Dielectric thermal-mechanical analysis and constrained high voltage DC cable rating

For most mass-impregnated (MI) paper insulated HVDC cables, the dielectric strength is found to be weakened when the cable cools, resulting from the creation of dielectric cavities. To better understand the cavity creation, two mechanisms are frequently compared, based on the imperfect impregnation process and sheath plastic deformation respectively. This paper presents an analytical calculation of cable internal pressure, which is applicable to both cavity creation mechanisms. It demonstrates that the two mechanisms can jointly place constraints on the MI cable rating, by limiting the overall rating-related thermal expansion.