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.