For controlling the voltage of a transmission line, at the receiving end, a synchronous motor is used. In this application, the synchronous motor is made to run on no load and draw a leading current. The synchronous motor when used for the above purpose is called synchronous phase modifier. As the power factor of the system is improved by the action of synchronous condenser, the drop of volts from the sending to receiving end on the line is decreased and the regulation of the line is improved.