This project aims to investigate the impact of inherent defects, space charge dynamics, partial discharges, electrical trees and power quality on the electrical performance of lapped cable insulation under high DC stress. Mass impregnated insulation constructed from lapped PolyPropylene Laminated Paper (PPLP) tapes is of current topical interest in this field. Fundamental understanding of the performance of this insulation and development of novel operating methodologies are urgently required in order to meet the challenges faced in HVDC connection of offshore wind farms and in the creation of HVDC super-grids.