Smooth Conductor Research Articles

Stimulated Raman scattering by an intense relativistic electron beam in a long rippled magnetic field

For the first time, the parametric coupling of the negative-energy cyclotron and space-charge modes to a fast coaxial waveguide structure is observed. The coaxial waveguide smooth center conductor is internally loaded to maintain a 5% ripple of 1.4-, 1.6-, or 2.0-cm periods on the background axial magnetic field throughout the interaction region of 70 cm. The parametric coupling may be considered a stimulated scattering process with the rippled magnetic field of zero frequency in the lab frame appearing as an electromagnetic pump wave in the beam frame, with 30-MW/${\mathrm{cm}}^{2}$ power density imparting to the electrons a quiver velocity ${V}_{\mathrm{os}}\ensuremath{\simeq}0.1c$. As predicted by theory, the frequency of the microwave radiation generated by the negative-energy cyclotron mode decreases with increasing magnetic field while remaining constant for the negative-energy space-charge mode. Power levels from 1 to 5 MW have been measured at mm and cm wavelengths. Radiation at frequencies of $\frac{2{\ensuremath{\gamma}}^{2}V}{L}$, where $V$ and $L$ are the beam velocity and ripple period, respectively, has been observed at high magnetic fields with an exponential-growth rate consistent with parametric coupling theory. This mechanism could be employed as a tunable generator of millimeter and submillimeter wavelength radiation.

A new thermal rating approach: The real time thermal rating system for strategic overhead conductor transmission lines -- Part I: General description and justification of the real time thermal rating system

For the first time a Real Time Thermal Rating System has been developed for overhead transmission lines using actual meteorological data and real-time conductor temperatures and line loadings. This System provides, on a probability basis, much higher ampacity ratings than those derived from conventional methods. As a portion of this System, a steady state thermal rating procedure is presented in the companion paper, which includes forced convection heat transfer equations taking into account the effect of wind turbulence or gustiness, conductor yaw (wind direction), conductor height above ground, smooth versus rough (stranded) conductor surfaces, the proximity of conductors in a bundle, and conductor pitch. A natural convective heat equation is developed for stranded conductors. The conductor temperature is solved directly without resorting to an iterative solution.

Application of complex ray tracing to scattering problems

Representations and geometric constructions associated with complex points, complex lines, and complex rays are introduced. They are applied to the problem of scattering of an evanescent plane wave by a conducting circular cylinder. This problem has an exact solution, which provides a check of the validity of complex ray tracing and suggests more general applications. An important role is played by the transformation that maps the point of reflection, on the complex extension of the scattering surface, onto the trace in real space of the complex reflected ray. For the particular problem considered, the phase and amplitude of the reflected field are computed and the "phase paths" and "phase fronts" are constructed. The reflected field and phase paths obtained in this manner are not to be taken in their entirety because some reflection points are not "illuminated" by the incident wave, and because the reflector may be only part of the cylinder. Tentative selection and truncation rules are used which yield good agreement with the exact solution over some regions. The disagreement, where it occurs, comes-as it does for real rays-from neglecting the diffracted field such as the creeping waves around smooth surfaces and, in the case of truncation, the edge waves from the discontinuity. Some consideration is given to scattering by an arbitrary smooth conductor. Some problems peculiar to the use of complex rays are stated.

Calculation of Maximum Voltage Gradients, Part I: Bundle Conductors

A new analytical method is described for computing the maximum field intensity at the surface of any smooth conductor of a multiconductor system forming a regular polygon. In this method, each conductor in the system is replaced by a line charge at its center equal to the charge on its surface plus a system of line dipoles to account for the proximity effect. The line dipoles in the conductor under consideration are treated as individual line charges. The degree of accuracy of the method, for the two-conductor case, is checked against the known exact solution. It is shown that this method is very accurate even for small conductor spacing to diameter ratios (less than 6), where existing analytical methods become very inaccurate.

Analysis of irregularity factor of stranded conductors

The paper presents a theoretical derivation of the irregularity factor of stranded conductors, the irregularity factor being defined as the ratio of maximum surface voltage gradient of a stranded conductor to that of a smooth conductor of the same overall diameter and of the same charge. The method is based on conformal mapping of circular-arc triangles. When applied to 7-, 19- and 37-strand conductors, the irregularity factors obtained were 1.407, 1.436 and 1.445, respectively. The field around the conductor is also completely known from the analysis.

Corona Phenomena from Water Drops on Smooth Conductors under High Direct Voltage

The effect of high direct voltage on the formation and dislodging of water drops hanging from a smooth conductor will be shown and used to explain the resulting corona characteristics, such as pulse amplitude and repetition rate, audible noise, radio influence (RI) and loss current, and corona current waveforms. Phenomena taking place during the conductordrying period are also explained. The relationship between the number and spacing of points on a smooth conductor, on one hand, and RI and loss current, on the other, is demonstrated. Results obtained from water-drop experiments are compared with those from experiments using metal points of various shapes.

High-Voltage Corona in Air

In the last few years contributions to corona literature by Holm, Ryan, Willis, and others have shown that the space charge liberated by alternating corona reacts on the corona to a high degree in determining its characteristics. This investigation studies the nature of these effects as influenced by variation in the limits of travel of the space charge. The three properties of corona readily lending themselves to experimental observation, the wave form and the value of the corona current, and the corona loss, have been observed when high alternating voltages are applied to a small smooth cylindrical conductor placed successively along the axes of four sizes of metal cylinders. In addition four frequencies of the alternating voltages were used. All the work has been done under atmospheric conditions. The theory of the influence of space charge as developed by Holm has been tested by experiment and a marked discrepancy is indicated. Values of power loss due to corona, as measured, differ appreciably from those predicted by Holm, but in general follow the quadratic relation suggested by Peek. Unusually large and clear oscillograms afford much interesting qualitative information as to the influence of space charge travel on corona.

Abridgment of high-voltage corona in air

In the last few years contributions to corona literature by Holm, Ryan, Willis, and others have shown that the space charge liberated by alternating corona reacts on the corona to a high degree in determining its characteristics. This investigation studies the nature of these effects as influenced by variation in the limits of travel of the space charge. The three properties of corona readily lending themselves to experimental observation — the wave form and the value of the corona current, and the corona loss — have been noted when high alternating voltages are applied to a small smooth cylindrical conductor placed successively along the axes of four sizes of metal cylinders. In addition, four frequencies of the alternating voltages were used. All the work has been done under atmospheric conditions. The theory of the influence of space charge as developed by Holm has been tested by experiment and a marked discrepancy is indicated. Values of power loss due to corona, as measured, differ appreciably from those predicted by Holm, but in general follow the quadratic relation suggested by Peek. Unusually large and clear oscillograms afford much interesting qualitative information as to the influence of space charge travel on corona.