ELE4452_EF_A03_QS

ELE4452_EF_A03_QS - IGEE 402 Power System Analysis FINAL EXAMINATION SAMPLE Fall 2004 Special instructions Duration 180 minutes Material allowed a

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IGEE 402 – Power System Analysis FINAL EXAMINATION - SAMPLE Fall 2004 Special instructions: - Duration: 180 minutes. - Material allowed: a crib sheet (double sided 8.5 x 11), calculator. - Attempt 5 out of 7 questions. - Make any reasonable assumption. - All questions and sub-questions carry equal weight. QUESTION 1 (20 points) A single phase 550 V, 60 Hz feeder supplies 2 loads in parallel: (a) a 20 kW heating load; (b) a 50 kW motor load, with an efficiency of 0.90 and a power factor of 0.80 (lagging). (a) Draw the instantaneous current and voltage waveforms for the total load, indicating peak and rms values. Give the equation for the total instantaneous power and draw the waveform. Indicate the value of the total real power. (b) Draw the V-I vector diagram and the power diagram. Compute total reactive power and power factor. (b) A capacitor is connected in parallel with the loads to increase the power factor to 1.0. Compute the reactive power required from the capacitor. Redraw the power diagram. (c) Explain the benefits in having a unity power factor from (i) the utility point of view; (ii) the consumer point of view. QUESTION 2 (20 points) A single phase 24 kV/2.4 kV, 60 Hz transformer, with a series equivalent impedance of 0.2 + j 1.0 referred to the low-voltage side, is connected at the end of a transmission line of impedance 50 + j 400 . The transformer feeds a load drawing 200 kW, at a 0.8 power factor lagging, and 2300 V. (a) The feeder voltage is adjusted so that the load voltage is 2300 V. Assume the load voltage has an angle of 0 deg. Find the amplitude and angle of the voltage at the sending end of the transmission line. (Hint: refer all quantities to the low voltage side). (b) Compute the current in the transmission line, the losses in the transmission line and transformer, and the overall system efficiency. (c) Calculate the no-load voltage and the voltage regulation. (d) Explain how the voltage regulation can be reduced. (Hint: consider shunt compensation). QUESTION 3 (20 points) A three-phase feeder supplies three identical single-phase 135 kV/6.9 kV, 60 Hz, 100 MVA transformers, each with a leakage reactance of 0.15 pu on the transformer base, and connected in a
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IGEE 402 – Power System Analysis – FINAL EXAMINATION – SAMPLE Joós, G. Page 2 of 3 -Y connection. The load is a three-phase Y-connected 12 kV load, with per phase parameters of 60 MW, 0.85 power factor (lagging). A capacitor bank of three elements of impedance (- j 5 ) connected in is used for power factor correction. The secondary voltage is assumed to be 12 kV. (a) Compute the total power and total reactive power drawn from the feeder. (b) Draw the single line pu circuit, using a 300 MVA (three-phase), 12 kV base. (c) Compute the total line current, the total power and total reactive power drawn from the feeder, in pu. Compute the voltage at the feeder. Compare with results in (a).
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This note was uploaded on 09/16/2011 for the course ECSE 361 taught by Professor Franciscodgaliana during the Winter '09 term at McGill.

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ELE4452_EF_A03_QS - IGEE 402 Power System Analysis FINAL EXAMINATION SAMPLE Fall 2004 Special instructions Duration 180 minutes Material allowed a

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