Because the recursion-based method only requires the evaluation of the most recent voltage history data (versus the entire history in a "brute-force" convolution evaluation), we achieve necessary time speed- ups across a variety of TL/Earth geometry/material scenarios.
Addressing this to facilitate practical simulation of EMP excitation of TLs, we first apply a technique more » to extract an (approximate) complex exponential function basis-fit to the ground/Earth's impedance function, followed by incorporating this into a recursion-based convolution acceleration technique.
This is because the method requires a temporal convolution to account for the losses in the ground. In a time- domain, transmission line (TL) model implementation, predictions are computationally bottlenecked time-wise, either for late-time predictions (about 100ns-10000ns range) or predictions concerning EMP excitation of long TLs (order of kilometers or more ). In this report we overview the fundamental concepts for a pair of techniques which together greatly hasten computational predictions of electromagnetic pulse (EMP) excitation of finite-length dissipative conductors over a ground plane. For typical high-voltage power line load impedances, it is shown that voltage magnitudes in the MV range can be induced across the line termination, in the case of a wave with a near-grazing incidence angle and with wave vector aligned along the horizontal conductor. The application to the threat analysis of a high-altitude electromagnetic pulse impact on a power transmission line is discussed by considering the time-domain solution (via inverse Fourier transform) for an incident EMP fast-rise transient (E1) waveshape, following the standard IEC specifications. A frequency-domain Thévenin equivalent model is developed to relate the incident wave amplitude to more » the voltage across a generic load, connected at any point on the vertical conductor. Calculating the scattering matrix for one rotation sample in CST MWS takes about 40 min implying a speed up factor compared to the novel method of about 460. This configuration corresponds to the worst-case wave coupling, because it leads to a line induced current larger than in the cases of finite and multiconductor lines. The model is developed using a semi-infinitely long single conductor above a lossy ground plane and connected by an arbitrary load impedance to a vertical grounding conductor. A simple model for coupling of an electromagnetic plane wave incident on a conductor above ground has been developed using reciprocity theory, providing some advantages as compared to the conventional transmission line approach.