POWER FACTOR

Power factor:

In power system, three quantities are most important;

                1) Voltage

                2) Current

                3) Frequency

Power quality is an important concern in the power system because it affects the voltage, current, and frequency. The power factor is an important aspect for improving power quality of supply. A load with low power factor has good efficiency and it can save a considerable amount of cost. For, this reason, majority of the utility companies demand in the reduction of reactive power. If reactive power demand decrease, the power factor will improve.

 There are three types of power;

                1) Apparent power

                2) Active power

                3) Reactive power

 1) Apparent power: 

                               The apparent power is denoted as ‘S’. It is the product of the RMS voltage and current. Volt-amperes or VA is unit of the apparent power.

                                S = V x I                 for single phase apparent power

                                S = 1.73 V x I       for three phase apparent power

                                                                                Where V is phase voltage and I is line current

2) Active Power:

                               The active power is also known as true power or real power. This power is a useful power for the load. The unit of the active power is WATT (W) and it is denoted as P. WATT is a very small unit, so power is measured in kW or MW. The active power is carried out in the power system by the part of the current. This current is always in phase with the supply voltage. The real work cannot be done when the current is out of phase with the supply voltage.

3) Reactive power:  

                              The reactive power is a part of an apparent power which is out phase with the real power. This is happening in the power system by reactive elements like inductors and capacitors. This power does not use for the load. The reactive power is also known as the imaginary power. The unit of the reactive power is volt-ampere-reactive (VAR).

Power factor: 

                               The power factor is the ratio of active power (true power) to the power supplied by the power system (apparent power).

                                POWER FACTOR = REAL POWER / APPARENT POWER

                                                                          PF = P/S

In power triangle, θ is the angle between current and voltage. Power factor is also defined as the cosine angle between the phase voltage and the line current.

                                                                             PF = cos θ

Power factor is a dimensionless quantity. The range of power factor is between -1 to 1. In an ideal power system, the power factor is unity (1), means that there is only real power is available. There is absent of reactive power. But in the actual power system, we can not ignore the reactive power and it always is present in the power system. So, in the actual power system, the power system can not unity, but for good quality of supply, we try to maintain power factor near to the unity.

In the power system, we use FACTS devices to improve the power factor.