# Shunt susceptance and line charging susceptance

1. Jul 11, 2012

### skyddar

Hi, anyone could explain what exact the "shunt susceptance" and "shunt conductance" are? and what's the difference between shunt susceptance and line charging susceptance?

In power system analysis, shunt susceptance and shunt conductance are bus elements. Whereas the line charging susceptance is an element of transmission line (pi-model) in formulation of Y-bus.
Shunt susceptance and line charging susceptance are also separated as different element for bus and branch indices respectively in most power analysis software such as matpower.
However, I've read some book such as "Modelling and Analysis of Electric Power Systems" by Göran Andersson which uses shunt susceptance Ysh to form the Y-bus matrix. thanks.

2. May 27, 2016

### Anonymous22

I'm aware this post is very old, but I am answering it because no one else has.

Shunt susceptance, and shunt conductance are components connected at buses, but are only theoretical models. They are used to model components such as a synchronous condensers, and transmission lines.

Line charging suspectance is a physical property of transmission lines, because there is a inherent capacitance in long distance lines.

In power systems analysis, we use the pi model intentionally to simplify the problem down to nodes and admittances between them. This allows us to use traditional circuit analysis to this, otherwise complex, problem.

This ties in with the text book you are reading. By converting the impedance, and line charging susceptance to admittances, we are able to form the Y-bus matrix to solve power systems problems.

The only reason I can think for software to separate shunt susceptance (such as a synchronous condenser) and line charging susceptance is for the sake of flexibility. It means the model and hence how your problem is solved can be changed without changing the input variables, i.e. if you decide the pi-model is not suitable for your analysis, you could just change it to a different model using settings in your software, without changing your input data.

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