It is well recognized that direct current and direct voltage offer special advantages for both land and sea cable systems, both with regard to power transmission capability, losses, as well as possible transmission length due to no capacitive currents. As cable systems were used very early in large cities, one of the first applications considered for HVDC was to use it for city infeed and some schemes were also built. However, it turned out that the cost for the stations was too high and that the savings on the cable part were not high enough to justify the high costs of the converter stations, even considering other possible benefits of the HVDC techniques such as fast control of active power and almost no contribution to fault currents. Therefore, in this paper investigation of the performance of bipolar and multi-Terminal HVDC systems under different operating conditions are conducted. Models representing some actual HVDC systems, and giving voltage profiles are produced under different working conditions, and are simulated using Matlab/Smiulink. Corresponding computed results are obtained.