Capacitor Bank Placement

[Besoeker]

My losses are automatically calculated with our distribution analysis program.
But i would like to see how it is done.

I agree with that. Using software for this, or any electrical calculation for that matter, doesn't help much with understanding the fundamentals and you are also dependent on the approach taken by others.

I have one last question, a hypotetical one.
I know the capacitor supplies vars or reactive current to specific load or loads
lets say 10 Amps at lagging p.f .95 Now at .95 leading p.f. does it still provide the same 10 Amps to the same loads? Which of course would add to losses in the later case? And because of this extra current in the system, ( the current provided by the capacitor ) is this the reason why we get a voltage rise?

Maybe the simplified vector diagram I posted will help visualise the mechanism that produces voltage rise.

There is another important factor that you may need to take into account when rating the capacitors. That is loads that take harmonic currents. Anything that does will, to some extent, impose harmonic voltages on the supply.
In an industrial environment, variable speed drives are a common culprit - typically 5th, 7th, 11th, 13th etc. (6n ? 1). If they are on the same feed, the effect is generally cumulative.
The harmonic voltages, being higher frequency than the fundamental, result in higher total rms current in the capacitors. In a number of installations I have seen this cause overheating of the capacitors, reduced life, fuse failure etc.
I don't know what you have connected to your supply, but I think it may be something you need to consider, then possibly disregard.

 

[mull982]

Maybe the simplified vector diagram I posted will help visualise the mechanism that produces voltage rise.

.

Can you please give a really quick explanation of the vector diagrams you posted. I'm not seeing the complete picture or why the vecors are drawn the way they are to produce the Vz and i'm hoping with a quick explanation I'll see it.

Thanks

 

[Besoeker]

Can you please give a really quick explanation of the vector diagrams you posted. I'm not seeing the complete picture or why the vecors are drawn the way they are to produce the Vz and i'm hoping with a quick explanation I'll see it.
Thanks

I'll try.
Supply impedance (Vz) is mostly inductive thus the voltage leads the current. For simplicity I showed it as just inductive.

For a lagging load, the voltage leads the current. That's what's shown on the first vector diagram.

For a leading load, the voltage lags the current. That's what's shown on the second vector diagram.

 

[mull982]

I'll try.
Supply impedance (Vz) is mostly inductive thus the voltage leads the current. For simplicity I showed it as just inductive.

For a lagging load, the voltage leads the current. That's what's shown on the first vector diagram.

For a leading load, the voltage lags the current. That's what's shown on the second vector diagram.

I understand how the Is (current) and Voltage Source vectors are represented. (Supply voltage vector is leading or lagging Is vector depending on power factor). I am a little confused how the load voltage vector is represented? Does this vector start from the origin with the vector shifted at some angle depending on load pf and then vector is shifted vertically up or down do create vz depending on pf?

In other words I believe the load voltage is a vector that starts at the origin of the graph but is shifted vectically in this representation to show Vz.