Onset voltage of negative corona in point-cup gaps

In this paper, the onset voltage of negative corona is theoretically predicted for point-cup gaps positioned in air. The method of calculation is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. Field distributions are determined through charge simulation method coupled with least-square error method for optimal charge distribution and accurate field computation. Different gap dimensions are studied. Accurate distributions, not only for the potential but also for the electric field have been obtained throughout the entire interelectrode space. Negative onset voltage of corona is calculated at different gap dimensions and different air pressures.. The values of calculated onset voltages agreed well with those measured experimentally within 5 \%.