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This paper presents a time-domain equivalent circuit approach for analyzing lightning-generated electromagnetic transients in modern buildings. The building is represented by a wire-plate structure and is modeled by the internal impedance and external inductance of current cells and the coefficients of potential cells. A vector-fitting technique is applied for modeling frequency-varying internal impedance for time-domain simulation. With this unique formulation, the number of unknown variables is reduced, and computational efficiency is improved significantly. Finally, lightning-generated impulse magnetic fields and voltages within a building are evaluated. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method for calculating the resistance, inductance, and capacitance matrices of transformer windings. Importance of their precise calculation is shown in the simulation of voltage distribution over the windings for a lightning-impulse test. The results obtained in frequency domain analysis are in good agreement with the measurement data. All the parameters are calculated using the self-developed solvers, the theory and the novelty of which are described in this paper. The presented approach allows fast and accurate high-frequency modeling of transformer windings. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid method based on the transmission line modeling method (TLM) aiming to represent the soil ionization effect for grounding systems simulation. This natural phenomenon can be better represented by taking into account the variation of the conductive components present in the TLM circuit and considering the residual resistivity remaining in the soil. The proposed analytical formulation is developed with a focus on the computational implementation of the method. The model is validated by comparing synthetized test results with measured data and other numerical models (residual resistivity, TLM, and analytical model). High precision together with an easy to implement formulation indicates that the methodology presents potential for real-life applications. [ABSTRACT FROM AUTHOR]

In this paper we propose a computational procedure to simulate the magnetic behavior of inductive blocking devices for the mitigation of the induced voltage and current pulses on the aircrafts circuits during a lightning shock. The non linear and hysteretic phenomenon are simulated using a model based on the Preisach theory and implemented in a finite difference scheme in time domain. Using this procedure the performances of the blocking devices can be computed and optimized according to the standard requirements for avionic applications. A dedicated pulse generator is designed and realized for the experimental tests in order to compare numerical results and measurements. [ABSTRACT FROM AUTHOR]

This paper analyzed transient magnetic fields generated by the lightning current in the presence of 3-D conductive plates. An extended partial element equivalent circuit method was introduced to establish a network with frequency-invariant parameters for time-domain simulation. Three techniques were proposed to reduce the computational complexity in the large-plate simulation, including the analytical function of current density, the non-uniform meshing scheme, and the vector fitting technique. Numerical and experimental results were presented to validate the proposed method. Good agreements were observed. [ABSTRACT FROM AUTHOR]

This paper presents the development of an analytical formulation for estimating the potential on the soil surface, caused by electric current calculated on a grounding conductor. The formulation has a great significance in its use in conjunction with 1-D numerical methods, which are not able to determine such potentials directly. The proposed study focuses on lightning surges considering the frequency dependence of the soil properties. First, the subject is introduced emphasizing important aspects related to the analysis and representation of grounding systems against lightning. Afterward, the proposed analytical formulation is introduced with a focus on the computational implementation of the transmission line modeling method in 1-D. Simulations were carried out considering a typical horizontal electrode used as grounding in the power electric system. The formulation was validated by comparing the results with the solution based on the electromagnetic model (CDEGS Software), which is considered the most stringent for the solution of full Maxwell equations due to their minimum approaches. The results demonstrate that the generalized formulation presents good accuracy, contributing to an improved representation of grounding systems based on numerical techniques in 1-D. [ABSTRACT FROM AUTHOR]

Lightning shielding failure accounts for the highest proportion of lightning accidents for transmission systems above 500 kV. The leader propagation model (LPM) was found to be effective in the analysis of lightning shielding failure of high-voltage transmission lines, especially for the ultrahigh voltage (UHV) transmission systems. However, it was generally inefficient to calculate the shielding failure rate by LPM, since the progress of lightning development must be simulated repeatedly, which is time-consuming, and no adaptive implementation of LPM has been reported. In this paper, adaptive strategies to accelerate the computation of shielding failure analysis by LPM were proposed, which include the adaptive time step control according to the electric field at the conductor surface, non-uniform lightning current sampling based on the lightning current amplitude probability distribution, and the adaptive lightning location sampling based on recursive adaptive Simpson’s method. The analysis results were validated by the field data of the UHV transmission line in Japan, and the efficiency of the adaptive strategies was shown by the shielding failure analysis of a typical 500 kV ac transmission line. [ABSTRACT FROM AUTHOR]

The electric and magnetic fields in the vicinity of the lightning channel were measured in 2004 at the International Center for Lightning Research and Testing. In this paper, a numerical lightning channel model is presented based on the physical mechanism of lightning development. The calculation of electric and magnetic fields is divided into three stages. Before the lightning leader arrives to ground, the field is induced by the charges in the thundercloud and lightning leader. During the return stroke, the field is induced by the return stroke current and the remainder charges in lightning channel and thundercloud. After the return stroke, the field is induced by the remainder thundercloud charges. The electric and magnetic fields are calculated by means of the image method and calculated fields are compared with those measured. [ABSTRACT FROM PUBLISHER]

In this paper, a new non-uniform multiconductor transmission line model combining with lumped circuit elements for a composite transmission line (TL) tower under lightning strokes is established. The metal ground-wire cross arms, the metal tower main body and its bracings are modeled as equivalent horizontal and vertical TLs, respectively. The two grounding ladders are regarded as two parallel–vertical TLs considering their mutual coupling. These distributed TL parameters are calculated by analytic equations. The composite arms are equivalent as lumped capacitances determined by employing 3-D finite-element method. The lightning overvoltage analysis for a 330-kV composite tower is performed by applying the hybrid model. The incident and reflected voltages are calculated. The insulation performance evaluation for the composite tower is discussed in detail. [ABSTRACT FROM PUBLISHER]

The grounding system is very important for lightning protection. If the lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. In this paper, an efficient time domain method is proposed to analyze the transient performance of the grounding system. The method takes account of nonlinear soil ionization, the shielding effect among electrodes, and frequency-dependent parameters all together. First, a frequency domain circuit model is set up based on a moment method coupling with circuit theory. Then, the model is approximated by a frequency-independent circuit model with the help of vector fitting method. Finally, the time-varying soil ionization is considered by making corresponding parameters time-varying when a time domain method is used to solve the circuit model. The method is validated by field test. [ABSTRACT FROM AUTHOR]

Saturated Core High Temperature Superconducting (HTS) Fault Current Limiter (FCL) is one kind of limiters that can work effectively on short-circuit current limitation. In this paper, an equivalent circuit model depending on ac coil of HTS FCL is built for voltage distribution analysis under transient overvoltage. The equivalent circuit components, such as the capacitances and inductances, are calculated by using finite element method. The voltage distribution and oscillation analysis of ac coil may benefit to the insulation design of HTS FCL. [ABSTRACT FROM AUTHOR]

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]

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]

Electromagnetic interference (EMI) on secondary dc cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order to reduce EMI, the cable shield is generally connected to the grounding grid at both ends. Ground potential difference between two grounding points of the cable shield can be high due to high impedance of the grounding grid at high frequencies. In this paper, we present a hybrid method to analyze this complex system. As a result, both the current flowing in the cable shield and the transverse voltage between the cable core and shield are calculated. Compared with the measured results, the proposed method is demonstrated to be correct and effective. [ABSTRACT FROM AUTHOR]