This paper presents theoretical investigation of
conducting particle-initiated breakdown in gas-insulated coaxial
configuration under high direct voltage. The presence of
contaminating conducting particles could seriously deteriorate
the dielectric strength of high voltage gas-insulated substations
(GIS) and gas-insulated transmission lines (GITL). This
deterioration depends on the shape of the particle, the type and
the pressure of the gas insulation, and the electric field. The
calculated breakdown voltage initiated by particle is obtained
by streamer breakdown criterion. The breakdown voltage
calculation calls first for an accurate calculation of the electric
field on and around the particle surface. The investigated gap
is a three-dimensional field problem due to the asymmetrical
space arrangement of the particle inside the gap. The particles
studied are of many different shapes and sizes such as spheres,
filamentary (wire) particles and fine spheres simulating the
surface roughness. To solve this problem, charge simulation
technique is used. The calculated field values are utilized in
evaluating the breakdown voltage. The effects of varying the
field nonuniformity, particle shape and size, gas type and
pressure on the breakdown voltage are investigated. The
calculated breakdown voltage values agree satisfactorily with
those measured experimentally and with those obtained
theoretically before. |
