The objective of this practical/simulation.

Objective The objective of this practical/simulation is to evaluate power flow solution of a general power system. The effects of generator specified voltage on its reactive power, load MVA on load voltage, and shunt compensation on voltage profile are also investigated. System Description The single line diagram of a 3-machine, 9-bus system is shown in Fig. 1. The transmission line/transformer data of the system on a 100 MVA base are also shown on the diagram. The tap setting of all transformers is considered as unity. The generator data and load data of the system is given in the following Tables. Generator data Bus Voltage magnitude, Generation, Reactive power limits, MVAr No pu MW Minimum Maximum 1 1.040* —– —- —– 2 1.025 163 -80 150 3 1.025 85 -75 100 * Swing bus Load data Load Active power, MW Reactive power, MVAr A 125 50 B 90 30 C 100 35 Procedure: 1. Prepare the “busdata” and “linedata” for power flow analysis. Typical format of “busdata” and “linedata” is given on page 3. 2. Construct the power flow admittance matrix using “lfybus” routine and obtain the power flow solution by the Newton Raphson method using “lfnewton” routine. Use basemva = 100, accuracy = 0.001 and maxiter = 20. You may display the bus results using “busout” routine and the line power flows results using “lineflow” routine. 3. Plot the voltage profile of the system (bar plot of voltage magnitude against bus number). 4. Change the specified voltage magnitude of generator bus 2 from 0.8 pu to 1.2 pu in step of 0.05 pu and obtain the power flow solution. Record the corresponding reactive power generated by the generator at bus 2. Plot the generated reactive power against specified voltage magnitude of bus 2. 5. Reset the voltage magnitude of bus 2 to the original value of 1.025 pu. Vary the load of bus 5 (from 50 MVA to 350 MVA in step of 25 MVA) at a constant power factor of 0.8 lagging. Obtain the power flow solution and record the corresponding voltage magnitude of bus 5. Plot the voltage magnitude against the load MVA of the bus. 6. Reset the load of bus 5 to the original value of (125+j50) MVA. Add a shunt reactive compensation at bus 5. Vary the injected reactive of the compensation (from -100 MVA to +150 MVA in step of 50 MVA) and obtain the power flow solution. Record the corresponding voltage magnitude of bus 5. Plot the voltage magnitude against injected reactive power. Discuss the effects of shunt compensation on bus voltage magnitude with suitable equivalent circuit and/or phasor diagram. Report: Results of steps 3 to 6 with critical analysis and discussions. Using the Ï€-circuit model and voltage at both ends of the transmission line connected between buses 5 and 7, calculate the complex power flow through the line at both ends. Compare the calculated values with the corresponding simulation results obtained in step 2 and find the error in percentage. What is the losses in the line? P-V and Q-V curves are commonly used as tools to assess static voltage stability limit of a power system. Discuss how the results of steps 4-5 be used to assess the static voltage stability limit of the system. Consider the Thevenin equivalent impedance of bus 5 is Zth = (0.02255+ j0.09285) pu at base load. Draw the Thevenin equivalent circuit using the results of step 2 (Note Vth = voltage of bus 5 at base load). Calculate the voltage magnitude of bus 5 when a 100 MVA shunt capacitor is connected to the bus. Compare the result with that found in step 6 and calculate the error in percentage. (First you may need to find the capacitor reactance as XC = V2/Qinj). Fig. 1 Single line diagram (including data) of the 3-machine, 9-bus system Typical format of “busdata” and “linedata” (for a different system) Bus code: 1 → swing (or V-δ) bus; 2 → voltage control (or P-V) bus, and 0 → load (or P-Q) bus Some Variables (power flow results): Vm : Bus voltage magnitude Pg: Generated real power, MW Pd: Load real power, MW Qsh: Shunt reactive power, MVAr deltad: angle in degree Qg: generated reactive power, MVAr Qd: load reactive power, MVAr

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