Chapter 9: Q9-3MCQ (page 576)
When calculating symmetrical three-phase fault currents, only ________ sequence network needs to be considered.
Answer
When calculating symmetrical three-phase fault currents, only positive sequence network needs to be considered.
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For a bolted three-phase-to-ground fault, sequence-fault currents ________ are zero, sequence fault voltages are ______, and line-to-ground voltages are ________.
For the five-bus network shown in Figure 9.25, a bolted single-line-toground fault occurs at the bus end of the transmission line between buses and. role="math" localid="1656410079694" The fault causes the circuit breaker at the bus end of the line to open, but all other breakers remain closed. The fault is shown in Figure 9.26. Compute the subtransient fault current with the circuit breaker at the bus- end of the faulted line open. Neglect prefault current and assume a prefault voltage ofrole="math" localid="1656410247948" per unit.
Faults at bus n in Problem 9.8 are of interest (the instructor selects , or ). Determine the Thevenin equivalent of each sequence network as viewed from the fault bus. Prefault voltage is 1.0 per unit. Prefault load currents and D–Y phase shifts are neglected.
At the general three-phase bus shown in Figure 9.7(a) of the text, consider a simultaneous single line-to-ground fault on phase a and line-to-line fault between phases and , with no fault impedances. Obtain the sequence-network interconnection satisfying the current and voltage constraints.
For a bolted three-phase-to-ground fault, sequence-fault currents ________ are zero, sequence fault voltages are ______, and line-to-ground voltages are ________.
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