Flow-induced charge accumulation in thin insulating tubes

The flow of semi-insulating liquids through insulating tubes can induce the accumulation of surface charge at the liquid-tube interface and generate electric fields intense enough to jeopardize the insulation. The space-time evolution of charge and fields is studied theoretically and experimentally for conditions typical of liquid-cooled power distribution equipment. With the experiment arranged so that charge generation is dominantly upstream of the insulating section, it is found that the absolute prediction of the space-time evolution of the electric field in the region surrounding the tube (and the field in the wall of the tube where damage is done) correlates with field transients measured at two locations outside the tube.