Problem 3 (25%): A three phase distribution substation transformer is rated 24MVA, 8% impedance, 115,000/14,400 volts co

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Problem 3 25 A Three Phase Distribution Substation Transformer Is Rated 24mva 8 Impedance 115 000 14 400 Volts Co 1 (42 KiB) Viewed 36 times

Problem 3 (25%): A three phase distribution substation transformer is rated 24MVA, 8% impedance, 115,000/14,400 volts connected delta-wye grounded. This transformer has a 5 position no-load tap changer (NLTC) connected to its high-voltage side with each tap position (A,B,C,D,E) rated +/- 2.5% centered around the nominal 115,000 volts. a) What are the transformer's high-side voltage ratings for each of the 5 NLTC tap positions? b) If the historical high side system voltages feeding this transformer are known to vary between 115,436 and 119,593 volts, which is the best of the 5 NLTC settings to guarantee no greater than 14,300 volts on the low-side of the transformer under no-load conditions? c) Based on your tap selection chosen in part b) and assuming the transformer operates at rated full load at a low-side power factor of 0.8 lagging, determine the voltage drop across this transformer when the high-side voltage is 119,593 V. d) Under the assumptions used in parte), approximately how much transformer loading is acceptable to limit the transformer voltage drop to no greater than 5%?