KEPCO 765 kV transmission system development: corona and electric field effects studies

This paper describes corona and electric field effects studies of a 765 kV double circuit test line. In Korea there are many mountains and it is very difficult to get the right of way because the population density is very high and the territory is small. So Korea Electric Power Corporation (KEPCO) decided to build one double-circuit 765 kV line of vertical arrangement configuration instead of two single-circuit 765 kV lines of horizontal configuration. Corona performance on several candidate conductor bundles has been investigated with a corona cage since 1984 by KEPRI. We have known that a bundle of 6-Rail (29.61 mm) conductors per phase is the optimum and its audible noise (AN) level L ₆₀ in the corona cage was measured as 45.0 dB(A) in GE method. To investigate the electrical environmental impact of the future commercial line with this conductor bundle, KEPRI built a full scale 765 kV test line in 1993 as the second step study. Long-term measurements have been made in this double-circuit test line. We have found that the AN data were very close to that predicted by BPA Corona and Field Effects computer program, however, the RI data in fair weather was higher than the predicted by the BPA program by 2.4 dB (μV/m). AN L ₆₀ in foul weather is below 50 dB(A). We think the 6-Rail conductor bundle is the optimum size in the 765 kV double-circuit transmission line from the environmental view-point