Long AC power cables are increasingly used in both land and sub-sea power installations. Accurate estimation of the electrical behaviour of such cables is required to optimize the dimensioning of the entire power supply system. Cables designed with twisted wire screens and/or magnetic steel armours involve particular challenges. The PhD project will involve three dimensional finite element calculations, analytical formulations, and laboratory measurements and verifications. The aim will be to develop tools for choosing the appropriate cable design for various cable lengths and applications.