Evaluation of influencing factors on the electrical breakdown of syntactic foams at ambient- and liquid nitrogen temperature

Abstract:
Syntactic foam has shown a high potential for the possible application as solid insulating material for high-temperature superconducting equipment. Yet, only short-time investigations have been carried out, taking into account only the results at breakdown. In this paper, partial discharge phenomena are used as criterion for first damages. Different material combinations are investigated to rule out their influence on detoriation at ambient- and liquid nitrogen temperature before breakdown occurs. Further, samples which have been immersed in liquid nitrogen are optically investigated using a laser-scanning microscope and compared with reference samples to identify material changes due to the cooling process. During production or packaging of microspheres, it is possible that some microspheres crack. Therefore, the influence of broken spheres is investigated using 3D-FEM simulations. The simulations are run at conditions similar to the investigations to identify highly stressed areas.