Discharging Microcavities and Electric Field Enhancement inside Cavities in HVDC XLPE Cables

This paper presents simulation and calculation results of electric field enhancement due to various cavity shapes in polymeric high voltage direct current (HVDC) cables. Two aspects are considered: field enhancement factor under DC and partial discharges (PD) in microcavities. PD can occur within defects already existing inside crosslinked polyethylene (XLPE) matrix under various conditions. These conditions are well known under alternative current (AC) but not so well under DC and DC with harmonics. Charges accumulation at XLPE/void interfaces are responsible for local field enhancement and discharges. Aim of this investigation is to identify if these effects, once combined, can increase microvoids size.