Investigations into the upgrading of existing HVAC power transmission circuits for higher power transfers using HVDC technology

Cost effective higher current rated power electronic technology makes possible the conversion of high voltage alternating current circuits for high voltage direct current employment. This strategy is promoted so as to yield greater power transfers by using the same physical power line and installed conductor cross sectional area. This idea was shared and discussed by study committee B4 at the 2004 proceedings of Cigre in Paris, France. Here study committee working group members reported on the tri-pole proposal of using one phase of the conventional AC line as the positive pole, another phase as the negative pole and the remaining third phase to be periodically swapped between positive and negative poles; yielding almost 2,5 times the power transfer capability of the HVAC line. Along a similar path, the paper reports on Eskom's initial investigation into recycling two of the existing 400 kV lines emanating from Matimba power station. Additional 1800 MW thermal generation is planned alongside the existing 3600 MW power station. A known constraint is the acquisition of additional power line servitudes to evacuate the increased power generation. The real estate area surrounding Matimba power station is emerging as prime investment for environmentally sensitive international investors