SF6 gas insulated switchgear plays an important
role in electric power networks all over the world due to its merits
as compared to traditional air insulated switchgear. According to
a numerous studies, it appears very difficult that any pure gas can
bring a solution to the issue of desirable insulation ability and low
environmental impact, so the mixtures composed of a strongly
electronegative gases with high dielectric strength such as SF6 and
ordinary gas (N2, CO2, or Air) are used to reduce the gas price
and liquefaction temperature. From this point of view, various
types of gas mixtures are used inside gas insulated switchgear
(GIS) and gas insulated lines (GIL) to give a higher dielectric
strength with lower cost and lower environmental impact. In this
paper, the Finite Elements Method (FEM) is used to evaluate the
potential and electric field distributions on and around multi
contaminating particles. Two cases are studied in this work, the
first is that there are three contaminating particles rested at
ground plate, and the second case is that there are two particles,
one of them is rested on the ground plate and other is hovering
inside the gap between two parallel plates. The effect of spacing
between the particles on the electric field values is studied. The
breakdown voltage calculations under uniform field in case of
clean gap and non-uniform field in case of gap with multiparticles
contamination are studied. The effect of gas pressure,
SF6 gas concentration in mixture and the spacing between
particles on the breakdown voltage calculations are also studied. |
