To supply that capacity, high speed trains are fed with 25,000 Volt (25 kV) AC (50 Hz). High speed trains have a maximum capacity of 25,000,000 Watts (25 MegaWatts). When the HSL becomes operational, the Netherlands will be connected to the European network of high speed lines, for which an overhead wire current of 25 kV AC has been agreed.

Trains using both the regular Dutch network and the new European network must be able to switch between the two systems. This switching occurs in so-called current sluices. In addition, the introduction of a new current system requires special attention to possible electrical interference that might be caused by the new system.

In two places on the HSL route, Zevenbergschen Hoek and Bleiswijk/Zoetermeer, special substations have been built to supply the HSL with power. The current from the national grid of 150,000 Volts (150 kV) is transformed to the 25 kV needed for the HSL. These substations are the power points for the HSL.

To guarantee the most efficient transport of 25kV current to the trains, the HSL uses a so-called Auto Transformator System (AT system). There are three of these AT stations between Amsterdam and Rotterdam, and four between Rotterdam and the Belgian border. These stations make sure that any current lapse in the overhead wire is boosted back to 25 kV. The AT stations are fed from the substations by the ‘negative feeder’ hanging from the overhead wire masts. As a result, the current is practically constant on the entire route.

In the Netherlands, both the domestically operating high speed shuttle trains and the international high speed trains to Belgium/Paris travel alternatively on regular tracks and the HSL track. This means that sometimes they are supplied with 1,500 Volts DC and sometimes with 25,000 Volts AC. Where the high speed line connects with existing track, the trains must switch between currents. This takes place in so-called current sluices.

A current sluice is current-free and at least 400 metres long. Before entering the sluice, a train must lower its 1.5 kV pantograph (that is, the current collector, or the bow between the train and the overhead wire) and after the lock the train can raise its 25 kV pantograph (or vice versa). Inside the lock, the train receives no power, which means that it must enter the lock with a certain speed to prevent it coming to a standstill in the lock.

The current sluices are only recognisable by the great number of overhead wires. They are situated near the trains stations of Hoofddorp, Rotterdam North, Barendrecht, Breda Zevenbergschen Hoek and Breda West. These are the places where the HSL interlinks with existing tracks.