Three windings transformer

The com.powsybl.iidm.network.ThreeWindingsTransformer interface is used to model a three windings power transformer. A three windings power transformer is connected to three voltage levels (side 1, side 2 and side 3) that belong to the same substation. We usually have:

  • Side 1 as the primary side (side with highest rated voltage)
  • Side 2 as the secondary side (side with the medium rated voltage)
  • Side 3 as the tertiary side (side with the lowest rated voltage)

A Ratio Tap Changer and/or a Phase Tap Changer can be associated to all three sides of a three windings power transformer. Only one Tap Changer (either ratio or phase tap changer) is allowed to be regulating on the equipment at a given time.

Characteristics

Attribute Type Required Default value Description
Leg1 ThreeWindingsTransformer.Leg yes - The leg at the primary side
Leg2 ThreeWindingsTransformer.Leg yes - The leg at the secondary side
Leg3 ThreeWindingsTransformer.Leg yes - The leg at the tertiary side


Attribute Type Unit Required Default value Description
id string - yes - Unique identifier of the transformer
name string - yes - Human-readable name of the transformer
RatedU0 double kV yes - The rated voltage at the star bus


Three windings transformers can also have current limits defined for each leg.

Leg

ThreeWindingsTransformer.Leg is a nested interface used to model a leg of a three windings power transformer.

Characteristics

Attribute Type Unit Required Default value Description
Terminal Terminal - yes - The terminal the leg is connected to
R double yes - The nominal series resistance specified at the voltage of the leg
X double yes - The nominal series reactance specified at the voltage of the leg
G double S yes - The nominal magnetizing conductance specified at the voltage of the leg
B double S yes - The nominal magnetizing susceptance specified at the voltage of the leg
RatedU double kV yes - The rated voltage
RatedS double MVA no - The normal apparent power

For the leg of a three windings transformer, the normal apparent power shall be identical at both sides (network side and star bus side).

Model

Three windings transformers are modeled with three legs, where every leg model is electrically equivalent to a two windings transformer. For each leg, the network bus is at side 1 and the star bus is at side 2.

Power line model

Examples

This is an example of how to create a new ThreeWindingsTransformer in the network:

ThreeWindingsTransformer threeWindingsTransformer = substation.newThreeWindingsTransformer()
    .setId("TWT3")
    .setName("TWT3Name")
    .setRatedU0(132)
    .newLeg1()
        .setVoltageLevel("VL1")
        .setNode(11)
        .setR(17.424)
        .setX(1.7424)
        .setG(0.00573921028466483)
        .setB(0.000573921028466483)
        .setRatedU(132.0)
        .add()
    .newLeg2()
        .setVoltageLevel("VL2")
        .setNode(22)
        .setR(1.089)
        .setX(0.1089)
        .setG(0.0)
        .setB(0.0)
        .setRatedU(33.0)
        .add()
    .newLeg3()
        .setVoltageLevel("VL3")
        .setNode(33)
        .setR(0.121)
        .setX(0.0121)
        .setG(0.0)
        .setB(0.0)
        .setRatedU(11.0)
        .add()
    .add();

Extensions

Phase angle clock

This extension is used to model the Vector Group of a three windings transformer. The phase angle clock could be modeled at leg 2, leg 3 or both legs 2 and 3 and of a three windings transformer (network side). The voltage phase angle displacement is represented with clock hours. The valid values are 0 to 11.

Attribute Type Unit Required Default value Description
PhaseAngleClockLeg2 int [0-11] hours yes - The voltage phase angle displacement at leg 2
PhaseAngleClockLeg3 int [0-11] hours yes - The voltage phase angle displacement at leg 3
transformer.addExtension(ThreeWindingsTransformerPhaseAngleClock.class, new ThreeWindingsTransformerPhaseAngleClock(transformer, 10, 1));