What is reactive power? What is the use of reactive power?

In electric power transmission and distribution, volt-ampere reactive (var) is a unit by which reactive power is expressed in an AC electric power system.Reactive power exists in an AC circuit when the current and voltage are not in phase.

Reactive power is both the problem and solution to the power system network for several reasons. It plays an important role in the electrical power system for various functions such as satisfying the reactive power requirement, improving the voltage profiles, decreasing the network loss, providing sufficient reserve to ensure system security in emergencies, and other several functions. Let us discuss some of the reasons in brief, which makes reactive power so important.
1. Voltage Control
2. To Satisfy Reactive Power Demand
3. To Reduce Electrical Blackout
4. To Produce Magnetic Flux

What is Reactive Power?
It is the quantity that has become a fundamental concept to the analysis and understanding of AC electric power system. In general, this quantity is only defined for Alternating Current (AC) electric systems.

Uses

• 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.