The sequence reactance of an equipment is as follows : X 1 = X 2

The sequence reactance of an equipment is as follows : X 1 = X 2
| The sequence reactance of an equipment is as follows : X1 = X2 and X0 = 3.X1 

The element is

A. Synchronous machine

B. <p>Transformer</p>

C. Transmission line

D. Induction Motor

Please scroll down to see the correct answer and solution guide.

Right Answer is: C

SOLUTION

Sequence Impedance:

The sequence impedance of the network describes the behavior of the system under asymmetrical fault conditions.

Positive Sequence Impedance

  • The impedance offered by the network to the flow of positive sequence current is called the positive sequence impedance.
  • The positive sequence means all the electrical quantities are numerically equal and displaces each other by 120º.

Negative Sequence Impedance

The negative sequence impedance means the impedance offered by the network to the flows of negative sequence current.

Zero Sequence Impedance

The impedance offered to zero sequence current is called the zero sequence impedance.

Generally, resistance offered by the power system is less when compared to reactance.

So, the resistance of the system is neglected and reactance is considered.

Values of sequence reactance of some equipment are as follows:

 

Positive sequence impedance (X1)

Negative sequence impedance (X2)

Zero sequence impedance (X0)

Transmission line

X1

X2 = X1

X0 = 3 X1

Transformer

X1

X2 = X1

X0 = X1

Cylindrical rotor synchronous machine

Xd”

X2 = Xd”

X0 < < Xd”

Salient pole rotor Synchronous machine  

Xd”

X2 < Xd”

X0 < < Xd”

 

Where,

X0 is the zero sequence reactance

X1 is the positive sequence reactance

X2 is the negative sequence reactance

Xd” is the direct axis reactance

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