Recent Question/Assignment

RMIT University, School of Engineering
Advanced Power Systems
Experiment 1 - Load Flow Analysis
? Objectives
? Familiarisation with the DIgSILENT Power Factory software package.
? Performing power flow analysis using a test power system.
? Analysing the relative sensitivities of active power and reactive power flows in lines to changes in voltage angles and magnitudes.
? Equipment and Software
DIgSILENT Power Factory Ver. 2019 which is available on all computers in the computer lab as well as RMIT myDesktop.
? Prerequisites
1. Revise relevant Lecture materials
2. Should complete DIgSILENT Power Factory Learning Tutorial available in Canvas
? DIgSILENT Power Factory Software Package
DIgSILENT Power Factory is the leading high-end power system analysis tool for applications in generation, transmission, distribution and industrial systems. It is integrating all required functions, easy to use, fully Windows compatible and combines reliable and flexible system modelling capabilities with state-of-the-art algorithms and a unique database concept. Besides the stand-alone functionality, the Power Factory engine integrates smoothly into any GIS, DMS or EMS supporting open system standards. The DIgSILENT offers following functionalities.
? Balanced and unbalanced power flow;
? Fault analysis;
? Harmonics, Frequency scans;
? RMS Stability;
? EMT simulations for three, two and single phase AC systems and DC systems;
? Protection simulation and co-ordination;
? Distribution, transmission and generation reliability;
? Small signal analysis (eigenvalues);
? Static and dynamic voltage stability;
? Active and reactive power dispatch;
? State estimation;
? Open tie optimization, optimal capacitor placement, cable sizing;
? Built-in automation interface (DPL),
? ODBC driver, interfaces for GIS and SCADA integration; PSS/E compatibility
? Experimental Procedure:
? 1) Download “Experiment-1.pfd” and save it in your computer. Open the DIgSILENT Power Factory (PF) and then go to: “File Import Data (*.pfd,*.dz,*.dle)”. Then select the
“Experiment-1.pfd” file from the place where you saved it in the computer and then click “Open”. Then activate the project: “File Activate Project” and select the project “Experiment-1” and press “OK”. A schematic of the network model is shown in Figure 1.
2) Once you activated the “Experiment-1.pfd”, modify the model using the following data and run the load flow simulation and determine the magnitudes and angles of all the bus voltages as well as the branch active and reactive power flows. Tabulate the results in a Table.
Bus Data(7busses) Base MVA = 100 MVA Base V= 110 kV
Name Type Vmag pu P load MW Q load MVAR P Gen MW Q Gen
Bus1 Slack 1.06 0 0 ? ?
Bus2 P-V 1.045 21.2 12.8 38 ?
Bus3QC P-V 1.01 94.5 19.3 0 ?
Bus4 P-Q ? 47.9 -3.8 0 0
Bus5 P-Q ? 7.7 1.9 0 0
Bus6 P-Q ? 43.8 24 0 0
Bus7QC P-V 1.068 43.8 20.6 0 ?
Branch Data (9 Branches)
Branch Start End Resistance-R (pu) Reactance-X Susceptance-B Tap (HV Side)
Line1 1 2 0.02 0.062 0.0528 0
Line2 1 5 0.053 0.219 0.0492 0
Line3 2 3 0.046 0.194 0.0438 0
Line4 2 5 0.059 0.179 0.0340 0
Line5 3 4 0.058 0.177 0.0346 0
Line6 3 5 0.066 0.168 0.0128 0
Line7 4 5 0.012 0.039 0 0
Transformer-1 4 7 0.02 0.279 0 0.975
Transformer-2 5 6 0.02 0.253 0 0.938

1. Transmission Line Parameters are given in pu and you may need to convert them into appropriate quantities before using them in the model. Line “Susceptance (B)” is specified in the “Load Flow” page of Line Type as “µS” hence you should convert the given pu values in table to “µS”. Similar approach must be followed for specifying the “AC-Resistance” and “Reactance”
(See Learning Tutorial for more information). Use 110 kV and 100 MVA as the base value for “pu” to “?” and “µS” conversion.
2. The specified bus voltage magnitudes in pu must be specified for the generators connected at the specified bus. Therefore, you should set the “Local Controller” to “Const. V” in “Load Flow” page in the synchronous generator. Then, specify the “pu” voltage in the “Dispatch” field.
3. Change the transformer tap voltage steps to 0.625% so the voltage range between 0.9 to 1 pu is covered through the tap-changer steps (round up the 3rd decimal point i.e. 0.9375=0.938).
3) Variation of Q at Bus#7
Keeping all other variables constant, change the reactive power Q of load on bus #7. Starting from zero, increase the value of Q in steps of 5 MVAR till you reach a value of 30 MVAR. At each step note the magnitude and angle on bus #7. Obtain the total active power loss in the system.
Draw a graph of bus #7 voltage magnitude and angle versus the Q MVAR of Load at bus#7. Also plot the total active power loss in the system versus the Q MVAR of “the load at bus#7. Choose appropriate scales for the graphs.
4) Variation of P at Bus#7
Now, set the Q value of the Load at bus#7 to the original value given in your data table. Change the active power P of the load at bus#7, from zero in steps of 5 MW till a value of 30 MW is reached. At each step note the magnitude and angle of bus#7 voltage. Note also the total active power loss in the system.
Draw a graph of bus #7 voltage magnitude and angle versus the P at bus#7. Also plot the total active power loss in the system versus the P MW of the load at bus#7.
Compare the changes in the magnitude (V) and angle (d) in both tasks (2) and (3). Comment on the sensitivity of V and d to changes in active and reactive powers of the load. Give theoretical explanations for your observations.
What can you observe in the variation of total active power losses? Give the reasons for the difference in the way power losses differ in both tasks.
5) Variation of Q at Bus#6
Now, set the P and Q values of Load at bus#7 to the original values given in your data table. Change the reactive power Q of load on bus #6. Starting from zero, increase the value of Q in steps of 5 MVAR till a final value of 30 MVAR is reached. At each step note the total active power loss in the system.
6) Variation of P at Bus#6
Restore the Q at bus#6 to the base case value. Change the active power P of the load at bus#6 in the same way (from 0 MW to 30 MW) and note the total power losses at each step.
Plot the total active power loss in the system versus the Q MVAR and P MW at bus#6. Comment on the differences in the two graphs.
7) Bus#3 Compensator switched OFF
Now, set the P and Q values of Load at bus#6 to the original values given in your data table. Switch off the compensator at bus#3. Note the bus#6 voltage magnitude and the total active power losses. Comment on your results and give reasons for the observed variations.
How to submit your Lab-Report?
The experiment should be performed either in a group of two or individually and the Lab report should be prepared accordingly. The lab report is due One Week after the scheduled Lab Session and should be submitted through Canvas. The experiment and report should include the following:
(i) Screen shot of the DIgSILENT Power Factory single-line diagram with the results for the simulated case including graphs and discussion for tasks 2 to 7. (MS Word or PDF)
(ii) Your DIgSILENT Power Factory *.pfd file should also be submitted with the report.

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