Besides the option of HTS cables as retrofit elements in densely populated areas, the technically most attractive aspect of HTS is the possibility of high power transmission at reduced voltage. In this paper we concentrate on this second aspect. High power/low voltage HTS lines are analysed from the technical and economical point of view in two case studies: (i) a 110 kV/1 GVA transalpine line replacing a 380 kV overhead line and (ii) a 30 km/600 MVA line connecting a nuclear power plant with a densely populated area. The technical analysis shows that high power cables at reduced voltages (>20 kV) and with acceptable electrical properties (losses, dimensions, reactive power) are technically feasible. In the economical analysis, the life cycle costs of the different scenarios are calculated including the investment and operation costs of the cable, the undergrounding costs and the costs of secondary equipment (fault current limiter, converter, cooling). The analysis shows that the DC HTS line can be interesting, whereas the AC HTS cable systems can hardly compete economically with conventional AC cable installations.