Single-phase feed-in assembly and method for supplying alternating current tracks with single-phase alternating current power

The power supply device comprises contact line sections (1,1') and one or more sub-units (2,2') for providing electrical energy for electrical rail traction vehicles. The ends (1A,1A') of the contact line sections are separated by a separation area (3). A switching unit (7) is arranged for switching a switchable autotransformer (6) such that the ends of one contact line section are connected to the low-voltage side of autotransformer and the ends of other contact line section are connected to the high-voltage side of the autotransformer. An independent claim is included for method for supplying single-phase current to contact line of alternating current tracks.