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A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.
Correct answer is between '2.7,3.2'. Can you explain this answer?
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A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It ...
Given:
- Synchronous generator: 30 MVA, 13.2 kV
- Solid grounded neutral
- Positive sequence impedance: 0.30 PU
- Negative sequence impedance: 0.40 PU
- Zero sequence impedance: 0.05 PU
To find:
- Value of reactance in the neutral to restrict fault current to rated line current for a double line to ground fault
Solution:
1. Find the fault current:
The fault current for a double line to ground fault is given by the equation:
I_fault = (V_line / (sqrt(3) * Z_seq)
Where:
- I_fault is the fault current
- V_line is the line voltage
- Z_seq is the sequence impedance
For a double line to ground fault, the fault current is equal to the positive sequence current since the negative and zero sequence currents cancel each other out. Therefore, we can use the positive sequence impedance to calculate the fault current.
Given:
- Line voltage (V_line) = 13.2 kV
- Positive sequence impedance (Z_seq) = 0.30 PU
Substituting the values into the equation, we can calculate the fault current:
I_fault = (13.2 kV / (sqrt(3) * 0.30 PU)
2. Calculate the rated line current:
The rated line current for the generator can be calculated using the formula:
I_rated = S_rated / (sqrt(3) * V_line)
Where:
- I_rated is the rated line current
- S_rated is the rated apparent power of the generator
Given:
- Rated apparent power (S_rated) = 30 MVA
- Line voltage (V_line) = 13.2 kV
Substituting the values into the equation, we can calculate the rated line current:
I_rated = (30 MVA / (sqrt(3) * 13.2 kV)
3. Restricting the fault current:
To restrict the fault current to the rated line current, we need to add a reactance (X_neutral) in the neutral of the generator. The reactance value can be calculated using the formula:
X_neutral = (V_line / I_rated) - (V_line / I_fault)
Given:
- Line voltage (V_line) = 13.2 kV
- Rated line current (I_rated) = Calculated in step 2
- Fault current (I_fault) = Calculated in step 1
Substituting the values into the equation, we can calculate the reactance in the neutral of the generator:
X_neutral = (13.2 kV / I_rated) - (13.2 kV / I_fault)
The calculated value of X_neutral should be between 2.7 and 3.2 ohms to restrict the fault current to the rated line current for a double line to ground fault.
- Synchronous generator: 30 MVA, 13.2 kV
- Solid grounded neutral
- Positive sequence impedance: 0.30 PU
- Negative sequence impedance: 0.40 PU
- Zero sequence impedance: 0.05 PU
To find:
- Value of reactance in the neutral to restrict fault current to rated line current for a double line to ground fault
Solution:
1. Find the fault current:
The fault current for a double line to ground fault is given by the equation:
I_fault = (V_line / (sqrt(3) * Z_seq)
Where:
- I_fault is the fault current
- V_line is the line voltage
- Z_seq is the sequence impedance
For a double line to ground fault, the fault current is equal to the positive sequence current since the negative and zero sequence currents cancel each other out. Therefore, we can use the positive sequence impedance to calculate the fault current.
Given:
- Line voltage (V_line) = 13.2 kV
- Positive sequence impedance (Z_seq) = 0.30 PU
Substituting the values into the equation, we can calculate the fault current:
I_fault = (13.2 kV / (sqrt(3) * 0.30 PU)
2. Calculate the rated line current:
The rated line current for the generator can be calculated using the formula:
I_rated = S_rated / (sqrt(3) * V_line)
Where:
- I_rated is the rated line current
- S_rated is the rated apparent power of the generator
Given:
- Rated apparent power (S_rated) = 30 MVA
- Line voltage (V_line) = 13.2 kV
Substituting the values into the equation, we can calculate the rated line current:
I_rated = (30 MVA / (sqrt(3) * 13.2 kV)
3. Restricting the fault current:
To restrict the fault current to the rated line current, we need to add a reactance (X_neutral) in the neutral of the generator. The reactance value can be calculated using the formula:
X_neutral = (V_line / I_rated) - (V_line / I_fault)
Given:
- Line voltage (V_line) = 13.2 kV
- Rated line current (I_rated) = Calculated in step 2
- Fault current (I_fault) = Calculated in step 1
Substituting the values into the equation, we can calculate the reactance in the neutral of the generator:
X_neutral = (13.2 kV / I_rated) - (13.2 kV / I_fault)
The calculated value of X_neutral should be between 2.7 and 3.2 ohms to restrict the fault current to the rated line current for a double line to ground fault.
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Community Answer
A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It ...
First find rated current of generator
Taking rated voltage and MVA as base
Z1 = j0.30 PU, Z2 = J 0.40 PU Z0 = J 0
Double line to ground fault
∴ 0.12 + 0.7 (0.05 + 3Xn) = 1.2
Xn = 0.5 PU = 0.5 × 5.88 = 2.94 Ω
Taking rated voltage and MVA as base
Z1 = j0.30 PU, Z2 = J 0.40 PU Z0 = J 0
Double line to ground fault
∴ 0.12 + 0.7 (0.05 + 3Xn) = 1.2
Xn = 0.5 PU = 0.5 × 5.88 = 2.94 Ω
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A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. Can you explain this answer?
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A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. 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, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. 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, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. Can you explain this answer?.
A 30 MVA, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. 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, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. 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, 13.2 KV synchronous generator has solid grounded neural. It positive, negative and zero sequence impedance are 0.30, 0.40 and 0.05 PU respectively. What value of reactance (in ohm) must be placed in the neutral of the generator to restrict the fault current to ground to rated line current for a double line to ground fault.Correct answer is between '2.7,3.2'. Can you explain this answer?.
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