What is Reactive Power ?
Reactive power(Q) is the amount of power consumed or supplied by the reactive components, i.e. capacitors and inductors.
- While active power is the energy supplied to run a motor, heat a home, or illuminate an electric light bulb, reactive power provides the important function of regulating voltage. If voltage on the system is not high enough, active power cannot be supplied.
- Reactive power is used to provide the voltage levels necessary for active power to do useful work. Q is essential to move active power through the transmission and distribution system to the customer.
It can be expressed as
- (Reactive power)Q = S sin ϕ
Q = VI sin ϕ also calculated as =P tan ϕ
Where, S = apparent power and P = active power.
- Reactive power is temporarily stored in the form of electric or magnetic fields that flows back and forth due to capacitive and inductive components.
- Q can be generated as well as absorbed by power transmission system elements by virtue of shunt susceptance and series reactance respectively.
- It has its origin in phase shift, if current through a device lags the voltage, then the device consumes reactive power.
- Depending on the phase shift between the voltage and current, the amount of Q consumption of the device is decided.
Reactive Power Limitations
- It does not travel very far.
- Usually necessary to produce it close to the location where it is needed
- A source close to the location of the need is in a much better position to provide reactive power versus one that is located far from the location of the need
- It supplies are closely tied to the ability to deliver real or active power.
Need of reactive power
- Reactive power (VARs) is required to maintain the voltage to deliver active power (watts) through transmission lines.
- Motor loads and other loads require Q to convert the flow of electrons into useful work.
- When there is not enough Q power, the voltage sags down and it is not possible to push the power demanded by loads through the lines.