Calculation of the electric field distribution under thepoint-plane gap configurations using the FEM

摘要

In our previous work on the prebreakdown density change steamersin cyclohexane, we found that the structures of streamers differ by thetip radius of needle electrode and the applied voltage. We hadconsidered that this might be caused by the difference of the fielddistribution between gap, and were eager to calculate it to makeconsiderations on the phenomena. In this paper, we employed the finiteelement method (FEM) to calculate the field under point-plane gaps. Thegap length and the plane diameter were set to 5 mm and 30 mmrespectively, and the field distributions for the needles with tip radiiranging from 0.1 μm to 30 μm were calculated. Although employingthe classical method, we had difficulties in the calculation caused bysevere non-uniformity of the field. By employing an optimization methodbased on the potential lines, a mesh, which is a combination ofapproximately 5,000 triangular elements of different sizes differingfrom 10-8 m to 10-2 m, was obtained and we couldcalculate the field satisfactorily well. Using this calculation method,the field distribution at the streamer, inception voltage in cyclohexaneobtained in our previous work was calculated and the mechanism of thesteamer initiation is considered