Power output stats for the PBKA taken from wikipedia:
8,800 kW (11,801 hp) on 25 kV AC
5,160 kW (6,920 hp) on 15 kV AC
3,680 kW (4,935 hp) on DC (Doesn't specify what voltage)
So quite a difference between 25 kV and 15 kV. I'd imagine that this isn't to much of a problem between Aachen and...