Measurement of Space Charge Distribution in a Corona Cage under Influence of different Atmospheric Conditions

Ion flow fields, partial discharge and space charge around transmission lines are phenomena that can cause power losses and can be responsible for flashovers on transmission lines, leading to losses or interruptions of the power supply. The influence of the varying atmospheric conditions is still not fully understood under DC excitation, especially when the applied voltage approaches the critical breakdown value. The typical environmental conditions (temperature, humidity and air flow or pressure) have a great influence on corona discharge. In this study, the impact of air flow on corona discharge, which is considered as one of the sources of space charge under DC conditions, was investigated. The experiments were done under controlled conditions in a laboratory-size corona cage with an aluminum Tern conductor at its center. The maximum DC voltage applied was ±150 kV. The purpose of this study was to investigate the mechanisms behind the accumulation of space charge on the aluminum HVDC conductor under different atmospheric conditions and have a better understanding of the major factors that influence the space charge processes under different atmospheric conditions. During the experiments, a corona camera (CoroCam8) was used to visualize the corona discharges along the conductor as well as the behaviour of space charges around the conductor. This has enabled to classify which of the three conditions have a greater impact. The corona is denser when the temperature is high for the positive voltage and for the negative voltage and the wet condition has more discharge. The mechanisms that can lead to flashovers during space charge accumulation were also presented.