Hailin Chen

The breakdown current, current impulse velocity, and E-field in air gap discharge are of interest among researchers on high-voltage engineering and lightning study. It is the breakdown current and current impulse velocity that govern the radiated E-field property. The current impulse velocity, however, is not well addressed in the literature. In this paper, we use a self-developed high-speed observation system, a Rogowski coil, and a transient E-field sensor to measure the current impulse propagation velocity, breakdown current, and vertical E-field in the rod-to-plane discharge after the air gap breakdown under dc voltage. From the time difference of arrival of light signals in different receiving channels, the resultant current impulse propagation velocity is measured as 6.81 ± 0.57 × 106 m/s. Meanwhile, the breakdown current at the bottom of the grounded rod electrode has a peak value of approximately 1.3 kA and 10%–90% rise time of 40 ns, and the transient vertical E-field at ground level has an amplitude of approximately 15 kV/m and 10%–90% rise time of 64 ns. In addition, according to the measured breakdown current and resultant current impulse velocity, the vertical E-field is computed by using the finite-difference time-domain method in the two-dimensional cylindrical coordinate system. The computed vertical E-field agrees well with the measured E-field, validating our measured current impulse velocity. Besides, the computed horizontal E-field and azimuthal H-field are also analyzed. Finally, the influence of current impulse velocity on the vertical and horizontal E-field and azimuthal H-field is discussed.

For high efficient analysis of an obliquely incident plane wave on periodic structures, one-step leapfrog locally one-dimensional finite-difference time-domain (LOD-FDTD) method is proposed in this letter. Firstly, by applying the LOD scheme into the improved split-field algorithm, unconditional stability can be achieved. And then, by introducing three auxiliary variables, the one-step leapfrog implementation for the LOD scheme is derived. Finally, the implementation of the convolutional perfectly matched layer (CPML) for the proposed method is derived. At last, numerical results are given to verify the accuracy and efficiency of the proposed method.

A memory-efficient formulation with the uniaxial anisotropic perfectly matched layer (UPML) absorbing boundary condition (ABC) is presented for the unconditionally stable FDTD method combined with weighted Laguerre polynomials (WLP). The divergence theorem is applied to the UPML absorber. This leads to a memory-efficient matrix equation. The validity of the proposed method is shown through a numerical example of scattering from a two dimensional (2-D) rectangular conductor.

The ADI-BOR-FDTD method has been proposed to simulate the transient solutions of electromagnetic wave propagation in structures with circular symmetry. It inherits the advantages of both ADI-FDTD and BOR-FDTD methods, with a memory reduction to cylindrical ADI-FDTD and no CFL condition restraint. In this paper, the Schur-Cohn-Fujiwa criterion was used to analysis the stability of this method.

In this letter, a memory efficient modification to the unconditionally stable finite-difference time-domain (FDTD) method combined with weighted Laguerre polynomials (WLP) is proposed. The divergence theorem is applied to the lossy media and perfectly matched layer (PML). This leads to a more memory-efficient matrix equation, and the computation time is reduced. A numerical example considering a two dimensional (2-D) TE case is presented to demonstrate the efficiency of the proposed algorithm.