Figure 1 shows the schematic diagram of a three phase radial transmission system. The ratings and reactance of various components are as shown, along with the nominal transformer rated line voltage. Convert the schematic into an equivalent per unit circuit by using a base of 250 MVA and voltage reference as 40 kV at Zone C. Subsequently, calculate the new per unit reactance for all zones and load current at the receiving busbar.

Figure 1 shows the schematic diagram of a three phase radial transmission system. The ratings and reactance of various components are as shown, along with the nominal transformer rated line voltage. Convert the schematic into an equivalent per unit circuit by using a base of 250 MVA and voltage reference as 40 kV at Zone C. Subsequently, calculate the new per unit reactance for all zones and load current at the receiving busbar.

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter9: Unsymmetrical Faults

Section: Chapter Questions

Problem 9.1P

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Equipment ratings for the five-bus power system shown in Figure 7.15 are as follows: Generator G1:Â Â Â Â 50Â MVA,Â 12kV,Â X=0.2 per unit Generator G2: 100Â MVA, 15 kV, X=0.2 per unit Transformer T1: 50 MVA, 10 kV Y/138kVY,X=0.10 per unit Transformer T2: 100 MVA, 15 kV /138kVY,X=0.10 per unit Each 138-kV line: X1=40 A three-phase short circuit occurs at bus 5, where the prefault voltage is 15 kV. Prefault load current is neglected. (a) Draw the positive-sequence reactance diagram in unit on a 100-MVA, 15-kV base in the zone of generator G2. Determine (b) the ThĂ©venin equivalent at the fault, (c) the subtransient fault current in per unit and in kA rms, and (d) contributions to the fault from generator G2 and from transformer T2.
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