The electrical supply demand is increasing globally. Power plants are often located near to energy sources, to minimize costs and environmental effects. These power plants often are located away from heavily populated areas or cities, therefore, transporting the electricity generated economically and efficiently is important. This is accomplished by transmitting the generated power at a high voltage. High-voltage (HVAC) is preferred for transmission purposes mainly because higher voltages are easily achievable by means of a transformer (stepping up at the power plant and stepping down at the substation).

To meet the growing demand, utilities are looking at improving the system performance by interconnecting the grid to balance the load and looking at using newer technologies (HVDC or Flexible AC Transmission Systems FACTS) for improving efficiency. The advantages of HVAC is simpler voltage transformation and easier current interruption. In some cases, it is not possible to use HVAC transmission technology, when long transmission lines (> 500 km) are involved due to voltage instability and higher transmission losses. The disadvantage of HVAC is limitations on long distance transmission, current carrying capacity, reactive power (need reactive power compensation at different locations along the transmission lines) loss, skin effect (non-uniform current distribution in conductors carrying, where most of the current is found in the conductor’s outer layers increasing effective resistance) and the Ferranti (received voltage higher than the transmitted voltage) effect. Using HVDC for transmitting power over long distances is the solution.