You are here: Database Technical Reference > Generator Data

Generator Data

This dialog box includes the following areas and tabs:

Figure 1: Generator Data Dialog Box

Connection Information

Option Description
ID Name Uniquely identifies the generator. This ID name can be up to 16 characters long. The names default to GEN-1, GEN-2, GEN-3... as you enter new generators on the one-line, but you can change those names to make them more descriptive if needed.
To Bus The bus to which the generator connects, which must already exist on the one-line. You must be careful that the To Bus has approximately the same base kV as the generator. For your reference, the To Bus base kV is displayed next to the bus name.
Conn

This specifies the type of connection of the generator windings. This affects the symbol of the generator in the one-line. The options are:

D: Delta connection

Y: Wye connection

YG: Wye connection with grounded neutral

For wye-grounded connections, you can attach CTs or relays to the ground as shown in the figure below.

 

Figure 2: Wye-grounded Connections

Specifications

Option Description
Rated kV Generator rated kV.
MVA Generator nominal MVA. Generators may be represented as a group or individually.
Type

Generator type. This value is for reference only except for HG and SYN-SP types, which have their momentary reactances determined by X’dv.

    • IND - Induction
    • SYN-DP - Distributed pole synchronous
    • SYN-SP - Salient pole without amortisseur winding
    • SYN-SPA - Salient Pole with amortisseur winding
    • SYN-COND - Condenser
    • HG w/o A - Hydro generator without amortisseur winding (same as SP)
Power Factor Generator operating power factor. This value is for reference only and does not affect analysis.
Efficiency Generator operating efficiency. This value is for reference only and does not affect analysis.
RPM Revolutions per minute of the machine. This value is for reference only and does not affect analysis.
X/R Generator reactance to resistance ratio, which is used to determine resistance values in short circuit studies. Typical range is 30-150 for most generators greater than 10 MVA.
Calculate Fills in a representative computed value for the X/R field, based on ANSI C37.010. You can override this value by typing in a different number.
GSU Transformer This field is available only when you configure your system to IEC short circuit. If the generator has a unit substation, then the ID name of the unit transformer is specified in this field. This association is required in order to implement the impedance correction on the generation station unit (GSU) or power station unit (PSU).

DC Generator Specifications

Figure 3: DC Generator Specifications Tab

Option Description
Rated kV Name plate rated voltage in kV.
kW Name plate (rated) power in kW.
RPM Rated speed in revolutions per minute.
Efficiency Efficiency in per unit.
R (armature) Internal resistance of the DC generator in ohms.

Power Flow

Figure 4: Power Flow tab of Generator Data Dialog Box

Option Description
Model

Generator bus type used in modeling the power flow simulation. When you select a particular model, those fields that do not apply become unavailable.

    • Swing - A swing bus holds the bus voltage and angle constant. To do this there cannot be limits on the amount of MW or MVAR the swing machine can accept or provide. (See Swing Sources.)
    • PV - Constant power, constant voltage generator. This is also known as a regulated generator. This model tries to hold a user-specified bus voltage within generator MVAR limits.
    • PQG - Constant power, constant var generator. This is also known as an unregulated generator. This model holds the MVAR generation within given voltage limits.
Ctl kV PU Desired control voltage for a regulated generator (PV). The generator will try to control the voltage at the controlled bus to a given value. If the generator bus is the swing bus, this voltage serves as the reference voltage. The voltage is entered in per-unit.
Ctl Angle Controlled angle is used only when a generator is designated as a swing bus. The value is entered in degrees.
Ctrl Bus

For a PV generator (regulated), the bus that is to be controlled to the control voltage. If this field is blank in the database, EasyPower fills it in with the name of the bus listed in the To Bus field. (Note that this does not take effect until you accept it by clicking OK to close the database dialog box.)  This field is ignored if the Model is set to Swing.
MW Generator output MW. This may be actual operating or a rated value. This applies only to a PV or PQG generator.
MVAR Generator output MVAR. This is only used when the generator is a constant power, constant var (PQG) machine or when a PV generator MVAR limit has been reached and the machine automatically switches to PQG.
MVAR Limits Minimum and maximum MVAR limits for regulated generators (PV). The generator will switch to type PQG if these limits are violated. If there is only one swing generator (Model = “Swing”) on a bus, it should not have any MVAR limits. If there are more than one swing generators on a bus, at least one of them must be unlimited.

