The influence of surface roughness and coating on the impulse breakdown voltage in SF/sub 6/

Breakdown at Multiple Protrusions in SF6 and CO2

“…Single-protrusion models have shown reasonable agreement with measurements when taking into account the availability of a start electron for an avalanche, streamer inception and leader propagation [34][35][36][37][38]. Surface roughness and the effect of insulating coatings in SF 6 have been investigated experimentally by [23,24]. CO 2 -based insulation is still less investigated than SF 6 , and investigations with fluorinated additives to CO 2 just recently appeared.…”

“…This is determined by the zero crossing of the effective ionization coefficient, which is specific for a gas. The slope of the effective ionization coefficient determines the sensitivity of the insulation system to the surface imperfections [13][14][15][16][17][18][19][20][21][22][23][24]. Thus, depending on the properties of the gases, the insulation performance is determined not only by the critical field of the gas but also by imperfections like surface roughness or particulate contamination.…”

Fabrication of Insulation Coatings on Additively Manufactured CuCrZr Electrical Windings

“…6c. Among the three samples, an inverse relation between the surface roughness and the BV was observed on the application of positive (non-pulsed) DC voltage [33].…”

“…It is defined as the threshold voltage at which the insulation starts to degrade and lose its insulating capacity [32]. BV being a function of coating thickness, studies have proven that for a positive voltage, an increase in the surface roughness leads to the decrease in the breakdown voltage of the coating [33]. For the current and upcoming generation of electric motors, a breakdown voltage of 1.5 kV and higher is favourable.…”