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GATE 2020 || Power Systems || Quiz 7

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Question 1

Z_bus of a power system given as

and prefault voltages are 1.0 p.u. If a 3φ fault occurred at bus ‘2’, post fault voltages at bus ‘1’ and bus ‘3’ respectively______.

Question 2

When a fault occurs in a power system the following sequence currents are recorded.
I_Zero = –j1.246 pu ;
I_Positive = j 2.046 pu ;
I_Negative = –j 0.8 pu.
The fault is

Question 3

A 500 MVA, 50 Hz, 3-phase turbo-generator produces power at 22 kV. Generator is Y-connected and its neutral is solidly grounded. Their sequence reactances are X₁ = X₂ = 0.15 and X₀ = 0.05pu. it is operating at rated voltage and disconnected from the rest of the system (no load). The magnitude of the sub-transient line current for single line ground fault at the generator terminal in pu will be

Question 4

A 10 MVA, 13.8 kV alternator has positive, negative and zero sequence reactances of 30%, 40% and 5% respectively. The value of resistance that must be placed in the generator neutral so that the fault current for a line to ground fault of zero fault impedance will not exceed the rated line current is

Question 5

A three phase, 500 MVA, 21.1 kV generator has solidly grounded neutral. The Z₁, Z₂, Z₀ of the generator are 0.2 pu, 0.2 pu, and 0.05 pu, respectively, at the base quantities. If a LG fault occurs at the terminal of the unloaded generator, the fault current in amperes immediately after the fault (kA) is _________.

Question 6

A 25 MVA, 11 kV generator has

its negative and zero sequence reactances are respectively 0.3 and 0.1 pu. The neutral of generator is solidly grounded. If the fault occurred in line to line on b and c phases, then line to line voltage V_ab is.

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ESE & GATE EE Power Systems

Jan 22ESE & GATE EE