Electrical long-term stability and aging of polymeric composite dielectrics for cryogenic applications

• Applicant: Dr.-Ing. Ralf Puffer, since 8/2016
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2012 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 210575255

Within the first research project it is shown that regarding its low thermal contraction, its mechanical stability and its high short-term dielectric strength, syntactic foam is a proper electrical insulation for superconducting applications. The processes of breakdown under short-term AC, DC and impulse stress are described. But for applying syntactic foam in superconducting components of the electrical distribution network an error-free operation of syntactic foam under cryogenic conditions and over the duration of > 30 years must be ensured. Therefore, the long-term stability of syntactic foam at liquid nitrogen temperature (LNT) needs to be observed. At room temperature it is well known that electrical trees can grow up which leads to erosions within the foam and finally reduces the lifetime of the insulation system. The effect of electrical long-term stress on syntactic foam at LNT and if electrical trees can occur and grow up under cryogenic conditions in general is not yet investigated. Within the investigations of the second research project the long-term performance of syntactic foam will be observed. The main aspect will be the determination of the breakdown process within syntactic foam under long-term AC and DC stress and the definition of the influencing parameters. For this purpose lifetime characteristic curves of various syntactic foams will be ascertained. Furthermore, the deterioration effect of syntactic foam due to partial discharges will be determined at LNT. Due to the fact that superconductors operating at DC voltage do not show any electrical losses, DC applications show a high potential in the superconducting technology. Under DC stress the formation of space charges and space charge regions is expected. This regions cause field displacement which can influence the lifetime of syntactic foam. To identify how space charges can accumulate within syntactic foam at LNT and how these space charges influence the lifetime of syntactic foam will also be part of the second research project.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Armin Schnettler, until 7/2016