On Electrical Aging of Oil-Impregnated High-Voltage Dielectrics

Experiments have been carried out to determine the partial discharge performance of laminated Kraft paper/oil dielectric (1.3 mm thick). As with conventional corona pulse detection equipment, the pulses were measured on a radio interference (RI) meter which proved well suited for this purpose. The type of insulation investigated has high long-term electric strength if correctly assembled, even when small voids are present in the dielectric. If discharges do occur, a certain recovery interval is required to regain almost full electrical strength, because of the time needed to absorb gases formed by the discharge. The data obtained on the test specimens were confirmed by long-term tests carried out on oil-filled instrument transformers.