Abstract: A device for connecting a tuned power transmission line to an a.c. network includes the following units that are serially interconnected in any combination: a phase transposition unit for phase shifting the voltage through an angle which is a multiple of the natural shift of voltages of opposite phases; a coupling transformer with a switchable group of connections of its windings, which matches the voltages of the tuned power transmission line and the a.c. network and effects a voltage phase shift which is a multiple of 180.degree.; and a transverse voltage regulation transformer which makes it possible to smoothly change the voltage phase shift under load.