By installing a capacitor bank it is possible to reduce the reactive power absorbed by the inductive loads in the system and consequently the power factor improves.
It is suitable to have cosϕ a little in excess of 0.9 to avoid paying the penalties provided for by the law. cosϕ must not be too close to unity, to avoid the capacitive working of the electrical system.
The choice of the correct power factor correction equipment depends on the type of loads present and by their way of working.
The choice is between CENTRAL COMPENSATION and INDIVIDUAL COMPENSATION.
Individual compensation: power factor correction is sited at each single load (i.e. motor terminals).
Central compensation: we install only one bank of capacitors to a main power distribution station or substation.
The individual compensation is a simple technical solution: the capacitor and the user equipment follow the same sorts during the daily work, so the regulation of the cosj becomes systematic and closely linked to the load.
Another great advantage of this type of power factor correction is the simple installation with low costs.
The daily trend of the loads has a fundamental importance for the choice of power factor correction most suitable.
In lots of systems, not all the users work in the same time and some of them work only a few hours per day.
It is clear that the solution of the individual compensation becomes too expensive for the high number of capacitors that have to be installed. Most of these capacitors will not be used for long period of time. The individual compensation is most effective if the majority of the reactive power is concentrated on a few loads that contribute the greatest power and that work long period of time.
Central compensation is best suited for systems where the load fluctuates throughout the day.
If the absorption of reactive power is very variable, it is advisable the use of automatic regulation in preference to fixed capacitors.