Explain why the positive sequence impedance of a transmission line and transformer is the same as...

Explain why the positive sequence impedance of a transmission line and transformer is the same as the negative sequence impedance but is different from the zero sequence impedance.

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Expert Solution

The impedance offered by the system to the flow of positive sequence current is called Positive sequence impedance

The impedance offered by the system to the flow of negative sequence current is called Negative sequence impedance

The impedance offered by the system to the flow of zero sequence current is known as Zero sequence impedance

The sequence impedance varies with the type of power system components under consideration :-

1) 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

2) But in case of rotating machines the positive and negative sequence impedance are different

3) The assignment of zero sequence impedance values is more complex one. This is because the three zero sequence current at any point in a electrical power system, being in phase, do not sum to zero but must return through the neutral and /or earth.In three phase transformer and machine fluxes due to zero sequence components do not sum to zero in the yolk.

Manojponduru answered 1 year ago

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