Dielectric barriers play a great role in improving
the electric field homogeneity and improving dielectric behavior
of rod-plane gaps. SF6 gas is an expensive gas and has strong
greenhouse effect. So, it is a must to limit using it and develop gas
melanges having good insulating characteristics, with less cost
and no greenhouse effect. This work sheds light on determination
the optimum diameter, thickness, position and material of the
barrier in rod-plane gap. Influence of barrier presence on
electric field intensity and breakdown voltage of rod-plane gap is
studied. Influence of cone particle length and radius on electric
field and breakdown voltage of gap are examined. Effect of
barrier size (thickness and diameter), position and material on
the breakdown voltage is calculated. The SF6–N2-Air gas
melanges are tested at different percentages in order to study
effects of gas pressure, SF6 gas concentration in the mixture and
attain the optimal gas mixture with better favorable dielectric
strength. Finally, a comparison between breakdown voltages of
clean gap, clean gap with barrier, gap with wire particle and gap
with cone particle is presented to confirm importance of the
barrier in the gap and determining the most fatal case.