The current induced on an infinite multiple conductor transmission line located above a lossy homogeneous medium due to a transient plane wave is discussed. An exact solution is formulated in the frequency domain using a spatial transform technique. The widely utilized quasi-TEM approximation is derived directly from the exact solution with emphasis on the physical consequences of the assumptions made. Both frequency domain and time domain numerical results are presented for typical transmission structures and documented electromagnetic pulse (EMP) excitations. Comparison of the quasi-TEM approximation to the exact solution is made in order to study the validity of its application in EMP coupling problems. The modeling of the EMP source as an incident plane wave is examined by comparing the induced current due to a dipole source with its steepest-descent contribution. >

Plane wave coupling to multiple conductor transmission lines above a lossy earth

Preface 1. What is lightning? 2. Lightning damage 3. General methods for lightning protection: Faraday cages, topological shields and more practical approaches: cone of protection and rolling sphere methods 4. Structure protection: air terminals and down conductors 5. Structure protection: grounding 6. Surge protection for electronics in low-voltage electrical systems 7. Humans and animals 8. Lightning warning 9. Airships, airplanes, and launch vehicles 10. Ships and boats 11. Trees 12. Overhead and underground power and communication lines 13. Lightning elimination 14. So, what do we know and what don't we know about lightning protection? References Index.

http://www.gbv.de/dms/ilmenau/toc/563314621.PDF

The Art and Science of Lightning Protection

Since the 1960s significant effort has gone into developing requisite technology for the nuclear electromagnetic pulse (EMP). In the late 1970s several important summary documents were published. The author updates this information to the present. It is noted that EMP has affected a set of related areas which can be collectively referred to as high-power electromagnetics (HPE). This includes direct-strike lightning, high-power microwaves (HPM), and some aspects of transient radar. >

From the electromagnetic pulse to high-power electromagnetics

Capacitive Power Transfer (CPT) technology has been proposed and investigated recently as an alternative contactless power transfer method which has the advantages of being able to transfer power across metal barriers and causing low power losses in metal surrounding circumstances However, more fundamental researches are needed to guide CPT coupling analysis and design Based on the Duality Principle, this paper proposes a generalized coupling model to describe the electric field coupling between the primary and secondary side of CPT systems The concept of mutual capacitance is extended in a CPT system to decouple the primary and secondary circuits A new term capacitive coupling factor is introduced to provide a direct comparison for different coupling design The coupling model for multiple pickups is also developed A CPT prototype has been built and the experimental results have shown that the new model can be used to improve the circuit tuning for significant output power increase

A generalized coupling model for Capacitive Power Transfer systems

Low-frequency (quasi-static) electromagnetic penetration of an aperture can be reduced by loading the aperture with a conductive film or a bonded-junction wire mesh. A quantitative analysis of this phenomenon is carried out in this paper for a loaded circular aperture in a perfectly conducting ground plane of infinite transverse extent. Contact resistance between the aperture loading and the rim is taken into account. The quasi-static magnetic-field problem and the electrostatic field problem from which the aperture polarizabilities and penetrant fluxes are determined are shown to reduce to the problem of solving a single Fredholm integral equation. Exact (numerical) and approximate (variational) solutions to this integral equation are obtained, and the latter are used to represent the polarizabilities and penetrant fluxes by simple analytical formulas and equivalent circuits. These representations are found to be quite accurate when the contact resistance is not too large

Low-Frequency Electromagnetic Penetration of Loaded Apertures

An analysis of the shielding effectiveness of braidedwire shields is made using the parameters of the woven wire and the theory of electromagnetic coupling through small irises. The coupling through the rhombic-shaped holes in the braid is approximated by using the electric and magnetic polarizabilities of elliptical holes of the same width and length as the rhombus. The analysis develops the transfer impedance and the mutual capacitance of the shield. The transfer impedance is calculated and plotted for shields of different optical coverages. The variation of mutual capacitance and mutual inductance with the weave angle of the braid are examined.

Shielding Effectiveness of Braided-Wire Shields

The use of shield topology concepts to design interference control is described. Starting with the postulate that electromagnetic environments can he separated by closed shield surfaces, the proper design of essential compromises such as insulated power and signal conductors, and openings for access and ventilation are deduced. The role of grounding is described and the relation of grounding conductors to shield surfaces is deduced. Some guidelines are given for determining how effective the shield needs to be. It is concluded that the effectiveness of a shield is usually limited most by interference propagating on insulated conductors passing through the shield, followed by leakage through apertures and diffusion through the shield walls.

Electromagnetic-Interference Control

Recent research in electromagnetic coupling between the interior and exterior of coaxial cables is described. Both tubular shields and shields with apertures are discussed with reference to the physical coupling mechanisms and their mathematical representations in terms of transmission-line models.

EMP Coupling Through Cable Shields

EMP coupling through cable shields

A transmission line model of coupling to power lines has been developed that shows the effect of ground conductivity, angle of arrival, polarization, and power line geometry on the open-circuit voltage at the end of the line. With this information, and the characteristic impedance of the line, the current and voltage to any termination may be calculated. This theory has been checked with experimental measurements and shows quite good agreement with measured values of current. The measurements were performed on scale models of power lines. The soil conductivity was scaled appropriately. The results show that, although the transmission-line model is not strictly applicable at the highest frequencies of interest, the error introduced by this approximation is less than the experimental error (? ± 10 percent). Measurements have also been made of the propagation of pulses down lines showing effects of attenuation, dispersion, junctions, bends, and spurs. Where available, theoretical calculations have been compared to measured results. From these measurements it is concluded that transmission-line models can adequately be used to predict propagation effects.

Edward F. Vance

Papers

Shielding Effectiveness of Braided-Wire Shields

Electromagnetic-Interference Control

EMP Coupling Through Cable Shields

EMP coupling through cable shields

EMP Coupling to Power Lines