Theoretical investigation of the onset voltage of negative corona on stranded
conductors is described in this paper. The method of calculation is based on
the criterion developed for the formation of repetitive negative corona
Trichel pulses. This calls first for an accurate calculation of the electric field
in the vicinity of stranded conductors. The investigated gap is a
three-dimensional field problem. To solve this problem, a new modification
of the charge simulation technique is presented, where the simulation
charges are helical of infinite length. Laboratory measurements of the onset
voltage on stranded conductors are carried out to check the accuracy of the
present calculations. The effects of varying the field nonuniformity on the
onset voltage values are investigated. The calculated onset voltage values for
stranded conductors agree satisfactorily with those measured experimentally