Two windings transformer

The `com.powsybl.iidm.network.TwoWindingsTransformer`

interface is used to model a two windings power transformer.
A two windings power transformer is connected to two voltage levels (side 1 and side 2) that belong to a same substation.
A ratio tap changer and/or a phase tap changer can be associated with a two windings power transformer.

Attribute | Type | Unit | Required | Default value | Description |
---|---|---|---|---|---|

id | string | - | yes | - | Unique identifier of the transformer |

name | string | - | yes | - | Human-readable name of the transformer |

double | yes | - | The nominal series resistance at the side 2 of the transformer | ||

double | yes | - | The nominal series reactance at the side 2 of the transformer | ||

double | S | yes | - | The nominal magnetizing conductance at the side 2 of the transformer | |

double | S | yes | - | The nominal magnetizing susceptance at the side 2 of the transformer | |

double | kV | yes | - | The rated voltage at side 1 | |

double | kV | yes | - | The rated voltage at side 2 | |

RatedS | double | MVA | no | - | The normal apparent power |

Two windings transformers can also have current limits defined for each end.

For a two windings transformer, the normal apparent power shall be identical at both sides 1 and 2.

Two windings transformer are modeled with the following equivalent model:

With the series impedance and the shunt admittance and the voltage ratio and the angle difference and potentially parameters from the current step of a ratio tap changer and/or a phase tap changer, we have:

Using the above notation, the equations of the two windings transformer, in complex notations, are as follow:

This example shows how to create a two windings transformer in the network:

```
TwoWindingsTransformer twoWindingsTransformer = substation.newTwoWindingsTransformer()
.setId("TWT2")
.setName("My two windings transformer")
.setVoltageLevel1("VL1")
.setVoltageLevel2("VL2")
.setNode1(1)
.setNode2(2)
.setR(0.5)
.setX(4)
.setG(0)
.setB(0)
.setRatedU1(24)
.setRatedU2(385)
.add();
```

This extension is used to model the Vector Group of a two windings transformer. The phase angle clock is modeled at side 2 of a two windings transformer. The voltage phase angle displacement is represented with clock hours. The valid values are 0 to 11.

Attribute | Type | Unit | Required | Default value | Description |
---|---|---|---|---|---|

PhaseAngleClock | int [0-11] | hours | yes | - | The voltage phase angle displacement |

```
transformer.addExtension(TwoWindingsTransformerPhaseAngleClock.class, new TwoWindingsTransformerPhaseAngleClock(transformer, 3));
```