DC Generator Power Flow

Figure 5: DC Generator Power Flow tab

Option Description
Model

DC generators have three control modes:

  • Swing (Regulated): The voltage is controlled directly on the terminal of the generator. A regulated DC generator has the ability to be the single source that enables a system to enter power flow and solve the system.
  • Swing (Un-Regulated): The voltage is held constant internally as a Thevenin source. The terminal of the generator changes with loading. An un-regulated DC generator has the ability to be the single source that enables a system to enter power flow and solve the system.
  • Constant Power: The generator is modeled as a constant power generator, similar to a PQ generator in the AC power flow. A constant power DC generator DOES NOT have the ability to be the single source that enables a system to enter power flow and solve the system. To enter power flow focus, at least one other source must be modeled that supplies the system with stiff internal or external source.

Impedance

Figure 6: Impedance Tab of Generator Data Dialog Box

Option Description
X”dv Subtransient reactance in percent on generators MVA base. Most synchronous generators have subtransient reactances in the 9-20% range1Short Circuit Calculations, General Electric , GET 3550. . The subtransient reactance is used for ½ cycle, 5 cycle and 30 cycle short circuit calculations in accordance with ANSI Standards.
X’dv Transient reactance in percent on generators MVA base. This value typically ranges from 15-30%. The transient reactance is not used in ANSI standard calculations except for hydro and salient pole generators without amortisseur windings (Xpu = 0.75X’).
X0v Zero sequence reactance in percent on generators MVA base. This value may range from 3-15% for typical generators. Zero sequence values are used in all ground fault calculations.
Xlr Locked rotor impedance for induction machines. When actual data is not available, use 16.7%.
Ground R

Generator neutral ground resistance in ohms. This is the most common method of grounding generator neutrals and is usually given in amperes. The impedance is found from the following equation.

R = Vln / I

If the generator is grounded through a grounding transformer with a secondary resistance, this resistance must be converted to the primary winding. If you know the Amp value for the resistor, you can enter the amp value in the Amp Class field and use the Calculate button to find the resistance.
Ground jX Generator neutral ground reactance in ohms.
Amp Class This is the current in amps through the ground impedance at the rated voltage. You can enter data in this field directly in Amps or calculate it based on the voltage and ground impedance R +jX using the Calculate button.

TCC

Figure 7: TCC tab of Generator Data dialog

Option Description
Plot Generator Decrement Curves

You can plot short circuit decrement curves “with” and “without” excitation field forcing for comparison purposes.

  • Without Field Forcing: Plots TCC for “without field forcing” option.
  • With Field Forcing: Plots TCC for “with field forcing” option.
  • Maximum Plot Time: The amount of time in seconds that the generator can sustain overcurrents without exceeding safe temperature limits.
Synchronous
Xd Synchronous reactance of the generator, expressed as a percent.
T”d Direct axis sub-transient short circuit time constant.
T’d Direct axis transient short circuit time constant in seconds.
Ta

Armature time constant in seconds.

A typical generator datasheet will provide the Ta value. However, some manufacturers may not provide Ta in the datasheet. The armature time constant is associated with the rate of change of dc current in the stator when the generator is subjected to a 3-phase fault. Ta for different types of generators is provided in the book “Power System Control and Stability,” by Paul M. Anderson and A. A. Fouad, IEEE Press, 1994.

Ta = (Ld’ + Lq) / 2r

Where Ld’ is the d axis transient inductance and Lq is q axis inductance. A typical value of Ta is 0.15 seconds for fault on the machine terminal.

Prabha Kundur’s book “Power System Stability and Control”, McGraw-Hill, 1994, provides the following equation for Ta:

Ta = (Ld” + Lq”) / 2/ Ra

Typical value for Ta lies between 0.03 and 0.35s.
Forcing Field

Forced excitation current at a given load expressed as per unit value of field current at no load, Ifd0.
Thermal Damage Curve

This section allows you to plot “I^2t” thermal damage curve for the generator.

