# Homework Help: Line impedance

1. Oct 17, 2006

### kim82

Can anyone tell me what is the relationship between the actual line impedance with the zero sequence impedances and positive sequence impedance?

Let say I have the
zero sequence impedance=0.15+1.79j
positive sequence impedance=0.013+j*0.32

what is the actual impendance?
In real life, what impedance should can we get?

2. Dec 1, 2006

### Newton1Law

The "real" impedance is the vector sum of the positive, negative and zero sequence components. The positive sequence impeadance is a set of balanced CCW rotating phasers, the negative sequence impedance is a set of balanced CW rotating phasers, the zero sequence impedances are a set of balanced non-rotating phasers. The vector sum of which will give you the real system impedances. If the system is perfectly balanced, solving for the sequence components will give you only the positive sequence components with a zero value for the negative and zero sequence components.

Generally you use sequence component transforms to solve imbalanced three phase system problems. Hope this helps.