symmetrical components

The positive sequence current of a transmission line is

• Always zero

• One third of negative sequence current

• Equal to negative sequence current

• three times the negative sequence current

When a fault occurs in a high-voltage transmission line, first the

• Circuit breaker operates then the relay

• Relay operates then the circuit breaker

• Relay operates, then successfully the isolator and the circuit breaker

• Isolator operates, then successfully the relay and the circuit breaker

Zero sequence impedance of the transmission line is

• equal to the positive sequence impedance of the line

• About 2.5 to 3 times the positive sequence impedance of the line

• Less than positive sequence impedance of the line

• none of the above

The positive sequence impedance of a feeder is 3 ohm. Its negative sequence impedance will be

• 3 ohm

• 4 ohm

• 1 ohm

• 2 ohm

In which type of fault, positive sequence and negative sequence voltages are equal

• Line to line fault

• Double line to ground fault

• Line to ground fault

• None of the above

Which of the network gets affected by the method of neutral grounding?

• Zero sequence network

• Positive sequence network

• Negative sequence network

• All of above

‘a’ is an operator used to symmetrical component analysis

• Which rotates the vector, it operates upon, through an angle 90° in the clockwise direction

• Which rotates the vector, it operates upon, through an angle 120°, in the counter-clockwise direction

• Which rotates the vector, it operates upon, through an angle120°, in the clockwise direction

• Which rotates the vector, it operates upon, through an angle 240°, in the clockwise direction

Which of the following statement is true?

• a = 0.5 – j 0.866

• a = 0.5 + j 0.866

• a⁴ = - a

• 1+a+a² = 0

What is the value of zero sequence impedance in line to line faults?

• Z₀ = 1

• Z₀ = ∞

• Z₀ = 3 Z_n

• Z₀ = 0

What percentage of fault occurring in the power system is line to line fault?

• 5 %

• 30 %

• 25 %

• 15 %