of power network and the grounding grid of the substation and the grounding devices of transmission towers. A loss transmission line model with time-variable parameters is proposed to calculate the transient characteristics of grounding systems under lightning current in which the soil ionization phenomena around the ground conductors are considered. The analyzed results by the proposed model have large differences with those obtained by the traditional simplified method. The transient characteristics of grounding systems have strong influence on the lightning transient process of substation. [ABSTRACT FROM AUTHOR]

In a high soil resistivity area, counterpoise wires are applied to decrease the grounding resistance of tower grounding devices. If the conductor of counterpoise wire is very long, although the power frequency grounding resistance of the tower grounding device ii decreased, the lightning protection performance of the transmission line is still not good. The influences of the length of grounding electrodes on the lightning transient characteristic were analyzed. The dynamic and nonlinear effect of soil ionization around the grounding electrode was considered in the analysis model of transient characteristics for the grounding electrodes under lightning impulse. The counterpoise wire has an effective length when lightning passes through it. When the length of a grounding electrode exceeds the effective length, the grounding conductor will not be utilized effectively. The simulating experiments were performed to analyze influences of the length of the counterpoise wire on the impulse characteristics. The formulae to calculate the impulse effective lengths of counterpoise wires were proposed. The model proposed in the paper has been validated by comparing the numerical results with experimental tests. [ABSTRACT FROM AUTHOR]

The electromagnetic environments (EMEs) of the planned Zhongguancun Software Park near transmission lines, including electrical field, magnetic field, and ground potential rise under three cases of lightning stroke, normal operation, and short-circuit faults, are assessed by numerical analysis. The power frequency EMEs of the software park are below the maximum ecological allowed exposure values for the general public; , nevertheless, the power frequency magnetic field may interfere with the sensitive computer display unit. The influence of short-circuit fault in two different cases of remote short circuit and neighboring short circuit on the software park is discussed. The main problem we must pay attention to is the ground potential rise in the software park due to neighboring short-circuit fault; it would threaten the safe operation of electronic devices in the software park. On the other hand, the lightning stroke is a serious threat to the software park. How to improve the EMEs of the software park is discussed. [ABSTRACT FROM AUTHOR]