Simulation of DC Electric Fields on the Layer Structure of PPLP for Butt-Gap Conditions in HVDC MI-PPLP Cable

The electric and thermal properties of HVDC MI-PPLP cable have recently been improved such as dielectric performance and maximum allowable temperature. However, its de electric field characteristics have not been fully investigated. As a lapped cable, its main insulating material is PPLP, which has a special composition of Kraft-PP film-Kraft. This prevents conventional de electric field analysis for the bulk type model from being directly applied to HVDC MI-PPLP cable. Therefore, the layer structure should be considered for HVDC MI-PPLP cable. In this paper, we focused on the difference in the de electric field properties between the bulk and layer type model, which were determined at a steady state and polarity reversal. In order to determine the difference in the number of the butt-gap, single and double butt-gaps were simulated and compared in terms of the butt-gap conditions. Particularly for the double butt-gap, it was possible to investigate the effects of size, position, and formations using de electric field simulation. Based on the de electric field analysis, meaningful information about the butt-gap characteristics of HVDC MI-PPLP cables was obtained.