Effect Of Air Pressure On DC Corona Performance Of Conductor In Corona Cage

The first ultra-high voltage(UHV) direct current(DC) transmission line of±800kV is currently under construction.In the designing of UHV DC transmission line, the corona effect is one of the key issues to be considered.And the effect of altitude on the DC conductor corona is the basis of the design.In the thesis,a small corona cage together with fine wire conductors were used as the test model in the artificial climate room.Methods of corona current measurement,radio interference measurement and audible noise measurement were employed.The effect of air pressure on the characteristic of DC conductor corona was analyzed.And the results showed that the corona inception voltage is decreasing with the reduction of the air pressure.While under the same applied voltage,conductors with the positive polarity showed a louder audible noise of corona discharge,an increase of the corona current and a larger value of radio interference with the decrease of the air pressure whilst conductors with the negative polarity showed a louder audible noise of corona discharge,an increase in the corona current and a relative constant value of radio interference In order to find out the variation of corona characteristic of large size conductors under the change of air pressure,a large corona cage together with steel-cored aluminum strand wire,model 630/45,were used as the test model.Experiments in two test bases of low and high altitude were performed separately.Experiment results showed that conductors with either positive or negative polarity shows a louder audible noise of corona discharge,a larger value of radio interference and an increase of the corona current with the decrease of the air pressure while under the same applied voltage.