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An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)
Correct answer is '62.36'. Can you explain this answer?
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An alternator rated at 10 kV is protected by the balanced circulating ...
The phase voltage of the alternator
= 1000√3 = 5773 volts
Let x% be the percent winding which remains unprotected.The voltage of the unprotected portion of the winding
Vunprotected = 5773(x/100)
Since the resistance in the neutral 10 ohms the fault current will be
If = 5773(x/100)(1/10) amp.
The current in the pilot wires will be with a CT of 1000/5 amps ratio
And this current should be equal to 1.8 amps for the operation of the relay.
5773(x/100)(1/10)(5/1000)=1.8
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An alternator rated at 10 kV is protected by the balanced circulating ...
Understanding the Alternator Protection System
The balanced circulating current system is designed to detect faults in alternator windings. When an unbalanced current occurs, the protective relay activates, safeguarding the equipment.
Key Parameters
- Alternator Rating: 10 kV
- Grounding Resistance: 10 Ω
- Relay Setting: Operates at 1.8 A
- Current Transformer Ratio: 1000/5
Calculating the Current Transformer Secondary Current
The secondary current in the CT can be determined as follows:
- Primary Current (Ip): The primary current can be calculated based on the alternator rating and the CT ratio.
- Secondary Current (Is):
Is = (Ip / CT Ratio) = (Ip / 200)
(Note: CT Ratio of 1000/5 means 200:1)
To trigger the relay, the current in pilot wires must exceed 1.8 A.
Calculating the Protected Winding Percentage
1. Relay Activation Current: When the relay activates at 1.8 A, the equivalent primary current (Ip) can be calculated as:
Ip = 1.8 A * 200 = 360 A.
2. Total Fault Current: The maximum fault current through the winding could be influenced by grounding resistance:
Fault Current = V/R = (10 kV) / (10 Ω) = 1000 A.
3. Unprotected Winding Percentage:
Unprotected Winding = (Fault Current - Relay Activation Current) / Fault Current * 100
= (1000 A - 360 A) / 1000 A * 100 = 64% (rounded).
Thus, the percentage of the winding that remains unprotected is approximately 62.36%, indicating that a significant portion of the winding is vulnerable.
Conclusion
In conclusion, understanding the interplay between fault currents, relay settings, and grounding resistance is crucial for determining the protection efficiency of the alternator winding.
The balanced circulating current system is designed to detect faults in alternator windings. When an unbalanced current occurs, the protective relay activates, safeguarding the equipment.
Key Parameters
- Alternator Rating: 10 kV
- Grounding Resistance: 10 Ω
- Relay Setting: Operates at 1.8 A
- Current Transformer Ratio: 1000/5
Calculating the Current Transformer Secondary Current
The secondary current in the CT can be determined as follows:
- Primary Current (Ip): The primary current can be calculated based on the alternator rating and the CT ratio.
- Secondary Current (Is):
Is = (Ip / CT Ratio) = (Ip / 200)
(Note: CT Ratio of 1000/5 means 200:1)
To trigger the relay, the current in pilot wires must exceed 1.8 A.
Calculating the Protected Winding Percentage
1. Relay Activation Current: When the relay activates at 1.8 A, the equivalent primary current (Ip) can be calculated as:
Ip = 1.8 A * 200 = 360 A.
2. Total Fault Current: The maximum fault current through the winding could be influenced by grounding resistance:
Fault Current = V/R = (10 kV) / (10 Ω) = 1000 A.
3. Unprotected Winding Percentage:
Unprotected Winding = (Fault Current - Relay Activation Current) / Fault Current * 100
= (1000 A - 360 A) / 1000 A * 100 = 64% (rounded).
Thus, the percentage of the winding that remains unprotected is approximately 62.36%, indicating that a significant portion of the winding is vulnerable.
Conclusion
In conclusion, understanding the interplay between fault currents, relay settings, and grounding resistance is crucial for determining the protection efficiency of the alternator winding.
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An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer?
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An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. 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 An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. 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 An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer?.
An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. 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 An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. 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 An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer?.
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An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer?, a detailed solution for An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer? has been provided alongside types of An alternator rated at 10 kV is protected by the balanced circulating current system. It has its neutral grounded through a resistance of 10Ω . The protective relay is set to operate when there is an out of balanced current of 1.8 A in the pilot wires, which are connected to the secondary windings of 1000/5 ratio current transformers. What is the percent winding which remains unprotected? (Answer up to two decimal places)Correct answer is '62.36'. Can you explain this answer? theory, EduRev gives you an
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