Electrical breakdown in an electric discharge showing the ribbon-like plasma filaments from a Tesla coil. Electrical breakdown or dielectric breakdown is a rapid reduction in the resistance of an electrical insulator when the voltage applied across it exceeds the breakdown voltage.This results in a portion of the insulator becoming electrically conductive.ue to hydrodynamics breakdown in liquids seems to be more complicated: using two spheres in the gap between the electrodes additional pressure is exerted by the non-linear field strength. Electrical breakdown occurs within a gas (or mixture of gases, such as air) when the dielectric strength of the gas is exceeded.