What is Positive Sequency?

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For the study of the unsymmetrical fault (such as single line to ground fault, double line to ground fault, line to line fault), the fault current and the system voltages at fault point are not balanced. For the simplification of the unsymmetrical fault calculation, the unbalanced phasors (current, voltage etc.) are resolved into balanced components called symmetrical components. A three phase unbalanced phasors are represented by three components such as

1. Positive sequence component - three equal phasors, each having 120 degree phase displacement and rotating in same phase sequence of the original phasor,

2. Negative sequence component - three equal phasors, each having 120 degree phase displacement and rotating in opposite phase sequence of the original phasor and

3. Zero sequence component - three equal phasors with zero phase displacement.

As already mentioned, the symmetrical components method is used for the solution fault current of the unsymmetrical faults in power system.

- MS