Influence of Butt Gap on Partial Discharge Inception Characteristics in Liquid Nitrogen/PPLP Composite Insulation System

Abstract

It is important to elucidate partial discharge (PD) inception characteristics in LN₂/solid composite insulation system for the practical insulation design of high temperature superconducting power cables. Especially, butt gaps between laminated insulating papers for electrical insulation of superconducting power cables may induce PD and deteriorate the insulation performance under high voltage operation.
This paper discusses PD inception characteristics in LN₂/PPLP composite insulation system with a butt gap. We obtained PD inception electric field strength (PDIE) for different butt gap location and surface pressure on PPLP. V-t characteristics for PD inception were also described in this paper. Experimental results revealed that (1) PD with 2_??_30pC were detected at inception voltage in the butt gap between PPLP. (2) PD IE with a butt gap in the middle layer was higher than those in the top and bottom layers. (3) PDIE was independent of the surface pressure on PPLP. (4) n value of V-t characteristics for PD inception decreased down to 33.7 at the lower surface pressure on PPLP.