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.

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

Experimental comparisons of radio influence (RI) fields from long and short lines were made on a section of a 70-mile 345-kv transmission line. The results of these tests show that for line RI generation the long line RI level can be obtained from short test line data. Tests with a single RI source on the line are also described.

Experimental Comparisons of Radio lnrluence Fields From Short and Long Transmission Lines

Theoretically, the R-C decoupler network has been shown to provide both better attenuation and impedance-matching characteristics. Reactive elements alone (L-C) may give sufficient attenuation, but their low-loss characteristic is likely to alter the RI performance of the source side, returning part of the energy of some impinging pulses while passing others so that pulse fronts, tails, and amplitudes are transformed. Two sets of field tests were made to determine whether several sections of transmission line could be satisfactorily decoupled or isolated to RI, using the R-C decoupler network with the resistance shunted, for 60-cps purposes, by a relatively high inductance. Although questions regarding correct line termination and line attenuation at higher frequencies have not been answered, use of properly designed RI "filters" or decouplers has been shown to provide a high degree of RI isolation between sections of line. The tests were intentionally made on a single-phase line with no ground wire. Extensive field investigations would involve 3-phase conductors, plus one or two ground wires. All these conductors must be decoupled to get proper results during simultaneous testing of different line sections. From previous tests at Tidd, it has been found that heating the conductors-so as to produce in them a few degrees of temperature rise above ambient-greatly alters the RI and corona loss obtained during fog, drizzle, and damp weather in general. Current for heating cannot be drawn through the resistors of R-C decouplers.

Decoupling of Transmission Lines to Radio-Influence Voltages

This supplement to the "Bibliography on Extra-High-Voltage Systems, published in February 1959, includes 1,011 additional references from 1915 through 1960. The numerous frences published since 1958 indicate continuing high-level activity in this field in many countries.

R. S. Gens

Papers

Radio Interference Attenuation on Energized High-Voltage Transmission Lines: Measurement and Application