Power system with three-phase three-winding transformer

This tutorial describes simple steps to create a power system with a three-phase three-winding transformer

In this tutorial, one learns how to model a power system with nominal voltages of 220, 35 and 10 [kV]. This energy area is represented by loads at voltages of 35 [kV] and 10 [kV], the loads are powered from the 220 [kV] power system through a step-down three-phase three-winding transformer. As a result of the calculation, it is required to determine the magnitude of voltage at the beginning and end of each PTL.

1.  Project creation and setup

First you need to create a new project and give it a name, for example, Power system with a three-phase three-winding transformer.

In the next step, one needs to make the following settings, Fig. 1:

Setup	Value
1 Synchronization with real time	Disable
2 Simulation time	0.2 [s]
3 Integration step	0.05 [ms]
4 Sampling step	0.05 [ms]

Fig. 1 Project setup

Note

Disable parameter to set the simulation time to < 1[s]

Important

In REPEAT VISION decimal numbers are specified through a period.

Let’s start the basic steps for creating a diagram by opening the library Electronics.

2.  Three-phase voltage source creation

Add block №1 of our diagram, for this purpose we will transfer it to the workspace block Three-phase voltage source.

Note

This block represents the equivalent of the power system that powers the area.

In the properties of block №1 specify (see Fig. 2 below):

Property	Value
1 Phase-to-phase RMS voltage	230000 [V]
2 Source resistance	1 [Ohm]
3 Source inductance	0.001 [H]

Fig. 2 Properties of block №1

3.  Creation of a three-phase three-winding transformer

Add to the workspace block №2 Three-phase three-windings transformer, which is necessary to transform the supply voltage from 220 [kW] to 35 [kW] and 10 [kW].

In the properties of block №2, set the following properties (see Fig. 3 below):

Property	Value
1 Method of specifying model parameters	Specification
2 Tertiary windings connection scheme	D11
3 Nominal power	40e6 [VA]
4 Nominal voltage of secondary winding	38500 [V]
5 Nominal voltage of tertiary winding	11000 [V]
6 Nominal HV - LV short-circuit losses	1e-3 [W]
7 Nominal HV - MV short-circuit losses	220000 [W]
8 Nominal MV - LV short-circuit losses	1e-3 [W]
9 Nominal HV - LV impedance voltage	22 [%]
10 Nominal HV - MV impedance voltage	11 [%]
11 Nominal MV - LV impedance voltage	9.5 [%]
12 Nominal no load losses	54000 [W]
13 Nominal no load current	0.55 [%]

Fig. 3 Properties of block №2

Note

Leave the rest of the block properties unchanged.

Important

These properties are based on the catalog parameters of the TDTN-40000/220/38.5/11 transformer [1].

Note

As a rule, reference data for three-phase three-winding transformers show short-circuit losses for only one pair of windings (in this case, for HV and AV windings). In this case, it is permissible for other pairs of windings to indicate losses 1e-3 [W].

4.  Creating PTL 220 [kV]

In order to simulate PTL 220 [kV] power lines, which is designed to transmit electric energy and power to the transformer, let’s transfer of block №3 Three-phase series RLC branch to the workspace, set the following properties and then place and connect the blocks in accordance with the Fig. 4 below:

Property	Value
1 Branch type	RL
2 Phase resistance	18.15 [Ohm]
3 Phase inductance	0.208 [H]

Fig. 4 Properties of block №3 and its connection to the diagram

Note

The given parameters are calculated based on the design parameters of the AC 240/32 wire [1] with the length of PTL 150 [km].

5.  Creating PTL 35 [kV]

In order to simulate PTL 35 [kV], which is designed to power the load at this voltage, let’s transfer the block block №4 Three-phase series RLC branch to the workspace, set the following properties and then place and connect the blocks in accordance with the Fig. 5 below:

Property	Value
1 Branch type	RL
2 Phase resistance	10.7 [Ohm]
3 Phase inductance	0.0344 [H]

Fig. 5 Properties of block №4 and its connection to the diagram

Note

The given parameters are calculated based on the design parameters of the AC 70/11 wire [1] with the length of PTL 25 [km].

6.  Creating PTL 10 [kV]

In order to simulate PTL 10 [kV], which is designed to power the load at this voltage, let’s transfer the block block №5 [Three-phase series RLC branch](../../../../reference/blocklib/electronics/passive Elements/ElectronicThreePhaseSeriesImpedance/index.md) to the workspace, let’s set the following properties and then place and connect the blocks in accordance with the Fig. 6 below:

Property	Value
1 Branch type	RL
2 Phase resistance	2.94 [Ohm]
3 Phase inductance	9.135e-3 [H]

Fig. 6 Properties of block №5 and its connection to the diagram

Note

The given parameters are calculated on the basis of design parameters of the wire А 70 [2] at the length of PTL of 7 [km].

7.  Load creation at voltage 35 [kV]

In order to set the load with the «star» connection circuit at a voltage of 35 [kV], add the block block №6 Three-phase series RLC wye load. Let’s transfer the block of the same name block №6 to the workspace and indicate the necessary properties, and then place and connect the block in accordance with the Fig. 7 below.

