Currents Induced on Uninsulated Wires with Finite Conductivity
Abstract
Calculations of the source region EMP response of very long buried and elevated cables have generally been performed using transmission-line theory. That theory is useful when the response is dominated by an approximately TEM mode. Although an uninsulated wire supports such a mode, it is very difficult to excite. Other waves may dominate the response, invalidating the application of transmission-line theory. This study analyzes the response of an infinitely long, uninsulated wire with finite conductivity in a homogeneous material to a monochromatic voltage-generating source localized near the wire. Using Fourier techniques, an exact integral representation of the current induced on the wire is obtained by solving the full electromagnetic scattering problem. The integral is then expressed using contour integration as the sum of pole residues and an integral around a branch cut. The residues represent the contributions of TM modes of the wire. All of these modes damp out immediately except one, known as the principal mode. The principal mode is approximately TEM and hence can be treated by transmission-line theory. The branch-cut integral represents the contribution of an electromagnetic wave (known as a space wave) that radiates out into space. The space-wave cannot be treated by standard transmission-line theory. Numerical comparison of the magnitudes of the space- wave and the principal-mode contributions to the current for representative frequencies and wire resistances shows that the wire response is totally dominated by the space wave.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1983
- Accession Number
- ADA152191
Entities
People
- George Sherman