Changing Synchronous Machine Properties

Synchronous machines are modeled by specifying the machine characteristics in the PSS/U Machine Dictionary. When you import a PSS/U raw data file into PSS/ADEPT, the synchronous machine parameters specified in the Machine Dictionary file — armature resistance, transient reac-tance, subtransient reacreac-tance, zero-sequence impedance, locked rotor impedance, and starting transformer impedance — are used. If there are no machines in the dictionary representing the given machine type, PSS/ADEPT will assign default values to the machine impedances. Refer to Appendix F to obtain the actual default values.

To change the properties for a synchronous machine:

1. Double-click the synchronous machine to select it and display the Synchronous Machine Property sheet, or, to select a synchronous machine, right-click, and choose Properties to display the Synchronous Machine Property sheet (Figure 3-51).

Notice that there are four tabs for the property sheet: Main, Impedances, Start-Up and Harmonics. The Main tab is used to enter synchronous machine charac-teristics and to establish the machine location within the network.

Users Manual Editing Shunt Devices

2. Under the Main tab, enter/select the properties for the synchronous machine:

Name: Specify a unique name for the synchronous machine on the PSS/ADEPT dia-gram. This is not the name of the node to which the machine is connected. The node name appears on the property sheet to indicate the location of the machine in the net-work. If you modify the machine name, the name of the node to which it is attached will not be affected.

Machine type: Select the type of machine from the following: Constant power, PV Machine, or Swing Source.

• A constant power machine

• A PV Machine

• A swing source

Regulated node: Node where voltage of the machine is regulated.

Connection: Specify whether the machine is wye or delta connected.

Nominal machine size (kVA): The nominal machine size is the electrical rating of the machine. This value is only used to convert pu impedances into ohms.

Nominal machine voltage (kV): Nominal voltage of the machine is either line-to-line or line-to-neutral voltage in kV, depending on the input voltage flag you selected on the Network Property sheet System tab. If no voltage is specified, the base voltage of the node where this machine is connected will be used as the nominal machine voltage.

This value is used along with the nominal machine size to convert pu impedances into ohms.

Scheduled real power consumed (kW): Enter the scheduled real power consumed in kW. This value is enabled only when a constant power or PV machine has been selected.

Scheduled reactive power consumed (kvar): Enter the scheduled reactive power consumed in kvar.

Scheduled voltage (pu of node base voltage): The scheduled voltage is the terminal voltage to be held by the machine voltage regulator. This value is entered in pu of the base voltage of the node where the machine is located.

Scheduled voltage angle: Scheduled voltage angle in degrees.

Max. reactive power output and Min. reactive power output (pu of machine rating): These fields specify the minimum and maximum reactive power output of the machine in pu of the nominal machine rating.

3. To display the synchronous machine on the diagram, click once in the Visible check box (under the Main tab) to place a check mark there.

4. To indicate that the selected synchronous machine is in service, click the In service check box (under the Main tab), which is the default setting. If In service is not checked, the synchronous machine is out of service.

5. Check the box labeled Results to display analysis results for this synchronous machine on the diagram.

6. To add the selected synchronous machine to an existing group(s), click the Groups button (under the Main tab), and click the box that precedes the group name you want.

Click the OK button to accept the assignment.

7. To add the selected synchronous machine to an existing category(ies), click the Categories button (under the Main tab), and click the box that precedes the load category you want. Click the OK button to accept the assignment.

8. Click the Impedances tab (Figure 3-52) to view the impedance properties for the syn-chronous machine.

Figure 3-52. Synchronous Machine Property Sheet: Impedances Tab

Impedance model: Select the impedance model from the available list of the following model types:

• Custom: A custom machine is a user-defined custom machine type. Enter the impedances of the machine in the fields provided on the property sheet.

Users Manual Editing Shunt Devices

• Steam turbine – large: The associated impedances for a large (several hun-dred MW round rotor machine) steam turbine will be automatically placed in the fields on the property sheet.

• Steam turbine – small: The associated impedances for a small (less than 100 MW round rotor machine) steam turbine will be automatically placed in the fields on the property sheet.

• Hydro w/ damper: The associated impedances for a hydro with damper wind-ings (salient pole machine with damper windwind-ings) will be automatically placed in the fields on the property sheet.

• Hydro w/o damper: The associated impedances for a hydro machine (salient pole) without damper windings will be automatically placed in the fields on the property sheet.

• Combustion turbine: The associated impedances for a combustion turbine will be automatically placed in the fields on the property sheet. A combustion turbine is represented as a small round rotor machine.

Based on your selection, values will be appropriately disabled on the property sheet. Synchronous machine default values were obtained from various examples found in textbooks and other technical literature for typical machines.

Rotor type: Select the rotor type from the available list:

• Round rotor – solid steel rotor

• Salient pole – gaps between poles

Based on your selection, values will be appropriately disabled on the property sheet.

Has damper windings: Indicate whether the machine has damper windings by click-ing within the box. A check mark indicates the machine has damper windclick-ings. This option is only available for custom, and hydro impedance models with a salient pole rotor type.

Reactances

• Subtransient reactance (pu): The subtransient reactance of the machine is used to determine the fault current contribution of the machine during a fault analysis. This value is specified for both the direct and quadrature axes.

• Synchronous reactance (pu): The direct and quadrature synchronous reac-tance of the machine

• Transient reactance (pu): The transient reactance of the machine is used to determine the fault current contribution of the machine during a fault analysis.

This value is specified for both the direct and quadrature axes.

Time constants

• Open circuit subtransient (sec): The time constant for the direct-axis (D-axis) and quadrature-axis (Q-(D-axis). The default is 0.35 seconds.

• Open circuit transient (sec): The time constant for the direct-axis and quadrature-axis. The default value is 7.0 seconds.

Impedances

• Armature resistance (pu): Armature resistance is the machine's resistance at synchronous speed.

• Negative sequence resistance (pu): The negative sequence resistance of the machine. Resistance is given in per unit on the machine kVA base.

• Locked rotor resistance and reactance (pu): The locked rotor resistance and reactance of the machine is used to determine the starting current of the machine in motor starting analysis.

• Zero sequence resistance and reactance (pu): The zero-sequence imped-ance of the machine specified in pu.

• Grounding impedance: The grounding impedance of the machine in absolute physical units (ohms).

Saturation Coefficients

• Saturation coefficients: The saturation coefficients of the machine at 1.0 pu and 1.2 pu no-load terminal voltage.

Mechanical

• Inertia constant (sec): The inertia constant of the machine in seconds.

9. Click the Start-Up tab (Figure 3-53) and enter/select the start-up properties for the syn-chronous machine.

Users Manual Editing Shunt Devices

Figure 3-53. Synchronous Machine Property Sheet: Start-Up Tab

Use the Start-Up Property sheet to specify the autotransformer data that are used dur-ing the motor start analysis.

Use autotransformer: You can connect the starting motor with a series-connected autotransformer starter (starting compensator) to reduce the motor in-rush current.

Click the Use autotransformer check box to place a check mark there. If you do not select the series start-up autotransformer, the motor representation starts with full volt-age applied to the terminals.

Starting transformer resistance and Starting transformer reactance (pu): The autotransformer impedance is specified on the base of the machine and defaults to 0.0.

Starting transformer tap (pu): Specify the tap position of the auto transformer. The tap is assumed to be on the machine side and defaults to a nominal ratio (1.0).

10. Click the OK button to accept your changes to all of the synchronous machine