Reactive Power

Reactive Power

Reactive power is used to control voltage over transmission line or in power systems network.

Mathematically, Reactive Power is product of volage and current with sin(phi).

       Q = VI sin(phi) -----------(1)

Here, we observed that from eq.(1), Reactive Power depends upon flux (phi).

And We have,

  V = E1 = 4.44 Nf(phi) ----------(2)

    Where, phi = magnetic flux(Weber)

                    N  = No. of turns

                    f   = freuency(Hz)

From eqn(2),

We can says that, voltage depend upon flux.

By this way we can say that, Reactive Power depends upon voltage.

In case of synchronous machine:

Over excitation ---> Over flux ---> Over R.P

Need of Reactive Power :

Voltage control in power system is important for proper operation for electrical devices/elements to prevent from damage such as : 

-To reduces Transmission lines losses

-To mantain the ability of system and prevent Voltage collapse.

-Over heating of Electrical machine

- Reactive Power (VARs) is used to mantain the voltage to deliver Active/Useful power(W) through transmission lines.

- More Load requires reactive power to convert the flow of electron into useful work.

- When there is not reactive Power, the volatge sag down and it is not possible to push the power demanded by load through the lines.

--In case of inductive circuit,Reactive power is used to produce flux.

--In case of capacitive circuit, Reactive power is used to produce electric field.

Basic concept of inductor and Capacitor:

Inductor absorbs lagging Reactive power and deliver Leading Reactive power.

Capacitor absorbs Leading Reactive power and deliver Lagging Reactive power.