1

ECEN 460 Lab 10

Transient Stability and Power System Dynamics on Small and

Medium Sized Systems

Objective:

Gain experience and insights in the use the transient stability simulation software. In this lab

transient stability simulations will be used two small systems and on a 2000 bus systems to

determine critical clearing times, to look at the impact of generator losses on system frequency

and to consider methods to prevent short-term voltage collapse.

The last part of the lab uses the PowerWorld Dynamics Studio (DS) to do interactive transient

stability type power system simulations. The free 42 bus education version of the package is

available at https://www.powerworld.com/gloveroverbyesarma.

Background on 37 Bus APL System

As was the case with the previous lab, we’ll start working with the 37bus system modeling the

fictional Aggieland Power and Light (APL) grid; its oneline is shown in Figure 1.

Figure 1: 37 Bus APL System

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Procedure for Running Transient Stability on the APL System

1. Start PowerWorld Simulator. Open the Lab10_AGL_TS case. The system has been

setup to run transient stability with several contingencies predefined for the lab. Select

Add Ons, Transient Stability to display the Transient Stability form. This will be used

throughout the lab to do the transient stability simulations. This is shown in Figure 2.

Figure 2: Transient Stability Form

2. For the first transient stability contingency, select the Sprirt69 contingency. This

contingency applies a balanced three-phase fault at time equals 1.0 seconds right at the

terminal of one of the 69 kV transmission lines going into the Spirit substation. After 0.1

seconds the fault is cleared by opening the transmission line. To do the transient stability

run, click on the Run Transient Stability button. At the end of the simulation a graph

will appear showing the time-varying generator rotor angles. Save a copy of this graph

for your report.

3 Iteratively change the time the transmission line is opened to determine the critical

clearing time for this fault (to a precision of 0.01 seconds – critical time is defined as the

longest time the fault can be applied without one of the generators losing synchronism).

The critical clearing time is the time difference between when the fault is applied (i.e.,

time = 1.0 seconds) and that largest clearing time. Save a copy of the rotor angle graph

for the critical clearing time for your report, and record the critical clearing time.

4. Change the output of the Sprit69 generator from 80 to 40 MW, and repeat step 3. In your

report comment on why such a change result in a different critical clearing time.

5. Re-open the Lab10_AGL_TS case and the Transient Stability Form. Change the

contingency to Kyle138, which simulates a fault on the 138 kV transmission line between

the Kyle and WEB substations, which is also cleared by opening the line. Again

calculate the critical clearing time for this fault, saving a copy of the graph for your

report.

6. Next, change the assumed H value for the Kyle138 generator. There are several ways to

do this. One is to right click on the generator on the oneline and select Generator

Information Dialog. On the Stability, Machine Models page change the H value from

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3.0 to 6.0. Select OK to save your change and close the dialog. Again calculate the

critical clearing time for the Kyle138 contingency. Did the change in the critical clearing

time match your expectations?

Background on the 2000 Bus TSGC System

This is the same Texas Synthetic Grid Company (TSGC) 2000 bus system you used in in

previous labs though again the operating conditions are different; its online is shown in Figure 3.

In this portion of the lab you’ll be considering some of the dynamic aspects of the system.

This is a synthetic power system model that does NOT represent the actual grid. It was developed as part of the US ARPA-E Grid Data research project and contains no CEII. To reference the model development approach, use:

For more information, contact abirchfield@tamu.edu.

A.B. Birchfield, T. Xu, K.M. Gegner, K.S. Shetye, and T.J. Overbye, "Grid Structural Characteristics as Validation Criteria for Synthetic Networks," IEEE Transactions on Power Systems, vol. 32, no. 4, pp. 3258-3265, July 2017.

