Manapouri is not stranded from the National Grid. There is a high voltage AC line from Manapouri to Bromley(Christchurch) with a tap point in the Twizel switch-yard. Manapouri electrons destined for the North Island via the Benmore HVDC link can travel via lines connecting Twizel OHau C and Benmore.
In a future Tiwai-less situation there is insufficient capacity in the system to carry the electrons north if both Manapouri and the Clutha stations are operating at full throttle.
Transpowers capacity constraint removal project does not involve another line of towers marching across the landscape.. Existing lines will have their capacity increased by strengthening towers and upgrading the conductor plus switch yard upgrades.
Boop boop de do
Marilyn