ETAP Generator Start-Up

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ETAP PowerStation 4.0

User GuideCopyright 2001

Operation Technology, Inc.All Rights Reserved

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Chapter 18

Generator Start-Up

The PowerStation Generator Start-Up Analysis is a special feature of the PowerStation Transient Stability program. This type of analysis is needed for nuclear generation plants and other special conditions whenthe connection to a power grid is lost and recovery of the power supply to some critical loads ismandatory. In such cases, a cold stand-by generator is started under an emergency condition goesthrough acceleration and load acceptation stages, and finally settles down to a steady-state.

A comparison of the results from the PowerStation Generator Start-Up program with the fieldmeasurement data for an actual system is shown below for the generator frequency and motor kW power.

Operation Technology, Inc. 18-1 ETAP PowerStation 4.0


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Generator Start-Up Study Case Editor

18.1 Study Case EditorThe Generator Start-Up Analysis is part of the PowerStation Transient Stability program. To run agenerator start-up analysis, you need to be in Transient Stability mode. The functions of all buttons onthe Transient Stability Toolbar and the Study Case Toolbar stay the same as when you are performing atransient stability study. Here is a list of the additional settings that are required to run a generator start-up analysis. These settings are done in the Transient Stability Study Case Editor.

Time StepBecause of the complexity involved in a generator start-up analysis, many differential equations need to

be solved. To ensure the solution accuracy, it is recommended that you use a smaller value for simulationtime step, for example, 0.0003 second. Consequently, a relatively large value can be used for the plottime step, say 100.



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Generator Start-Up Study Case Editor

Event & ActionWhen performing a generator start-up analysis, it is very import to remember that starting the generatorshould be the first action to take place. The generator start action is specified in the Transient StabilityStudy Case Editor, as shown below. To do this, you need to create a time event and add one action with

the Device Type specified as Generator and the Action type as Start.

Dynamic ModelThe generator start-up analysis requires all system components to be modeled with frequency

dependency. This is done by checking the Frequency Dependent Models for Network, Motors, &Generators box in the Dyn Model page of the Transient Stability Study Case Editor.



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Generator Start-Up Calculation Methods

The equivalent circuit for this model is illustrated below.

- + L fd - Lad Ll

Rd

R fd

L fd

V fd

Ld

Lad

Ra

id

q

V d

+

-

Direct-Axis Equivalent Circuit

V

d Ll + -

Laq

Ra

iq Lq

Rq

Direct-Axis Equivalent Circuit



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Turbine Governor ModelsPractically any type of turbine-governor model in PowerStation can be used in the generator start-upstudy, provided there are no other special control functions required. For example, shown below is ahydro turbine and speed governor model. It includes water tunnel and penstock dynamics and a very

complex gate opening control scheme.



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Exciter/AVR ModelsThe exciter/AVR system requires special controls in the generator start-up study. For example,exciter/AVR model ST1D is shown below and can be used for the generator start-up analysis. This modelincludes a special field flashing circuit to supply the initial DC excitation voltage to the generator field

winding. A voltage per Hz relay is also included to switch the excitation source from the initial DCsource to the normal source once the generator has built up enough voltage.



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Induction Machine ModelInduction machines, which are accelerated during generator start-up process, should be modeled by theirfrequency dependent circuit models. PowerStation automatically uses the frequency dependent circuitmodels that are selected from the Motor CKT Model Library Quick Pick Editor inside the Induction

Machine Editor. All four types of induction machine circuit models, namely Single1, Single2, DBL1, andDBL2, can be used as the frequency dependent models for a generator start-up analysis.

Synchronous Motor ModelsAccelerating synchronous motors in the system are modeled with their LR models same as inductionmachines with frequency dependent circuit models, since they behave like induction motors during start-up.

Other ComponentsOther system components such as transforms, lines, and cables are modeled the same way as in transientstability studies except for the fact that the program will adjust their impedance according to the systeminstantaneous frequency.



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Generator Start-Up Output Reports

18.3 Output ReportsThree types of output reports are available for a generator start-up analysis, and they are text report, one-line display, and plots. Please refer to the Transient Stability chapter for more information on how toaccess and manage the output reports.

Text ReportThe text report for the generator start-up analysis is the same format as the transient stability analysis.

One-Line DisplayThe one-line display for the generator start-up analysis is the same format as the transient stabilityanalysis.

PlotsThe plots for the generator start-up analysis are the same format as the transient stability analysis.

Some sample plots from a generator start-up analysis are shown here.


Documents

ETAP Generator Start-Up