Potential Coal Plant RetirementsStatusMax MWBus Number

Texas Synthetic Grid Company

Note: this grid is fictitious and doesn't

represent the real Texas grid

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WACO 1

AUSTIN 2

PASADENA 3

ARLINGTON 1

M CKINNEY 3

JACKSONVILLE 1

KYLE

M ANSFIELD

GREENVILLE 1

HOUSTON 4

CYPRESS 1

HOUSTON 90

POINT COM FORT 2

LAKE JACKSON

SILVER

ROSCOE 2

TRINIDAD 1

AUSTIN 3

EL CAM PO

LEAGUE CITY

COPPERAS COVE

CEDAR CREEK 1

COLLEGE STATION 2

PFLUGERVILLE

CEDAR PARK

ANGLETON

SHERM AN 1

WINCHESTER

LEANDER 1

ABILENE 2

KENEDY

GRAND PRAIRIE 3

SAN ANTONIO 2

M IDLOTHIAN 1

BAY CITY

CUERO 2

FAIRFIELD 1

TEXAS CITY 1

SAN ANTONIO 37

TAFT 1

SPRING 2

POOLVILLE

ALLEN 1

VICTORIA 1

SNYDER 2

SEGUIN 1SUGAR LAND 2

ALVIN

M AGNOLIA 1

BRYSON 1

KILLEEN 4

COLUM BUS

CALDWELL

LAREDO 4

CONROE 5

LAPORTE

FANNIN

TYLER 4

PARIS 2

CORPUS CHRISTI 1

DENTON 1

M ERKEL 1

WACO 2

LAREDO 1

BREM OND

DAYTON

FLUVANNA 2

BRYAN 1

KILLEEN 3

STEPHENVILLE

WINGATE

FREEPORT 1

M ISSOURI CITY 2

NEWGULF

GRANBURY 2

BURNET

GRANBURY 1

SUGAR LAND 3

WILLIS 1

SAN ANTONIO 50

KATY 2

NURSERY

NEW BRAUNFELS 1

KELLER 2

CHANNELVIEW 1

ALEDO 1

SAN ANTONIO 22

GARLAND 1

JACKSBORO 1

PANHANDLE 2

ROCKDALE 1

SAN MARCOSHOUSTON 5

BAYTOWN 1

ODESSA 1

SAN ANTONIO 1

ELMENDORF

WILLIS 2

SAVOY

PANHANDLE 4

WICHITA FALLS 1

WADSWORTH

MARBLE FALLS 2

O DONNELL 1

MCCAMEY 1

PEARSALL

CORPUS CHRISTI 3

SHIRO

PORT LAVACA

FAIRFIELD 2

SARITA 1

ARMSTRONG 1

FLORESVILLE

VICTORIA 2

GEORGETOWN 3

GLEN ROSE 1

OLNEY 1

GREGORY

GOLDTHWAITE 1

CORSICANA 2

CUSHING 1

MOUNT PLEASANT 2

DALLAS 1

GRAHAM

RICHARDSON 2

BROWNWOOD

TYLER 7

MOUNT PLEASANT 1

MT. ENTERPRISE

JEWETT 1

SAN PERLITA

AUSTIN 1

MONAHANS 1

FRANKLIN

OILTON

CHRISTINE

CHRISTOVAL

WHARTON 1

MIAMI

KERRVILLE

PALO PINTO 1

STERLING CITY 1

ROSCOE 5

DEL RIO BOERNE 2

MARION 1

BRENHAM

GALVESTON 1

LA GRANGE

BASTROP

PARIS 1

YOAKUM

RALLS 1

TEMPLE 1

LAREDO 7

SPRING 8

MCKINNEY 1

EAGLE PASS

LUFKIN 3

FREEPORT 2

HONDO

HERMLEIGHABILENE 1

ALBANY 1

ENNIS

RIESEL 1

BRIDGEPORT

KATY 3

THOMPSONS

8129

8130

8131

6078

6079

6080

563 MW

563 MW

563 MW

660 MW

660 MW

660 MW

Closed

Closed

Closed

Closed

Closed

Closed

Figure 3: TSGC Lab 10 System

Procedure for TSGC Transient Stability

1. Open up the Lab10_TSGC_GenDrop case, open the Transient Stability Form, and run the

“Gen Drop 1350 MW” contingency. This contingency simulates the loss of the largest

