Capacitor banks and reactors

Capacitor banks and Reactors

We have already discussed the significance of reactive power in a power system, As we know the availability of reactive power depends on the excitation of the alternators.This reactive power can be provided by the generators themselves, through the adjustment of generator excitation, but it is often cheaper to provide it through capacitors, hence capacitors are often placed near inductive loads to inject reactive power.the so called capacitors are mainly of two, static condensers and synchronous condensers. The synchronous condensers have a variable value of VAR which can be varied by the excitation of the synchronous motor and the static capacitors have a fixed value of VAR.

                                      The capacitor bank simply means that a group of  individual capacitors connected in  parallel and series accordingly to the design of the capacitor bank and together have a value in KVAR or MVAR.

Capacitor Connection

 A reactor is connected in series with the capacitor banks, reactors consume reactive power and are used to regulate voltage on long transmission lines, the efficiency of the power system may actually be improved by switching in reactors. Reactors installed in series in a power system also limit rushes of current flow, small reactors are therefore almost always installed in series with capacitors to limit the current rush associated with switching in a capacitor.

Reactor in series with capacitors

The below is a typical star connected capacitor bank. In practical condition the capacitor bank of large VAR value always has series reactor, the inrush current will be incredibly large while switching the reactor limits that.

                   Diagram 

   

             
 Large capacitor bank

 Capacitor banks are placed at appropriate grid stations by conducting careful power flow analysis by power engineers, the voltage level and VAR rating is determined by considering all aspects of the system, The banks are operated by two methods viz voltage control and power factor method though they means same and it can be detailed later!!😅