CapactiorBanks

[Engcan]

Hi everybody,
you guys have helped me earlier getting rid of some confusions and here once again to have a word from you.

First I will mention, what a capacitor bank comprises of and please correct me if I am wrong and then my question will follow.

Capacitor banks are connected in parallel and depending upon the manufacturer the banks internally may be connected in star or delta, which I beleive is not the users concern(Please correct, if I am wrong.

A capacitor acts as a shortcircuit on transient basis as it is hooked to supply and to avoid that transient inrush we use reactors.

The second point is when we are using capacitor banks in a industry we also use them for diverting harmonics into them so that they may not get in to supply where a lot of load is harmonics oriented like VFD etc. and then ofcourse banks are cooled by fans.

Now after you find what I wrote is correct, here is my question:

What is the difference between these surge reactors used for transient inrush current and detuning reactor which is used for haronics diversion ?
will it be pertinet to say that both type of capacitor banks are different and both cannot have both types of reactors in one and last these are always reactors not resistors.

I am sure you might have to put a bit of your time but would appreciate your time spent.
Regards,

 

[Engcan]

plz some expert would spare a moment for my question.. would appreciate it.

 

[LionelHutz]

The difference is the reactance of the reactor. A reactor to limit the inrush could be just 6 to 10 turns of wire coiled in air. A reactor to de-tune the capacitor bank typically uses an iron air gapped core and has more than 6 turns.

A detuning reactor will also limit inrush. A inrush reactor will usually not de-tune.

Sometimes, the star or delta internal connection is important when calculating the current that will be seen when a capacitor section (or roll) fails. Internally, a capacitor for high voltage is typically a number of rolled capacitors connected in series for each phase. So, having one series section fail in a delta configuration vs a star configuration can mean different fault or imbalance currents.

 

[unclebob]

Engcan,

Continuing with the use of capacitors in power systems,
it is also possible to connect them in series with transmission lines (series compensation) to reduce the reactance (imaginary part of impedence). Doing so, you increase the line loadability. This technique is used here
in Quebec with 735 kV lines.

 

[unclebob]

To add to my previous post, somebody here told me another advantage of series compensation.

During solar storms, ionized particules bombard the magnetic field of Earth causing magnetic storms,i.e,
fluctuations of the magnetic field. Very low frequency currents are induce and may travel in the long transmission lines, causing lots of problems. The capacitors stop these "near DC currents", increasing the stability of the line.

 

[LionelHutz]

unclebob, I believe there was a large scale blackout through Quebec (and parts of North-East USA??) some time ago caused by that effect.