Computation of corona onset using the ring-charge method

A new method of computing the corona-onset voltage, in wire-plane systems, is described. It is based on the principle that the positive ions, formed during the growth of the avalanche, are concentrated in circular rings located at places where ionisation collisions are believed to occur, and the number of electrons at the avalanche head is doubled. Onset level is reached when the resultant electric field at the anode tip drops below a certain value. The method has been successfully applied to wire-plane configurations subjected to positive d.c. stress in atmospheric air. Results are in excellent agreement with those found in the literature.