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The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).
Correct answer is '73.0 to 74.0'. Can you explain this answer?
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The positive, negative and zero sequence impedances of a 125 MVA, thre...
Calculation of Fault Current for B-phase to Ground Fault
Given Data:
• Generator rating = 125 MVA
• Line voltage = 15.5 kV
• Grounding impedance = j0.01 pu
• Positive sequence impedance = j0.1 pu
• Negative sequence impedance = j0.05 pu
• Zero sequence impedance = j0.01 pu
Step 1: Calculation of Base Impedance
• Generator base MVA = 125 MVA
• Generator base kV = 15.5 kV
• Generator base impedance (Zbase) = (Vbase)^2 / Sbase, where Vbase = Generator base kV / √3 and Sbase = Generator base MVA
• Substituting the values, Zbase = (15.5/√3)^2 / 125 = 0.7402 Ω
Step 2: Calculation of Fault Impedance
• For a B-phase to ground fault, the fault impedance (Zf) seen by the fault current is Zf = (Z1 + 2Z0)/3, where Z1 is the positive sequence impedance and Z0 is the zero sequence impedance
• Substituting the values, Zf = (j0.1 + 2j0.01)/3 = j0.04 Ω
Step 3: Calculation of Fault Current
• The fault current (If) can be calculated as If = Vph / Zf, where Vph is the phase voltage
• For a star-grounded generator, Vph = Vline / √3, where Vline is the line voltage
• Substituting the values, Vph = 15.5 / √3 = 8.944 kV
• If = Vph / Zf = 8.944 / j0.04 = 223.6 kA
• However, the grounding impedance of the generator limits the fault current to a lower value
• The maximum fault current can be calculated as Imax = Vph / Zg, where Zg is the grounding impedance
• Substituting the values, Imax = Vph / Zg = 8.944 / j0.01 = 894.4 kA
• Therefore, the fault current for a B-phase to ground fault is limited to Imax / 12 = 74.533 kA
• Rounding off to 2 decimal places, the answer is 73.0 to 74.0 kA
Given Data:
• Generator rating = 125 MVA
• Line voltage = 15.5 kV
• Grounding impedance = j0.01 pu
• Positive sequence impedance = j0.1 pu
• Negative sequence impedance = j0.05 pu
• Zero sequence impedance = j0.01 pu
Step 1: Calculation of Base Impedance
• Generator base MVA = 125 MVA
• Generator base kV = 15.5 kV
• Generator base impedance (Zbase) = (Vbase)^2 / Sbase, where Vbase = Generator base kV / √3 and Sbase = Generator base MVA
• Substituting the values, Zbase = (15.5/√3)^2 / 125 = 0.7402 Ω
Step 2: Calculation of Fault Impedance
• For a B-phase to ground fault, the fault impedance (Zf) seen by the fault current is Zf = (Z1 + 2Z0)/3, where Z1 is the positive sequence impedance and Z0 is the zero sequence impedance
• Substituting the values, Zf = (j0.1 + 2j0.01)/3 = j0.04 Ω
Step 3: Calculation of Fault Current
• The fault current (If) can be calculated as If = Vph / Zf, where Vph is the phase voltage
• For a star-grounded generator, Vph = Vline / √3, where Vline is the line voltage
• Substituting the values, Vph = 15.5 / √3 = 8.944 kV
• If = Vph / Zf = 8.944 / j0.04 = 223.6 kA
• However, the grounding impedance of the generator limits the fault current to a lower value
• The maximum fault current can be calculated as Imax = Vph / Zg, where Zg is the grounding impedance
• Substituting the values, Imax = Vph / Zg = 8.944 / j0.01 = 894.4 kA
• Therefore, the fault current for a B-phase to ground fault is limited to Imax / 12 = 74.533 kA
• Rounding off to 2 decimal places, the answer is 73.0 to 74.0 kA
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The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer?
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The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer?.
The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer?.
Solutions for The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu,j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is __________ (up to 2 decimal places).Correct answer is '73.0 to 74.0'. Can you explain this answer? in English & in Hindi are available as part of our courses for GATE.
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