Methods to increase electrical breakdown threshold of polystyrene insulators

This paper discusses experimental studies conducted to determine the effects of methods used to increase the electrical stress limit of polystyrene dielectric samples. Surfaces of samples were laser annealed to create a more uniform surface and decrease voids where charge may accumulate. Geometry of the dielectric samples were considered with the aim of reducing electric field intensity at the triple point formed by the cathode, dielectric, and ambient environment, which in the presence of a strong electric field can become a source for electron emission. The dielectric samples were subjected to high voltage stress via a custom built partial discharge analyzer (PDA) capable of delivering 40 kVac, 20 kVdc or ac superimposed on dc. Preliminary results have shown that annealing of the surface has increased the hold-off voltage of the dielectric samples in comparison to benchmark samples that were not annealed. Studies have shown that reduction of the electric field intensity at the triple point can increase the voltage at which secondary electron emission avalanche initiates, which is widely agreed upon as the process preceding the onset of surface flashover. Experimental results are discussed and related to factors of interest including electric field intensity at the triple point, flashover hold off voltage and correlation with methods applied.