Property	Value
1 Branch type	RL
2 Nominal phase-to-phase voltage	35e3 [V]
3 Three-phase active power	12e6 [W]
4 Inductive power	9e6 [VAr]

Fig. 7 Properties of block №6 and its connection to the diagram

8.  Load creation at voltage 10 [kV]

In order to set the load with the «triangle» connection circuit at a voltage of 10 [kV], add the block block №7 Three-phase series RLC delta load. Let’s transfer the block of the same name block №7 to the workspace and indicate the necessary properties, and then place and connect the block in accordance with the Fig. 8 below.

Property	Value
1 Branch type	RL
2 Three-phase active power	4e6 [W]
3 Inductive power	3e6 [VAr]

Fig. 8 Properties of block №7 and its connection to the diagram

9.  Adding a node

For the possibility of connecting the zero potential of the voltage source, add block №8 Node, for this purpose transfer the block of the same name block №8 to the workspace and specify the following properties, and then position and connect the block in accordance with the Fig. 9 below.

Property	Value
Number of output ports	2

Fig. 9 Properties of block №8 and its connection to the diagram

10.  Adding zero potential

Transfer of the same name block №9 Ground potential to the workspace to ground the zero outputs of the voltage source and load at voltage of 35 [kW].

One needs two such units, for this purpose let’s use one of the methods.

Classic transfer of the block from the library to the left

For this purpose transfer block №10 to the workspace.

Copying the block located on the workspace

For this purpose, one shall:

1. Select block №9 with the LMB;

2. Press a combination of buttons CTRL+C and CTRL+V.

Connect them to outputs block №8 and block №6. Place and connect the blocks in accordance with the Fig. 10 below :

Fig. 10 Connection of block №9 and block №10

11.  Adding sensors

In order to display the voltage signals of phases of source voltage, transformer and loads, let’s add block №11 Meter to the workspace. In the properties of block №11 specify (see Fig. 11 below):

Property	Value
1 Element	Three-phase voltage source
2 Parameter	Phase-to-neutral voltage of phase A, V
3 Gain factor	1e-3

Fig. 11 Properties of block №11

Note

Setting gain factor 1e-3 allows obtaining voltage in [kW] on the charts, which will simplify the perception of results and accelerate their analysis.

Similarly add and specify the properties for 5 more blocks Meter (see Fig. 12 below):

block №12

1. Element - Three-phase three windings transformer;

2. Parameter - Voltage of phase A primary winding, V;

3. Gain factor - 1e-3.

block №13

1. Element - Three-phase three windings transformer;

2. Parameter - Voltage of phase A secondary winding, V;

3. Gain factor - 1e-3.

block №14

1. Element - Three-phase three windings transformer;

2. Parameter - Phase-to-phase tertiary voltage AB, V`;

3. Gain factor - 1e-3.

block №15

1. Element - Three-phase series RLC wye load;

2. Parameter - Phase-to-neutral voltage of phase A, V`;

3. Gain factor - 1e-3.

block №16

1. Element - Three-phase series RLC delta load;

2. Parameter - Phase-to-phase AB voltage, V`;

3. Gain factor - 1e-3.

Fig. 12 Properties of blocks №12-16

Let’s place the blocks in accordance with Fig. 13:

Fig. 13 Connection of meters

12.  Let’s add the charts for visualization

1. Go to the Visualization tab (see Fig. 14 below);

2. Add three charts by triple clicking on the button Add located in the right lower corner.

Fig. 14 Visualization

Then perform three steps for each chart to be added (see Fig. 15 below):

1. Add one chart to output signal of blocks №11 and №12;

2. Add second chart to output signal of blocks №13 and №15;

3. Add third chart to output signal of blocks №14 and №16.

Fig. 15 Adding charts

Start calculation using the “Start simulation” button

The calculation should be successfully completed with the following message:

Modeling stopped on the solver side due to modeling time limit exceeded.

The previously created charts should now display the calculation results, which are shown in the fig. 16, fig. 17, fig. 18.

Fig. 16 Chart 1

Fig. 17 Chart 2

Fig. 18 Chart 3

13.  Analysis of calculation results

The results of simulation correspond to the theoretical dependencies - voltage losses occur in PTL and transformers when transferring the electric power from the power source to the loads. It can be viewed from the differences in amplitudes of sinusoids for voltages at the ends of PTL - at the end the line the voltage is less than at the beginning. Thus, for PT 220 [kW] voltage losses in phase A are equal to approximately 2.8 [kW], for PTL 35 [kW] – 3.3 [kW]. Losses of ACB linear voltage in PTL 10 [kW] are approximately 1.7 [kW].

14.  Conclusions

As a result of completing this tutorial you obtained the basic knowledge for creating the power system with three-phase three-winding transformer.

You have learned how to:

• set the block parameters Three-phase voltage source; Three-phase three windings transformer; Three-phase series RLC branch;Three-phase series RLC wye load;Three-phase series RLC delta load.

• use block Meter for display of block signals.

15.  Sources

---

[1] (1,2,3)

B.N. Neklepayev, I.P. Kriuchkov Electric Part of Power Plants and Substations: Reference Materials for Course and Diploma Design: Study Guide for Universities. - 4th ed., revised and suppl. - M.: Energoatomizdat, 1989. – 608 p.: ill.

[2]

Reference Book for Design of Electric Networks / Edited by D. L. Faibisovich. — M.: Publishing House NTs ENAS 2006 − 320 p. ill.