What is the relationship between positive and negative sequence impedance of line?

In static and balanced power system components like transformer and lines, the sequence impedance offered by the system are the same for positive and negative sequence currents. In other words, the positive sequence impedance and negative sequence impedance are same for transformers and power lines.

What is the importance of sequence impedance?

The sequence impedance of the circuit tells about the behavior of the system during any type of asymmetrical fault condition i.e line to line fault or line to ground fault or line to line to line to ground (L-L-L-G) fault.

What is the significance of positive sequence component?

The positive sequence component of current or voltage has the same rotation as the power system. This component represents balanced load. If the generator phase currents are equal and displaced by exactly 120°, only positive-sequence current will exist.

What is the difference between positive negative and zero sequence?

The positive sequence component of current or voltage has the same rotation as the power system. This component represents balanced load. The negative sequence component has a rotation opposite that of the power system. The zero-sequence component represents an unbalance that causes current flow in the neutral.

What is negative sequence protection?

Definition: A relay which protects the electrical system from negative sequence component is called a negative sequence relay or unbalance phase relay. The negative sequence relay protects the generator and motor from the unbalanced load which mainly occurs because of the phase-to-phase faults.

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

In double line to ground fault, all the sequence networks are connected in parallel. Therefore, all the sequence voltages at the fault point are equal.

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