# Reactive Power

**REACTIVE POWER-INTRODUCTION**

Reactive power is usually explained with the vector mathematics or the phase shift sine wave graphs.

Reactive power is explained as when coil or the capacitor is connected to to an ac supply power,the coil or the capacitor stores electrical energy during one-fourth of an ac cycle.Then in the next quarter cycle the coil or the capacitor dumps all the stored energy back into the distant AC power supply.Ideal coil or capacitor consumes no electrical energy yet they create electrical current.

This reactive power is measured in the unit called volt-amps reactive**(VAR)** rather than watt.The mathematical symbol used for reactive power is** Q**.

**REACTIVE POWER – A COMPLETE DESCRIPTION**

Reactive power flow is needed in the alternating current transmission system to support transfer the real power over the network.In the alternating current circuits energy is stored temporarily in the inductive and capacitive elements,which can result in the periodic reversal of the direction of energy flow.The portion of the power flow remaining after being averaged over a complete ac waveform is the real power i.e.the energy that can be used to do the work and the electric fields due to inductive or capacitive network elements and then returned to the source is called reactive power*.*

Reactive power flow is needed in an alternating-current transmission system to support the transfer of real power over the network. In alternating current circuits, energy is stored temporarily in inductive and capacitive elements, which can result in the periodic reversal of the direction of energy flow. The portion of power flow remaining, after being averaged over a complete AC waveform, is the real power; that is, energy that can be used to do work (for example overcome friction in a motor, or heat an element). On the other hand, the portion of power flow that is temporarily stored in the form of magnetic or electric fields, due to inductive and capacitive network elements, and then returned to source, is known as *reactive power.*

AC connected devices that store energy in the form of a magnetic field include inductive devices called reactors, which consist of a large coil of wire. When a voltage is initially placed across the coil, a magnetic field builds up, and it takes a period of time for the current to reach full value. This causes the current to lag behind the voltage in phase; hence, these devices are said to **absorb reactive power**.

A capacitor is an AC device that stores energy in the form of an electric field. When current is driven through the capacitor, it takes a period of time for a charge to build up to produce the full voltage difference. On an AC network, the voltage across a capacitor is constantly changing – the capacitor will oppose this change, causing the voltage to lag behind the current. In other words, the current leads the voltage in phase; hence, these devices are said to** generate reactive power**.

Energy stored in capacitive or inductive elements of the network give rise to reactive power flow. Reactive power flow strongly influences the voltage levels across the network. Voltage levels and reactive power flow must be carefully controlled to allow a power system to be operated within acceptable limits.

**RELATED QUESTIONS AND ANSWERS**

1**.DEFINE REACTIVE POWER AND EXPLAIN IT.**

** ANS.**AC connected devices that store energy in the form of a magnetic field include inductive devices called reactors, which consist of a large coil of wire. When a voltage is initially placed across the coil, a magnetic field builds up, and it takes a period of time for the current to reach full value. This causes the current to lag behind the voltage in phase; hence, these devices are said to absorb reactive power.

2.**EXPLAIN MATHEMATICALLY THE TERMS ACTIVE POWER,REACTIVE POWER AND APPARENT POWER**

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The concept of reactive power is a prominent term for alternating current systems. The calculation for reactive power is different from active power as it also involves a cosine term.

This article also picks on the point as of why reactive power is calculated.

very useful reference for anybody those who prepare for public exams

important notes of reactive power with most asked question and solution is given..