Phase-shifting transformer system

A phase-shifting transformer system for applying a desired phase shift to the voltage on a transmission line of a power system, comprising:

• a series transformer with mutually magnetically coupled series and excited windings, the series winding for coupling in series with the transmission line;
• a regulating transformer with mutually magnetically coupled exciting and regulating windings, the exciting winding for receiving power from the transmission line, and the regulating winding having two opposing ends with plural taps therebetween;
• and
• a thyristor-augmented switching network coupling together the regulating winding of the regulating transformer with the excited winding of the series transformer, with the switching network having a load tap changer for selectively coupling one of the plural taps of the regulating winding with a neutral ground potential, and an openable reversing switch for selectively coupling either end of the regulating winding with the series transformer excited winding, with at least one of the load tap changer and the reversing switch being augmented by at least one thyristor valve for conducting full load current therethrough as required by the power system during application of the desired phase shift and at least until a new steady-state condition is reached, positions of the load tap changer and reversing switch establishing a nominal phase-shifting voltage level on the series transformer series winding.

A method of retrofitting a phase-shifting transformer system to rapidly apply a desired phase shift to the voltage on a transmission line, comprising the steps of:

• identifying a phase-shifting transformer system requiring retrofitting which includes:
• a series transformer having mutually magnetically coupled series and excited windings, the series winding being coupled in series with the transmission line;
• a regulating transformer having mutually magnetically coupled exciting and regulating windings, the exciting winding for receiving power from the transmission line;
• and
• a switching network coupling together the regulating winding of the regulating transformer with the excited winding of the series transformer for establishing a nominal phase-shifting voltage level on the series transformer series winding;
• and
• coupling a modulator with the series transformer to modulate the voltage of the series transformer series winding about the nominal phase-shifting voltage level provided by the switching network.

A method of retrofitting a phase-shifting transformer system to rapidly apply a desired phase shift to the voltage on a transmission line, comprising the steps of:

• identifying a phase-shifting transformer sytem requiring retrofitting which includes:
• a series transformer having mutually magnetically coupled series and excited windings, with the series winding coupled in series with the transmission line;
• a regulating transformer having mutually magnetically coupled exciting and regulating windings, with the exciting winding receiving power from the transmission line;
• and
• a switching network coupling together the regulating transformer regulating winding with the series transformer excited winding for establishing a nominal phase-shifting voltage level on the series transformer series winding;
• and
• augmenting the switching network with at least one thyristor valve for conducting full load current therethrough at least during the application of the desired phase shift to the voltage on the transmission line.

A method of applying a desired phase shift to the voltage on a polyphase transmission line operating at a system frequency, comprising the steps of:

• drawing a polyphase regulating current at a regulating voltage from the transmission line;
• establishing a nominal magnitude of a shifting voltage between maximum and minmum values, the shifting voltage being in quadrature with the regulating voltage;
• changing the shifting voltage magnitude to any value between the maximum and minimum values within a single cycle of the system frequency to modify the phase shift as desired;
• and
• injecting the changed shifting voltage in series with the voltage on the transmission line.