Degree of corona saturation for HVDC transmission lines

The DC electric field and ion density are two of the electrical quantities of interest that characterize the electrical environment of HVDC (high-voltage direct-current) transmission lines. The author presents an overview of the electric field and ion environment of HVDC transmission lines and introduces the concept of degree of corona saturation. It is shown that the use of the degree of corona saturation along with the electrostatic (corona-free) and corona-saturated conditions as lower and upper limits allows the DC electric field and ion density can be simply and quickly calculated for a variety of weather conditions and line configurations. The proposed method is simple and straightforward, is fast and easy to use, and allows the electric fields and small air ion densities to be calculated for complex line designs and right-of-way cross sections