| 10.4 |
Modeling Network in Sequence Components |
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We now show that corresponding network modeling can also be simplified in sequence domain. If the three phase network elements enjoy a particular symmetry (circulant structure) then, application of sequence component transformation diagonalizes three phase impedance or admittance matrix. Thus, we achieve decoupling in positive, negative and zero sequence networks, provided that network is balanced. Hence, sequence component analysis is used when network is balanced but phasors or loads are unbalanced. To begin with, consider a transposed transmission line whose three phase model is given by the following equation. Zs is the self impedance of transmission line and Zm is the mutual impedance between two phases. These quantities can be evaluated from GMD and GMR of transmission line.
 ,  and
 is the drop in phase voltage across the line due to currents Ia, Ib and Ic respectively then, |
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(8) |
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Applying the transformation, |
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and |
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 with phase 'a' as reference phasor. |
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we get, |
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Where |
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Hence, |
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(9) |
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