Metallic particle contamination is one of the areas of insulation design that
are considered critical. This paper demonstrates the control of metallic
particles in gas insulated bus duct (GIBD) by using dielectric coating on the
inside surface of the outer enclosure of a coaxial electrode system. Several
models of GIBD with single and multi-contaminating particles will be
studied. In this paper, the Finite Elements Method (FEM) is used to evaluate
the electric field distribution on and around single and multi-contaminating
wire particles which in contact with dielectric coating of earthed enclosure
inside GIBD. The effect of changing the length and the radius of middle
particle for multi-contaminating particles on the electric field values are
studied. Breakdown Voltage calculations for gas mixtures with single and
multi-contaminating wire particles are studied. The effects of gas pressure on
the breakdown voltage for various fractional concentrations of SF6-gas
mixtures with and without particle contamination and also with and without
coating of earthed enclosure are studied. The optimum gas mixture which
gives higher dielectric strength with lower cost is also determined. The effect
of coating thickness of earthed enclosure on the breakdown voltage for
various fractional concentrations of SF6-gas mixtures is also studied. Finally,
the effect of length and hemi-spherical radius of multi-contaminating
particles on the breakdown voltage with various SF6-gas mixtures and
varying gas pressure one time and another time with fixed pressure are
studied.