Shunt Susceptance of Capacitors

I'll respond by giving my understanding of the terms "Shunt" and "Susceptance". This might be enough to help. It is possible the terms have a specific meaning that I don't know of in some context. Maybe somone else will clarify that.

"the susceptance ... is the imaginary part of the admittance" to cut and paste straight out of Wikipedea.

"Shunt" is another way of saying "in parallel" or "wired across" as opposed to be added in "series"

You may have found that already and been left just as baffled.

Forgive me if I start from basics, but it may help.

In a simple dc circuit you apply a voltage to a resistance and a current flows. The beheviour of this is governed by "ohms" law V=IR where V is the voltage in volts, I is the current in amps and R is the resistance in Ohms.

If you are dealing with materials that conduct very well the "Ohm" values can become so small as to be difficult to deal with. In these cases is may be more convenient to use a variation of Ohms law where the resistance is replaced by "conductance" - this is simply 1/R or the reciprocal of Ohms. Years ago the unit of conductance was the "mho" (Ohms spelt backwards) but these days the unit is usually called "Seimens". If conductance is represented by "C" then Ohms law becomes I=VC.

When ac is involved and things like capacitance and inductance are involved the relationship between the voltage and current becomes more complicated. For a start the current and voltage do not rise and fall at the same time. If we ignore that for the moment then if there is just an applied voltage and an inductance then V=IX where X=2pfL where L is the inductance in Henries, f the frequency in Hertz, p is mathematical pi (sorry I couldn't find the way to display the greek symbol normally used). If only a capacitor is involved we still have V=IX but this time X=1/(2pfC) where C is the capacitance in Farads. This "X" contribution is called "Reactance" rather than resistance.

In the same way as "Conductance" is the reciprocal of "Resistance", "Susceptance" is the reciprocal of "Reactance" so S=1/X where S is the Susceptance.

Without going into a lot more detail I'll briefly go back to the "current and voltage do not rise and fall together" that I ignored a couple of paragraphs ago. If we have a circuit which involves both "normal" resistance as well as reactance then Ohms law becomes V=I(R+jX) (sometimes written V=I(R+iX). The j (or i) makes the calculation involve "complex" numbers which I am not going to try and explain here more than to say that the "j" part is called the "imaginary" part. Sufficient to say that the combination of resistance and reactance (the R+jX) is called "Impedance" and it also has a reciprocal which is called "Admittance". Hence the Wikipedia assertion that "Susceptance" is the imaginary part of "Admittance".

Is this any help? If not perhaps you could clarify the context in which you have come across the term "shunt susceptance"