Corona-Generated Space Charge Environment in the Vicinity of HVDC Transmission Lines

Corona discharges occurring on HVDC transmission lines generate ionic space charges which fill the entire interelectrode space between the high-voltage conductors and the ground plane. In the case of unipolar lines, the polarity of the space charge will be the same as that of the conductor, while in the case of bipolar lines, space charges of both polarities mix in the region between the two conductors. The space charges drifting between the conductors and ground may produce electric induction effects on objects and people located under the lines. With the prospect of increased use of HVDC lines for purposes of long-distance bulk-power transmission, both theoretical and experimental studies are presently under way in order to clarify any possible effects and thus help in the proper design of the transmission lines. The physical mechanisms involved in the generation of the space charge environment as well as the production of any possible induction effects will be discussed. The State of the ARt of the theoretical analysis of dc ionized fields will be described. Finally, the problems of instrumentation and measurement techniques will be discussed and the practical measurement experience accumulated to date will be reviewed.