ECONOMICS OF POWER TRANSMISSION

ECONOMICS OF POWER TRANSMISSION 

The cost of transmission line includes the investment and operational costs. The investments include costs of Right of  Way (RoW) , transmission towers , conductors , insulators and terminal equipment . The operation costs include mainly the cost of loses.

             The Characteristics of insulators vary with the type of voltage upplied . For simplycity , if it is assumed that the insulater characteristics are similar for AC and DC and depend on the peak leaves of voltage applied with respect to ground, then it can be shown that for lines designed with the sane insulation leavel, a DC line can be carry as much power with two conductors (with positive and negative polarities with respect to ground)as an AC line with 3 conductors of the same size. This implies that for a given power level, DC line requires less RoW, simpler and cheaper towers and reduced conductor and insulator costs. The power loses are also reduced with DC as there are only two conductors (about 67% of that for AC  with sane current carrying capacity of conductors).The absence of skin effect with DC is also beneficial in reducing power losses marginally. The dielectrict losses in case of power cables is also very less for DC transmission. 

                   The Corona effects tend to be less significant on DC donductors then for AC and these also leads to the choice of economic size of conductors with DC transmission. The other factors that influence the line costs are the costs of compensation and terminal equipment. DC lines not required compensation but the terminal equipment costs or increased due to the presence of converters and filters