Flashover voltage of PE300 insulators embedded in liquid nitrogen with and without gas bubbles

Liquid nitrogen is often used for cooling as well as high voltage insulation purposes in superconducting power applications. The high voltage design with respect to flashover voltage along the solid insulator to liquid nitrogen interface is an important issue for such devices. The use of PE300 as solid insulator material is possible in the case of moderate compressive loads. PE300 has remarkable benefits for cryogenic high voltage applications e.g., shock cool down resistance, high flashover resistance, and simple mechanical processing. High voltage tests with alternating, direct and standard lightning impulse waveforms were performed with PE300 disks embedded in liquid nitrogen at 0.1 MPa absolute. Nitrogen gas bubbles generated by a heater have impact on withstand voltages especially for impulse waveform. Tendency to flashover behavior instead of sparkover in edge region with enhanced field was found for an electrode setup with beveled edge.