https://phys.org/news/2018-06-hybrid-overhead-linesmore-power-lines.html

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. To minimise interference effects associated with the higher transmission capacity, such as corona humming and electric fields, we determined the best voltage and tower geometry using test lines under various real-world conditions both in the laboratory and in the field," says project lead Christian Franck, Professor at the ETH Zurich's Institute for Power Systems and High Voltage Technology.

Many advantages, but acceptance is not a given