Power systems miscellaneous
- A 2-bus system and corresponding zero sequence network are shown in the figure.
The transformers T1 and T2 are connected as
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Correct Option: B
- Three-phase to ground fault takes place at locations F1 and F2 in the system shown in the figure
If the fault takes place at location F1, then the voltage and the current at bus A are VF1 and IF1 respectively. If the fault takes place at location F2, then the voltage and the current at bus A are VF2 and IF2 respectively. The correct statements about voltages and currents during faults at F1 and F2 is
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When fault takes place at F1
Current is feeding into the BUS A. It is like a generator delivering power to BUS (A) When fault takes place at F2, F2 point is like load, taking power from generator.Correct Option: C
When fault takes place at F1
Current is feeding into the BUS A. It is like a generator delivering power to BUS (A) When fault takes place at F2, F2 point is like load, taking power from generator.
- A 3-bus power system network consists of 3 transmission lines. The bus admittance matrix of the uncompensated system is
-j6 j3 j4 pu. j3 -j7 j5 -j4 j -j8
If the shunt capacitance of all transmission line is 50% compensated, the imaginary part of the 3rd row 3rd column element (in pu) of the bus admittance matrix after compensation is
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yBus = y10 + y12 + y13 -y12 -y13 -y12 y20 + y21 + y23 -y23 -y13 - y23 y30 + y31 + y32
Now comparing with the given matrix, we get and
y31 = y13 = – j4
y32 = y23 = – j5
thus, y30 + y31 + y32
∴ y30 + (-j4) + (-j5) = -j8
∴ y30 = j1
Now, after compensating, y30 = j1/2
∴ y30 + y31 + y32 = j0.5 – j4 – j5 = – j8.5
∴ Option (b) is correct.Correct Option: B
yBus = y10 + y12 + y13 -y12 -y13 -y12 y20 + y21 + y23 -y23 -y13 - y23 y30 + y31 + y32
Now comparing with the given matrix, we get and
y31 = y13 = – j4
y32 = y23 = – j5
thus, y30 + y31 + y32
∴ y30 + (-j4) + (-j5) = -j8
∴ y30 = j1
Now, after compensating, y30 = j1/2
∴ y30 + y31 + y32 = j0.5 – j4 – j5 = – j8.5
∴ Option (b) is correct.
- A sustained t hr ee-phase fault occurs in the power system shown in the figure. The current and voltage phasors during the fault (on a common reference), after the natural transients have died down, are also shown. Where is the fault located?
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NA
Correct Option: B
NA
- Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. Assertion: Fast decoupled load flow method gives approximate load flow solution because it uses several assumptions.
Reason: Accuracy depends on the power mismatch vector tolerance.
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NA
Correct Option: D
NA