Electrode protrusions and particle chaining as factors affectingthe dielectric strength of air

摘要

Electrode protrusions and free particles have been demonstrated toreduce dramatically the breakdown voltage of insulating fluids. Thispaper examines two factors which affect the dielectric strength ofgaseous insulators: (i) shape and size of electrode protrusions; and(ii) particle chain formation. A computer program, based on the boundaryelement method, was employed for the computation of the electric fieldmodified by an electrode protrusion and/or a particle chain. The resultsregarding field enhancement were used as input data of another programthat evaluated the dielectric strength of the air-gap. Two types ofprotrusions were studied: hemispheres and hemispherically-ended rods.One to ten conductive spheres were considered to be attracted to suchprotrusions and chain at the top of them. The computations showed thatthe large protrusions are more harmful than the small ones and that thedielectric strength of the air-gap decreases with the number ofparticles in a chain