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A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.
Correct answer is '4.549'. Can you explain this answer?
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A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly ...
Given : X1 = 2.5 Ω
[For current division rule]
X0 = 0.3X1 = 0.3 x 2.5 = 0.75 Ω
X2 = 0.8X1 = 0.7 x 2.5 = 2 Ω
Positive sequence current,
Zero sequence current,
[For current division rule]Current through ground is given by,
Hence, the current through ground is 4.549 kA.
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A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly ...
The given problem involves calculating the current through ground for a line-to-line-to-ground (LLG) fault in a 30 MVA, 3-phase, 11 kV, 50 Hz alternator with a solidly grounded neutral. Here is a detailed explanation of the solution:
Given data:
- Alternator rating: 30 MVA
- Voltage rating: 11 kV
- Frequency: 50 Hz
- Reactance to positive sequence currents (X1): 2.5 ohms
- Reactance to negative sequence currents (X2): 80% of X1 = 0.8 * 2.5 = 2 ohms
- Reactance to zero sequence currents (X0): 30% of X1 = 0.3 * 2.5 = 0.75 ohms
To find the current through ground during an LLG fault, we need to consider the faulted conditions. During an LLG fault, the fault impedance is zero for the faulted phase, and the other two phases are shorted to ground.
Steps to calculate the current through ground (IIg):
1. Find the fault current (If) using the formula:
If = (Line voltage) / (Impedance)
For an LLG fault, the impedance is the sum of positive, negative, and zero sequence impedances.
Impedance = X1 + X2 + X0
2. Find the fault current (If) using the formula:
If = (Line voltage) / (Impedance)
3. The current through ground (IIg) is the current flowing through the neutral point during the fault condition. It can be calculated using the formula:
IIg = (2 * If) / √3
Substituting the given values into the formulas:
Impedance = 2.5 + 2 + 0.75 = 5.25 ohms
If = (11 kV) / (5.25 ohms) = 2.0952 kA
IIg = (2 * 2.0952 kA) / √3
IIg = 4.549 kA (approx.)
Therefore, the current through ground during an LLG fault in this alternator is approximately 4.549 kA.
Given data:
- Alternator rating: 30 MVA
- Voltage rating: 11 kV
- Frequency: 50 Hz
- Reactance to positive sequence currents (X1): 2.5 ohms
- Reactance to negative sequence currents (X2): 80% of X1 = 0.8 * 2.5 = 2 ohms
- Reactance to zero sequence currents (X0): 30% of X1 = 0.3 * 2.5 = 0.75 ohms
To find the current through ground during an LLG fault, we need to consider the faulted conditions. During an LLG fault, the fault impedance is zero for the faulted phase, and the other two phases are shorted to ground.
Steps to calculate the current through ground (IIg):
1. Find the fault current (If) using the formula:
If = (Line voltage) / (Impedance)
For an LLG fault, the impedance is the sum of positive, negative, and zero sequence impedances.
Impedance = X1 + X2 + X0
2. Find the fault current (If) using the formula:
If = (Line voltage) / (Impedance)
3. The current through ground (IIg) is the current flowing through the neutral point during the fault condition. It can be calculated using the formula:
IIg = (2 * If) / √3
Substituting the given values into the formulas:
Impedance = 2.5 + 2 + 0.75 = 5.25 ohms
If = (11 kV) / (5.25 ohms) = 2.0952 kA
IIg = (2 * 2.0952 kA) / √3
IIg = 4.549 kA (approx.)
Therefore, the current through ground during an LLG fault in this alternator is approximately 4.549 kA.
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A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer?
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A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer?.
A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A 30 MVA, 3 phase 11 kV, 50 Hz alternator having the neutral solidly grounded is operating at no load. It has a reactance to positive sequence currents of 2.5 ohms, the reactance to negative and zero sequence current are 80% and 30 % of the positive sequence value respectively, then the current through ground is _____ kA for LLG fault.Correct answer is '4.549'. Can you explain this answer?.
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