Complex sentence: Until completion of the Montpellier-Perpignan LGV, however, the connection will require dual voltage trainsets as that portion is currently electrified to 1,5 kV DC, not 25 kV 50 Hz.
Split into simpler sentences: Until completion of the Montpellier-Perpignan LGV, however, the connection will require special trainsets. That portion of the line is currently electrified to 1,5 kV DC, not the standard 25 kV 50 Hz.