generator in the system, a 1350 MW nuclear power plant. This contingency does a 20

second simulation (because it is a larger case it does take a little bit of time to run the

simulation). During the simulation you’ll see a graph showing the time-varying

frequency at ten high voltage buses. At the end of the simulation you’ll see three

additional graphs. One shows the time-varying frequency at all 2000 buses in the system,

the second shows the per unit voltage magnitudes at ten high voltage buses, and the last

shows the per unit voltage magnitude at all the buses in the system. Make a note of the

lowest bus frequency and the lowest per unit bus voltage magnitude. Save a copy of the

graph showing the frequency at all the system buses for inclusion in your report.

2. Next, change the contingency to “Gen Drop 2700 MW Together.” This contingency

simulates the loss of the two largest generators in the system, consisting of two 1350 MW

nuclear power plants located at the same substation. The same four graphs are shown at

the end of the simulation. Again note the lowest bus frequency and lowest per unit bus

voltage magnitude. Save a copy of the graph showing the frequency at all buses for your

report. In your report contrast the two contingencies. Based on these two results, do the

responses seem to be proportional to the amount of generation lost?

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3. Next, change the contingency to “Gen Drop 2700 MW Separate.” This contingency also

simulates the loss of 2700 MW of generation. However, now the losses occur in two

different locations in the system (the original 1350 MW nuclear power plant from step 1

located on the Texas Gulf Coast and a total of 1350 MW of generation being supplied by

several generators at a plant in West Texas). Again note the lowest bus frequency and

lowest per unit bus voltage magnitude, and save a copy of the graph showing the

frequency at all buses for your report. In your report contrast the 2700 MW

contingencies. Which one seems to be the more severe contingency?

4. Finally, an issue that is currently confronting the electric power industry is the transient

stability impacts due to the retirements of potentially large amounts of coal generation.

For example, in the actual ERCOT system more the 4 GW of coal plant retirements have

been announced in October 2017. In this step you will briefly consider the impact of

retirements on our lab 10 synthetic grid. Using the table shown on the oneline to the east

of Texas, open at least 2000 MW of generator capacity (your choice of which ones to

open), and then rerun the “Gen Drop 2700 MW Together” contingency. Again note the

lowest bus frequency and lowest per unit bus voltage magnitude, and save a copy of the

graph showing the frequency at all buses for your report. In your report contrast the two

contingencies. To open a generator from the oneline table you will need to right-click on

a field, select Generator Dialog, change its Status to Open, and click OK. Opening

generators will change the power flow solution with the change in generation picked up

at all the other generators in the system except the ones involved in the transient stability

contingencies.

Interactive Simulations Using PowerWorld Dynamics Studio (DS)

In this portion of the lab you’ll gain experience on power system dynamics through interactive

simulations done using PowerWorld Dynamics Studio (DS).

Procedure for 42 Bus Tornado Case

1. Start PowerWorld DS, and open the Bus42_Tornado case. This runs a real-time

simulation on a 42 bus, 345 and 138 kV case in which a tornado is assumed to move

through the center of the system. Starting at ten seconds of simulation time, the tornado

rapidly outages three 345 kV lines, and also takes out the supply to a 500 MW wind farm.

Your job is to prevent the system from experiencing a blackout by shedding the least

amount of load. The oneline for this system is shown in Figure 4. If an initial contour is

not shown, right-click on a blank portion of the oneline and select Contouring. This

displays the Contour Options dialog. Just click OK to accept the defaults and display the

contur.

2. Initially just watch the simulation. To do this, select Simulation Control, Start. At ten

seconds in you’ll see a red flash due to the low voltages caused by the first tornado

induced transmission line fault. The power system should blackout at a simulation time

of about 90 seconds (with the simulation time shown at the top as seen in Figure 4). The

simulation models a simple protection system in which overloaded transmission lines are

eventually opened using an inverse time relationship (i.e., so more heavily loaded lines

trip quicker) and generators can trip because of various other protection systems. The

time variation in selected bus voltage magnitudes and frequencies is shown in two strip

chart displays as seen in Figure 4.

