>> I don't think any country uses DC for power transmission.
>
>Except for a couple 0.5MV systems, you're right.

In New Zealand they have a DC system between the North Island and the South
Island. The DC is then converted to AC using Mercury Vapour Thyratrons IIRC.
I cannot recall just what the maximum power transfer capability is.

This system was necessary to transfer power between the islands as it was
too difficult to synchronise the AC power of both islands through the cables
which do have a (relatively) limited capacity IIRC.

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