Quadrature booster

A phase shifting transformer, also cross- regulating transformer, is a special power transformer, which serves in the field of AC electric power grids to control the electrical load flow in parallel lines specifically. Applications are found these transformers in high voltage networks, such as the 220 ​​kV or 380 kV voltage level. The apparent power is up to 1,500 MVA.

The technical improvements in the field of power electronics phase shifting transformers are replaced in power supply networks increasingly Unified Power Flow Controller ( UPFC ), which allow a better control of the power flows assets.

General

In contrast to the common use of transformers, the implementation of AC voltages to different voltage levels, these transformers are used as a phase shifter so as to affect the performance of an electric line, such as a transmission line, selectively. If multiple lines are routed on different paths between two switchboards or substations, can be determined by means of phase shifting transformer, as the power is distributed. This is especially important if the existing lines are assigned to different voltage levels have significantly different transport services or overhead lines are combined with underground cables.

Construction

A phase- shifting transformer is as represented schematically in the illustration, a series transformer, similar to a current converter and an exciting transformer ( " shunt transformer " ), via which by means of a level switch, a certain phase shift can be adjusted.

In the commonly used three-phase alternating current for each phase conductor a series and a variable transformer available. The AC voltage is supplied to the left via the connections L1, L2 and L3. Via the control transformer, a voltage is tapped off per phase switches, which is offset from the line voltage with respect to ground by 90 ° and on the illustrated right series transformer means vector addition ' carries the phase-shifted voltage to a to L1 ', L2 ' and L3. This type of load flow influence is referred to as cross- compensation, in contrast to the longitudinal compensation using reactors or capacitor banks, as it is found in the static reactive power compensation ( SVC). Since the power flow can be effected by the phase shift transformer in both directions, " input " or " output" can in principle be selected as desired.

The adjustment of the phase-shifted voltage is different depending on the type. It is typically in the range of ± 10 ° and may be up to 30 ° in particular embodiments. In real phase -shifting transformers (there are several circuit variations ) are additional components used, such as an Advanced Retard Switch ( ARS ) on the series transformer to sign reversal of the phase angle.

Due to the phase shifting transformer is created in the mesh (loop), which is formed in the simplest case by two parallel lines, an additional load flow, which is the external load flow superimposed by the two lines. This leads, depending on the selected phase shift to a reduction or increase of the load flow in the individual lines. Upon reversal of the external power flow has to be inverted, while maintaining the power distribution, the phase position.

Application

In single phase diagram shown on the right the distribution of flows between two lines is shown at different settings on the phase shifting transformer. The power supplied to the generator power and the extracted power is the same in both cases, without regard to the losses, for example, each of 100 MVA. Are exemplary numerical values ​​shifted real power measured in MW, with a given phase angle depends on the electrical properties of the phase shifter and the transmission system.

By the phase shifting transformer and the power flow so that the currents in the two lines may then be adjusted. In the left partial image, the phase angle is selected so that more than two lines, the same power of 50 MW is transmitted. In the right image, the phase angle is changed on the transformer, which are transported 27 MW on a line 73 MW and on the other line. The sum corresponds each time the total capacity of 100 MW.

In real systems occur not shown here, additional losses due to the thermal losses of the phase shifting transformer and additional line losses on the line with the larger power flow around which in this case reduces the removable power versus injected power. In addition, in real power grids usually not only two parallel lines between two substations are present, as in this simplified example, but by the meshing in a grid results in further reciprocal influences of load flows.

Installed equipment

Installed facilities are located in the 400 kV network between the Netherlands and Belgium, on the border between Germany and the Netherlands, the German grid at the substation entrance hall and the Austrian 220 - kV network of Austrian Power Grid ( APG) in the substations Ternitz substation Ernsthofen and substation Tauern.