DC Breakdown and Surface Potential Behavior of Epoxy/Al2O3 Nanocomposites at Cryogenic Temperature

• Published in: IEEE transactions on applied superconductivity Vol. 30; no. 8; pp. 1 - 7
• Main Authors: Jiang, Tie, Chen, Xiangrong, Dai, Chao, Guan, Honglu, Paramane, Ashish
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aluminum oxide; Cables; Carrier mobility; Cryogenic engineering; Cryogenic temperature; Cryogenics; Current carriers; dc breakdown; Dielectric breakdown; Dielectric properties; Dielectric strength; Electric breakdown; EPOXY nanocomposites; Epoxy resins; High temperature; Liquid nitrogen; Nanocomposites; Nanoparticles; Space charge; surface potential decay (SPD); Temperature; trap characteristics
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2020.3007624

For high temperature superconducting (HTS) dc cables, one key issue is the necessity of using polymer dielectrics with higher dielectric strength at cryogenic temperature in liquid nitrogen. Nanocomposites have played an important role in improving the dielectric properties of epoxy resin (EP). This article investigates on the dc breakdown strength and the surface potential behavior of the epoxy/Al 2 O 3 nanocomposites (0, 1, 3, 5 wt%) at the room and cryogenic temperatures. Moreover, the trap distributions are analyzed from the surface potential decay (SPD) measurement. The possible effect of the trap distributions on the dc breakdown strength is discussed with the valid results. The measurements show that the dc breakdown strength and the initial surface potential continually increased with the nanoparticle addition up to 3 wt% at both room and cryogenic temperatures, and decreased thereafter. The enhancement of the breakdown strength and the initial potential is also found at cryogenic temperature. Besides, the addition of the nanoparticles decreased the rate of SPD compared with the pure epoxy. It is proposed that the higher trap density and trap level enhances the dc breakdown strength. Interestingly, under the cryogenic environment, the nanoparticles addition significantly affects the trap distributions, which further influences the dielectric strength. The enhanced dc breakdown strength is attributed to the reduced space charge formation, the charge carrier mobility and the energy of the charge carriers within the sample bulk.