3. Now it is your turn. Select Simulation Control, Reset and Start. This restarts the

simulation. Since the transmission lines are assumed to have tripped and locked out so

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they cannot be reclosed (including the wind farm), in this scenario your only control

possibilities are to open up loads. You can do this either by left-clicking on the load’s red

circuit breaker symbol (if necessary zoom and pan as in PowerWorld Simulator) or by

right-clicking on the load itself and the selecting Load Dialog, which displays the Load

Information Dialog with an example shown in Figure 5. Then left-click the Open Device

button to shed the load. Try to save the system by shedding the minimum amount of

load! At any time you can pause the simulation by selecting Simulation Control, Pause.

Then select Simulation Control, Continue to continue.

Figure 4: 42 Bus Tornado Scenario

Figure 5: DS Load Dialog

4. Iterate through the scenario a number of times trying to develop an optimal strategy.

Save a copy of the display at either the end of the simulation or at the time of blackout

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with your best strategy for inclusion in your report. Just use the Windows Print Screen

function (ALT + Print Screen) to do this. Don’t spend too much time on this step, no

more than say five iterations. Just do the best you can!

Procedure for 2000 Bus TSGC Tornado Case

1. Start PowerWorld DS, and open the Lab10_TSGC_DS case. This runs a real-time

simulation on a modified version of the 2000 bus TSGC system. The scenario here is

again a tornado moving through the system, this time by a 500 kV substation west of Fort

Worth, Texas. Starting at ten seconds of simulation time, the tornado rapidly outages

three 500 kV lines. Your job is again to prevent the system from experiencing a blackout

by either changing generation (which may involve opening the generator) or shedding the

least amount of load. The oneline for this system is shown in Figure 6. If an initial

contour is not shown, right-click on a blank portion of the oneline and select Contouring.

This displays the Contour Options dialog; click OK to add the contour.

Figure 6: DS TSGC Scenario Oneline

2. Again initially just watch the simulation selecting Simulation Control, Start. The first

line will open at ten seconds. The power system should blackout at a simulation time of

about 100 seconds. This simulation also models a simple protection system in which

overloaded transmission lines are eventually opened using an inverse time relationship

(so more heavily loaded lines trip quicker). The time variation in selected bus

frequencies is shown in the strip chart display.

3. Now try to prevent the blackout for the 200 second duration of the simulation. To restart

the simulation select Simulation Control, Reset and Start. In this scenario you can

either change the outputs of the generators, open the generators, or change the status of

the loads. To change the generation, right-click on the magneta generator MW fields

shown on the oneline. This displays the Generator Information Dialog with an example

shown in Figure 7. To change the MW setpoint for the generator, enter a value into the

Power Setpoint (MW) field that is in the range between the minimum and maximum

MW limits. Then click the Change Real Power (MW) Setpoint button. To open the

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generator click on the Open Device button. Note that once a generator is opened you

cannot reclose it for the duration of the simulation.

To shed load right click on the gray load fields shown on the oneline, with each field

displaying the amount of load that will be shed. This displays the Load Information

dialog. Click the Open Device button to shed load. Note, you can also use the Close

Device button to reclose load that you had previously shed (which will help to minimize

the Unserved MWh metric). Try to save the system, with the metric being the total

unserved MWh of load.

4. Iterate through the scenario a number of times, trying to develop an optimal strategy.

Save a copy of the display at either the end of the simulation or at the time of blackout

with your best strategy for inclusion in your report.

Figure 7: Generator Dialog

Report:

For both the APL and TSGC systems, provide a summary of the procedures you followed and

the results you obtained.

For the DS scenarios, describe the strategy you used to solve the scenarios. What additional

information would have been helpful to have in developing your optimal strategy?