Recent energy market deregulation, along with new potential energy supplier rising, had lead to many and different type of invoicing whichare not very clear in showing Power Factor up.
However as energy final price is steady growing, to correct power factor is becoming more and more convenient. In most of the cases power factor improvement device prime cost is paid back in few months.
Technical-economical advantages of the installation of a capacitor
bank are the following:
The current I, that flows in the system, is calculated by
P = Active Power,
V = Nominal Voltage.
While cosÏ• increases, with the same absorbed power we can obtain a reduction in the value of the current and as a consequence the losses in the network and on the transformers are reduced. Therefore we have an important saving on the size of electrical equipment used on a system. The best system sizing has some consequence on the line voltage drop. We can easily see that looking at the following formula:
P= active power on the network (kW)
Q= reactive power on the network (kvar)
while R is the wire resistance and X its reactance (R<<X). The capacitor bank installation reduces Q so we have a lower voltage drop. If, for a wrong calculation of the installed capacitor bank value, the reactive part of the above equation becomes negative, instead of a reduction of the voltage drop we have an increasing of the voltage at the end of the line (Ferranti Effect) with dangerous consequence for the installed loads.
Hereinafter some examples:
1) Copper wire 3x25mm2, length 100m, 40kW load at 400Vac
2) 100kVA transformer
As we can see as the power factor increases we have fewer losses in the network and more active power.
This allows us to optimise on the system sizing.