Quadrature booster

A phase angle regulating transformer, phase angle regulator (PAR, American usage), phase-shifting transformer, phase shifter (West coast American usage), or quadrature booster (quad booster, British usage), is a specialised form of transformer used to control the flow of real power on three-phase electric transmission networks.

[1] Where parallel circuits with different capacities exist between two points in a transmission grid (for example, an overhead line and an underground cable), direct manipulation of the phase angle allows control of the division of power flow between the paths, preventing overload.

[2] Quadrature boosters thus provide a means of relieving overloads on heavily laden circuits and re-routing power via more favorable paths.

The shunt unit has its windings connected across the phases, so it produces output voltages shifted by 90° with respect to the supply.

(Note that the values used here are hypothetical; the actual phase angle and transfer in load would depend upon the parameters of the quadrature booster and the transmission lines.)

The installation of the phase shifting transformers was necessary in order to regulate and control the flow of green electricity from Germany.