Plot Thermal Damage Curve Select this check box to enable plotting of the damage curve and to enter data for this section.
I2t Value This defines the (I^2)t line for the damage curve. I is in per-unit of generator rated current and t is in seconds. If I2t Value is 20, then the extrapolated damage curve line would intersect with the FLA of the generator at 20 seconds.
Plot From/To The damage curve is drawn on the TCC plot within these values as the lower and upper limits in seconds.

Harmonics

Use the Harmonics tab to indicate whether this equipment item is introducing harmonics into your power system.

Figure 8: Harmonics Tab

Option Description
Resistance Factor

EasyPower offers two methods for calculating RH:

  • Resistance varying with a power of the harmonic (R-EXP):

    • RH = RFund * H R-EXP

  • Resistance varying with a percent eddy current factor (%ECF):

    • RH = RFund * (1+ECF*H2)/(1+ECF)

EasyPower defaults all skin effect correction to R-EXP and a value of 0.5.

Typical Resistance Correction Factors
  R-EXP %ECF

Transformer

0.5-1.0

1.0-3.0

Utility

0.0-0.8

    -

Generator

0.3-0.6

    -

Line/Cable

0.5

    -

Reactor

0.5-1.0

0.8-3.0

Motor

0.2-0.4

    -
Fundamental Amps

Use to set the fundamental amps. The options are as follows:

  • Equipment Rating sets Fundm Amps to the equipment rating of the item described in the Specifications tab. 
  • User Specified activates the Fundm Amps field, enabling you to specify a value. 

To use fundamental current calculated by power flow, select Calculated from Power Flow in the Summation Fundamental Voltage area of the Harmonics Options > Control dialog box.

Stability 1

Figure 9: Stability 1 Tab

Generator Model

Option Description
Enable Generator Model Enables stability data entry for the generator model.
Mfr Provides a list of generator manufacturers available in the device library. If the desired manufacturer is not listed in the device library, you can add it to the library.
Type Generator types available from the manufacturer chosen in the Mfr field above. If the desired type is not listed, you can add it to the library.
Model Lists available generator models in the library.
Lib Populates generator data from the library.

Exciter Model

Option Description
Enable Exciter Model Enables stability data entry for the exciter model.
Mfr Provides a list of exciter manufacturers available in the device library. If the desired manufacturer is not listed in the device library, you can add it to the library.
Type Exciter types available from the manufacturer chosen in the Mfr field above. If the desired type is not listed, you can add it to the library.
Model Lists available exciter models in the library.
Lib Populates exciter data from the library.

Governor Model

Option Description
Enable Governor Model Enables stability data entry for the governor model.
Mfr Provides a list of governor manufacturers available in the device library. If the desired manufacturer is not listed in the device library, you can add it to the library.
Type Governor types available from the manufacturer chosen in the Mfr field above. If the desired type is not listed, you can add it to the library.
Model Lists available governor models in the library.
Lib Populates governor data from the library.

For details on the parameters, see Dynamic Stability . For information about the library, see EasyPower Device Library.

Stability 2

Figure 10: Stability 2 Tab

Stabilizer Model

Option Description
Enable Stabilizer Model Enables stability data entry for the stabilizer model.
Mfr Provides a list of stabilizer manufacturers available in the device library. If the desired manufacturer is not listed in the device library, you can add it to the library.
Type Stabilizer types available from the manufacturer chosen in the Mfr field above. If the desired type is not listed, you can add it to the library.
Model Lists available stabilizer models in the library.
Lib Populates stabilizer data from the library.

For details on the parameters, see Dynamic Stability . For information about the library, see EasyPower Device Library.

Location

See Location for more information.

Imported Data

This tab is read-only and appears only if you have imported data from an SKM Data Format file. See Importing an SKM Format File for more information.

Comments

See Comments for information.

Hyperlinks

See Hyperlinks for information.

More Information

Database Technical Reference  
     

www.easypower.com

EasyPower, LLC

7730 SW Mohawk St.

Tualatin, OR 97062

(503)655-5059

techsupport@easypower.com

feedback@easypower.com

EasyPower Version 9.7

Copyright © 1991-2016 EasyPower, LLC. All Rights Reserved.

Help was last updated on 2/8/2016