Comparative studies of DC corona losses in a corona cage and a point-plane gap

The effects of various parameters on conductor corona losses, under DC voltages, have been demonstrated through measurements in an indoor corona cage. Measurements were done in a point-plane gap to determine the characteristics of the positive and negative corona pulses. Test line measurements were also carried out to determine whether the corona losses are more dependent on conductor surface gradient or gap size. For a given gradient, the losses are higher for larger conductors under both polarities for solid and stranded conductors. Studies in the point-plane gap show that negative corona pulses are more frequent and smaller in magnitude, compared to the positive ones. In both the cage and point-plane gap measurements, the negative polarity corona current was higher. Test line results showed that for the same conductor surface gradient, the corona losses were higher for smaller gaps.