Voltage control system (10, 70) for medium voltage applications, comprising the following components: • a booster- (12, 76) and a feeder- (18, 78) transformer with respective primary and secondary winding, o wherein the secondary winding of the feeder transformer (18, 78) is electrically connected with the primary winding of the booster transformer (12, 76) in an intermediate circuit, o wherein at least one of the transformer windings (14, 22) in the intermediate circuit comprises at least two taps, wherefrom one is selectable as active tap, o wherein electrically adjacent taps are assigned to different groups (26, 28) characterised by • respective contactor switches (20, 32, 34, 36, 38, 40) which are associated to each of the taps which are selectively switchable into the intermediate circuit therewith, o wherein not more than one contactor switch (20, 32, 34, 36, 38, 40) of a group (26, 28) is switchable at the same time, • respective commutation resistors (42, 44) in electrical series connection with the taps of each group (26, 28), • a common cabinet (56, 72) wherein the aforementioned components are arranged in and • connection means (52, 54, 88) in order to connect the secondary winding of the booster transformer (12, 76) with an electrical energy supply network in that way, that the secondary winding of the booster transformer (12, 76) is in series with a transmission line that's voltage is to be controlled. • a booster- (12, 76) and a feeder- (18, 78) transformer with respective primary and secondary winding, o wherein the secondary winding of the feeder transformer (18, 78) is electrically connected with the primary winding of the booster transformer (12, 76) in an intermediate circuit, o wherein at least one of the transformer windings (14, 22) in the intermediate circuit comprises at least two taps, wherefrom one is selectable as active tap, o wherein electrically adjacent taps are assigned to different groups (26, 28) characterised by o wherein the secondary winding of the feeder transformer (18, 78) is electrically connected with the primary winding of the booster transformer (12, 76) in an intermediate circuit, o wherein at least one of the transformer windings (14, 22) in the intermediate circuit comprises at least two taps, wherefrom one is selectable as active tap, o wherein electrically adjacent taps are assigned to different groups (26, 28) characterised by • respective contactor switches (20, 32, 34, 36, 38, 40) which are associated to each of the taps which are selectively switchable into the intermediate circuit therewith, o wherein not more than one contactor switch (20, 32, 34, 36, 38, 40) of a group (26, 28) is switchable at the same time, o wherein not more than one contactor switch (20, 32, 34, 36, 38, 40) of a group (26, 28) is switchable at the same time, • respective commutation resistors (42, 44) in electrical series connection with the taps of each group (26, 28), • a common cabinet (56, 72) wherein the aforementioned components are arranged in and • connection means (52, 54, 88) in order to connect the secondary winding of the booster transformer (12, 76) with an electrical energy supply network in that way, that the secondary winding of the booster transformer (12, 76) is in series with a transmission line that's voltage is to be controlled.