ECE470 POWER SYSTEMS I Homework Set 9 1. a) The currents feeding a Y-connected unbalanced load are: IA = 50/36.9 A IB = 30/-90 A IC = 40/180 A i) Determine the sequence components, Ia1,Ia2, and Ia0. ii) Is the load grounded or ungrounded? b) The phase voltages of a wye-connected unbalanced load are: VAB = 250/0 V VBC = 150/-126.9 V VCA = 200/143.1 V i) Determine the sequence components, Van1,Van2, and Van0. ii) Determine the unbalanced phase voltages, Van,Vbn, and Vcn. c) The sequence components of currents feeding an unbalanced load are: Ia0 = 10/45 A Ia1 = 50/0 A Ia2 = 20/-60 A iii) Determine the phase currents, IA,IB, and IC. iv) What is the load configuration?2. Draw the positive, negative and zero sequence reactance diagrams, for the system shown below, using a 200 MVA, 230 kV base in the zone of line 2 - 3. 3. If all excitation voltages are 1 pu, determine the Thevenin Equivalents for the positive, negative and zero sequence networks, for faults at bus 3. 4. Calculate the phase voltages and phase currents at bus 3 for the following faults: i) 1φ-G ii) 3φ-G iii) 2φ iv)
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