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.The
mixtures composed of a strongly electronegative gases with high dielectric strength such as SF6
and two ordinary gases such as N2 and Air or CO2 and Air with a various fractional
concentrations are used in this paper 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)
to give a higher dielectric strength. In this paper, the Finite Elements Method (FEM) is used to
evaluate the potential and electric field distributions on and around contaminating filamentary
wire particle at two positions, first is resting on the earthed plate and second is hovering inside
the gap. The effects of particle dimensions such as (length, radius) and gap spacing on the
electric field values are also studied. The breakdown voltage calculations under uniform field
in case of clean gap and non-uniform field in case of gap with particle contamination are
studied. The effects of gas pressure, SF6 gas concentration in mixture, gap spacing and particle
dimensions on the breakdown voltage calculations are also studied. |
