Partial Discharge Inception Characteristics of LN2/Polypropylene Laminated Paper Composite Insulation System for High Temperature Superconducting Cables.

Partial discharge (PD) inception characteristics of liquid nitrogen (LN2 )/polypropylene (PP) laminated paper composite insulation system for high temperature superconducting (HTS) cables were investigated in terms of the volume effect and the V-t characteristics. The electrical and optical measurements of PD inception characteristics showed that initial PD could be generated between PP laminated paper layers, as well as in a butt gap. Using a parameter called statistically stressed liquid volume (S SLY) based on the discharge probability in both butt gaps and LN2 filled thin layers between PP laminated papers, we could systematically analyze and evaluate the volume effect on PD inception stress (PDIE). Furthermore, experimental results revealed that n values of V-t characteristics at PD inception were as high as 80-110. On the other hand, the lower n values obtained at breakdown were interpreted by the intensified PD development in thermal bubbles generated after the PD inception. [ABSTRACT FROM AUTHOR]