Research on the Influence of Humidity on the Trichel Pulse Waveform of Coaxial Electrode Negative Corona

Environmental humidity is one of the important factors affecting corona discharge in transmission lines. Studies have shown that corona loss in transmission lines increases sharply when relative humidity rises. As an important development stage of negative corona discharge in transmission lines, studying the waveform changes under different humidity conditions plays a crucial role in controlling corona discharge in high-voltage direct current transmission lines. The influence of humidity on the corona discharge parameters was calculated using the Wielang approximation, a fluid dynamics model was established, and the negative polarity corona discharge characteristics of the coaxial electrode structure in the air gap under atmospheric pressure were studied, and the Trichel pulse waveforms at different relative humidity were obtained. The electric field intensity and the density distribution characteristics of three types of charged particles (positive ions, electrons and negative ions) in the discharge region at different stages were analyzed and discussed, and the mechanism of variation of the pulse waveform at different relative humidity was presented. Through simulation, it was found that as the relative humidity increased, both the average amplitude and frequency of the discharge pulses increased, and corresponding waveform characteristics appeared in the wire discharge at different relative humidity: when the relative humidity was in the range of 0% to 20%, the wire discharge all appeared in the form of typical Trichel pulses; When the relative humidity was in the range of 20% to 55%, the discharge pulses were accompanied by larger base currents; When the relative humidity is between 55% and 65%, the amplitudes of the discharge pulses alternate in a regular pattern of large and small; When the relative humidity is in the range of 65% to 80%, the descending phase of the larger amplitude pulse is accompanied by a continuous repetition of smaller amplitude pulses; When the relative humidity increases above 80%, the discharge waveform shows a steady current without pulses. The results of this study can provide a theoretical basis for the negative corona discharge waveforms of the air-gap coaxial electrode structure at different humidity levels and provide a reference for the microscopic physical mechanism of corona discharge in transmission lines.