Comparing Actual Line Impedance to Zero/Positive Sequence Impedance

[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?

 

[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.

 

[piercas]

The actual line impedance can be thought of as the total impedance of the line, taking into account the effects of both zero and positive sequence impedances. In other words, it is the combined impedance that is experienced by the line in real life conditions.

The relationship between the actual line impedance and the zero and positive sequence impedances can be described using the concept of sequence networks. These networks are used to represent the electrical properties of a power system, and they are based on the different types of currents that flow through the system.

In a balanced three-phase system, the zero sequence impedance represents the flow of currents that are in phase with each other, while the positive sequence impedance represents the flow of currents that are 120 degrees out of phase with each other. The actual line impedance takes into account the combination of these two types of currents, as well as any other factors that may affect the impedance of the line, such as line length, material, and temperature.

In the given example, the actual line impedance cannot be determined without knowing the specific conditions of the line. However, it can be said that the actual impedance will likely fall somewhere between the zero sequence and positive sequence impedances, as it is a combination of the two.

In real life, the actual impedance of a line can vary depending on a multitude of factors. It can be affected by the type of conductor used, the presence of any parallel paths, the type of load being supplied, and even weather conditions. Therefore, it is important to carefully calculate and measure the actual line impedance in order to ensure the proper functioning of the power system.