Mr. Fintan Slye:

The issue is not so much the voltage level but the technology, by which I mean whether it is AC or DC technology. There are technical limits to how much undergrounding can be achieved with AC technology. Those limits are shorter at 400 kV than at 220 kV, and shorter again at 220 kV than at 110 kV. It is not possible to run a high voltage AC circuit at 220 kV or 400 kV for the length of the North-South interconnector. To go underground one would need to move to a different technology which is HVDC technology to deliver that. The voltage has an effect on the amount that can be underground, but it is an inherent fact of AC transmission technology that there are technical limits on the amount of undergrounding that can be done at high voltages. We have looked at an underground solution, we have looked at ways to deliver that underground solution and we have determined that it is not possible to do it at AC but it is possible to do it at DC. That is the alternative that exists. That was one of the key conclusions of the international expert commission review for the Government and reported at this committee, that employing AC technology for the length of the North-South interconnector was not technically feasible.