GATE EE 2025 Set 1 — Question 33
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Power Systems → Fault Analysis → Symmetrical Faults
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Question
The bus impedance matrix of a 3-bus system (in pu) is A symmetrical fault (through a fault impedance of pu) occurs at bus 2. Neglecting pre-fault loading conditions, the voltage at bus 1, during the fault is ________ pu (round off to three decimal places).
Correct answer
0.38 to 0.4
Solution
1.Identify the pre-fault conditions: Neglecting pre-fault loading, the pre-fault voltage at all buses is assumed to be pu.
2.Identify the fault parameters: A symmetrical fault occurs at bus 2 through a fault impedance pu.
3.Calculate the fault current ():
The fault current at bus 2 is given by:From the given matrix, the diagonal element for bus 2 is pu.
4.Calculate the voltage at bus 1 during the fault ():
The change in voltage at bus 1 due to the fault is . Thus, the voltage during the fault is:From the given matrix, the mutual impedance between bus 1 and bus 2 is pu.
5.Final Answer: Rounding to three decimal places as requested, the voltage at bus 1 is pu.
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