Bubbles and breakdown of liquid dielectrics

According to the bubble model the cause of breakdown is the bubbles of micron sizes that exist at electrodes. Several reasons of stationary bubbles existence and emergency on electrodes are discussed. The appearance of "effective" electron in the bubble at short pulses is determined by polar admixtures at electrodes and lead to discharges in it. Emergence of surface and space charge near bubbles poles lead to bubbles deformation due to Coulomb forces. Bubble elongation causes field increase in liquid near bubble poles. Breakdown initiates in liquid phase when this field reaches critical value that depends on the liquid sample and the polarity of initiating electrode. The equation of bubble growth is computed. The basic factors that define electrical strength in model are external factors: the pressure, temperature; properties of liquid: dielectric permittivity, vapour pressure, viscosity, surface tension, density, pulse voltage parameters: the rate of pulse rise, pulse width; properties of liquid-electrode interface that determine charge injection. This performs to compute the well-known breakdown dependencies.