Theoretical calculation of corona losses for practical unipolar dc transmission line configurations presents considerable difficulty because of the nonlinear nature of the equations describing the space-charge fields. The application of numerical methods to obtain solutions of practical interest is discussed. One of the difficulties in the analysis of space-charge fields is the determination of the actual charge distribution around the conductor in the corona. A numerical iterative method of computing this charge distribution is presented. The method is applicable to any general configuration for which the space-charge-free field can be calculated. The line- to-plane configuration is considered. A method of including the effect of conductor surface irregularities in the theoretical calculation of corona losses is outlined, and it is suggested that, by the same method, Popkov's formula may also be modified to make it applicable to lines with practical transmission-line conductors. Calculations by the method of analysis developed as well as by the modified Popkov equation are compared with experimental results.

Analysis of Corona Losses on DC Transmission Lines: I - Unipolar Lines

The method of calculating corona losses, developed for unipolar operation mode, is used in the paper to study corona loss characteristics of several practical HVDC transmission lines. Detailed results on the influence of various line parameters upon corona loss characteristics of monopolar lines with single as well as bundle conductors, of homopolar lines, and of monopolar lines with overhead ground wires are given.

Corona Loss Characteristics of Practical HVDC Transmission Lines, Part I: Unipolar Lines

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

The effects of wind on corona discharges from HV dc transmission lines were studied using two laboratory models. One model was used for studying the corona vs. wind characteristics of discrete metal projections from smooth conductors, while the other dealt with corona on stranded conductors. The investigation encompassed both 2-conductor and conductor-to-plane configurations at wind speeds up to 50 miles per hour. It was found that both corona loss and radio-influence voltages (RIV) were sensitive to wind in the 2-conductor configuration but not in the conductor-to- plane configuration. The results are correlated with previous findings and with the theories of corona discharges.

A Laboratory Study of the Effects of Wind on DC Corona

Pulses and Radio-Influence Voltage of Direct-Voltage Corona

Corona loss and radio interference (RI) from one single Drake conductor and one Drake 2-conductor bundle, installed on two short test lines have been measured at direct voltages up to 600 kv, positive and negative, under a variety of weather conditions and voltage levels. The Drake conductor is a 1.108-inch-diameter 795-MCM (thousand circular mil) ACSR (aluminum cable steel-reinforced) conductor with 16 outer strands of aluminum each of 0.175-inch diameter. Comparisons of corona-loss performance of these two conductor systems, obtained from both short-term voltage increment tests and from long-term constant voltage tests, are given. Equipment for loss measurements, including a shielding method which substantially reduces the measurement errors ordinarily introduced by losses through solid line insulation, is described. Results obtained from occasional surveys of RI at frequencies up to 10 mc (megacycles) are presented.

B. Rakoshdas

Papers

Pulses and Radio-Influence Voltage of Direct-Voltage Corona

An Investigation of Corona Loss and Radio Interference from Transmission Line Conductors at High Direct Voltages