Transmission capacity from the northern hydro to the southern nuclear regions has decreased due to the closing of reactors in the south. Power transmission is more complex than just building a fatter pipe to pour more water through. Having stable power in the south is a prerequisite to transfer hydro power from the north.
I don't understand, surely the southern grid is stabilized by interconnections to europe? I thought closing reactors would be independent of transmission. What am I missing?
They are separate grids: not synchronous, not stabilising each other. Most of the interconnections are HVDC links. Wikipedia has an article on synchronous grids of Northern Europe.
The decommissioning of several large generating stations in southern Sweden has indeed affected the effective transmission capacity from the north.
