摘要:

Three aspects of the problem of electromagnetic interaction with transmission lines are reviewed. The various source terms appearing in the transmission line equations are discussed, including the coupling of common to differential mode. The interaction of an electromagnetic pulse with above-ground multi-conductor power lines is treated directly in the time domain by keeping an account of each scattering term. Finally, two simple phenomenological corona models are proposed, results derived from which are compared with recent experimental data.

ISSN:0272-6343    

DOI:10.1080/02726348808908211

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The analysis of the coupling of electromagnetic pulses with transmission lines is rigorously formulated in the spectral domain by means of a Fourier transform, on the line axis, of the currents and of the total electromagnetic field. By means of this formulation, the validity of the telegrapher model and its limitations are clearly assessed; and the spectral domain counterpart of the telegrapher model is presented along with the modifications required to deal with transmission lines over an unperfectly conducting ground. To demonstrate the usefulness of the spectral theory on a practical case that cannot be studied by the telegrapher model, the formal solutions of the problem of a single buried wire of arbitrary length are obtained, by means of the Wiener-Hopf technique. A discussion of the numerical methods that can be used to solve the general equations obtained by the spectral theory is also included.

ISSN:0272-6343    

DOI:10.1080/02726348808908212

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The early-time responses of overhead lines to an exponentially decaying electromagnetic transient are considered. The early-time current, voltage, and radial electric field induced in a wire is investigated. A. transient electromagnetic plane wave produces the driving electromagnetic force for the wire. The wire is assumed to be infinitely long and perfectly conducting. The wire is situated above a finitely conducting plane earth. The plane wave is assumed to have its magnetic field perpendicular to the axis of the wire. The time history of the plane wave is described by a 5O kV/m decaying exponential pulse. It Is found that peak currents of over 5 kA and associated voltage crests of several megavolts occur for small incident wave angles. These values are comparable to small lightning strikes to power transmission line structures. The rates-of-rise of the induced currents are greater than 100 kA per microsecond which exceeds the maximum rate-of-rise of nearly all lightning negative first strokes.

ISSN:0272-6343    

DOI:10.1080/02726348808908213

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The paper discusses basic principles and validity limits of the field–to–transmission line coupling calculation using Transmission Line (TL) theory. Particular attention is given to the EMP–power lines interaction. A detailed review of the fundamental equations and method of solution is given, considering that two equivalent formulations are possible. These result in two equivalent circuits for an elementary section of the transmission line, each characterized by different excitation source terms. The excitation sources for the case of a nuclear EMP excitation are modeled, and the solution of the equations is given taking into account the effect of a lossy earth serving as a return conductor. In order to assess the validity limits of the TL approximation, a comparison is made between results obtained by the authors using this approach, with those published in the literature using the scattering theory. The effect of shield overhead wires on the response of a power transmission line to an EMP is also investigated. It is shown that overhead shield wires, placed in the vicinity of the phase conductors for the purpose of providing protection of the system from lightning surges, can be considered effective also when the power line is illuminated by an incident electromagnetic pulse.

ISSN:0272-6343    

DOI:10.1080/02726348808908214

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726348808908215

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Consider a perfectly conducting uniform two-wire transmission line of finite length illuminated by a plane incident electromagnetic wave. The resulting voltage and current response is calculated by using the transmission line theory where the external excitation is modelled by distributed voltage and current sources. The line equations form a set of coupled linear nonhomogeneous ordinary differential equations which are transformed into a more convenient compact decoupled form. Analytical approaches to solve the compact line equations as well as the appropriate boundary conditions are presented. The compact formulation may be easily generalized to consider more complex systems than two-wire lines. In the frequency domain great importance is attached to the mathematical aspects (in the sense of analytic functions) of the line theory. The solutions are expanded in terms of residues and singularities by using a special application of Mittag-Leffler's theorem. Two inversion methods of the Laplace transform (IFT and SEM) to get the transient time domain results are discussed in detail. Examples of voltage and current responses resulting from numerical experiments are given in frequency domain and in time domain.

ISSN:0272-6343    

DOI:10.1080/02726348808908216

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A procedure based on trasmission-line theory, is presented for the evaluation of the effects produced by an EMP wave on a multiconductor power line. The high-altitude nuclear EMP is considered as an incident wave towards the ground; the total field is the sum of the incident wave and the wave reflected from the ground surface. The transmission system is represented in the frequency domain by an accurate simulation model, which takes account of earth and conductors skin effect. Non-linear phenomena, such as corona and flashover, are not considered. The EMP-line coupling results in per-unit length series-voltage and shunt-current sources. Analysis of the multiconductor circuit with distributed impressed sources is performed by using matrix operators in integral expressions, which are calculated numerically. The transient voltages and currents are obtained by a discrete inverse Fourier transform. The EMP effects induced on a distribution power line with different terminal conditions are computed.

ISSN:0272-6343    

DOI:10.1080/02726348808908217

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper deals with the study of transients in multiconductor lines excited by interfering plane wave disturbances. By means of the telegrapher's equation model, we derive a general expression for the Laplace transform of the end voltages and currents and show that it. depends on the line characteristics, on the geometry of the interfering wave, and on the terminal loads, which are assumed to contain linear non-reactive elements. Additional assumptions lead to expressions that can be analytically transformed in the time domain. These closed-form results, despite their apparent limited applicability, provide a useful insight into the electromagnetic mechanisms of the interferences and constitute a valid check for more complex all-numerical simulations. Finally, we present the results of a computer program that can handle lines with sufficiently general characteristics (e.g., losses, finite conductivity of the ground, and pulses of arbitrary shape).

ISSN:0272-6343    

DOI:10.1080/02726348808908218

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper presents an application of the transmission-line theory to determine the coupling of disturbing waves on coaxial or multiwire shielded cables. First the external problem is analyzed in the case of a line parallel to the ground and examples are given for an illumination either by the field radiated by a lightning stroke or due to a nuclear electromagnetic pulse. The influence of geometrical or electrical parameters such as the cable length, the angle of illumination and the ground conductivity are examined. Penetration of energy into the cable is studied for a coaxial cable. Then some experimental results on multi-wire shielded lines are presented in order to highlight the various mechanisms which can cause a differential voltage between each pair of the inner lines. Lastly, application of a simple numerical model shows the relative influence of dissymmetries either in the structure of the cable or in the load impedances connected at both ends.

ISSN:0272-6343    

DOI:10.1080/02726348808908219

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The rigorous study of scattering problems due to the coupling of electromagnetic waves with wire structures can be done directly in time domain by means of various methods, namely by using integral equations and finite difference solutions.

ISSN:0272-6343    

DOI:10.1080/02726348808908220

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor