Hybrid overhead lines: More power, not more power lines
Social opposition to new high-voltage lines is delaying modernisation of the power grid. Two projects of the National Research Programmes "Energy Turnaround" and "Managing Energy Consumption" have determined the optimum design of hybrid overhead lines needed to increase the capacity of the power transmission grid and, at the same time, win popular acceptance for the new technology. Unlike conventional power lines, hybrid overhead lines combine alternating current (AC) and direct current (DC) systems on the same tower instead of two AC systems. This increases transmission capacity even though the height and width of the lines remain identical, and it avoids new construction and encroachment on the landscape. However, interference caused by the weather, contamination of the AC and DC conductor cables or the distance between cables can lead to bothersome noise and electric fields. As part of the National Research Programme "Energy Turnaround" (NRP 70), a team of researchers at ETH Zurich investigated the optimal design of this hybrid system. "Hybrid overhead lines have two major advantages: their capacity is over 50 per cent higher and they are more likely to be accepted because you can upgrade existing high-voltage lines rather than build new ones.
