What is Power Factor?

Power factor is a measure of how effectively you are using electricity. Various types of power are at work to provide us with electrical energy. Here is what each one is doing.

Working Power – the “true” or “real” power used in all electrical appliances to perform the work of heating, lighting, motion, etc. We express this as kW or kilowatts. Common types of resistive loads are electric heating and lighting.

An inductive load, like a motor, compressor or ballast, also requires Reactive Power to generate and sustain a magnetic field in order to operate. We call this non-working power kVAR’s, or kilovolt-amperes-reactive.

Every home and business has both resistive and inductive loads. The ratio between these two types of loads becomes important as you add more inductive equipment. Working power and reactive power make up Apparent Power, which is called kVA, kilovolt-amperes. We determine apparent power using the formula, kVA2 = kV*A.

Going one step further, Power Factor (PF) is the ratio of working power to apparent power, or the formula PF = kW / kVA. A high PF benefits both the customer and utility, while a low PF indicates poor utilization of electrical power.

Why is Power Factor So Important In Electrical Power System ?

Generally, we can define the term power factor in three ways;

• The cosine of an angle between current and voltage of an Ac circuit is called power factor”
• The ratio between the resistance and total impedance of an Ac circuit is called power factor”
• The ratio between the active power and apparent power is called power factor”

Considering an inductive load, the power factor will be lagging due to which the current is lagging behind the voltage. While in capacitive load the angle goes opposite, the applied current angle is now leading before the voltage and consider as leading power factor.

The power factor plays an important role in ac circuits depending upon the load. As we know that lower the power factor, higher is the load current and vice-versa. *Lagging power factor has some disadvantages like large KVA rating because the KVA is inversely proportional to the power factor.

Similarly in lagging power factor the transmission lines must have greater conductor size due to which at low power factor the conductor carries a large amount of current.

Another demerit is the large copper losses, at low power factor the conductor carries large current

causes more IR2 losses. This results in poor efficiency.

The large current at low power factor causes greater voltage losses in alternator and transmission lines and with this effect, the system might reduce loading handling capacity as well.

Following are the causes of low Power factor:

1.Inductive Loads.Single phase and three phase induction Motors(Usually, Induction motor works

2.Varying Load in Power System(As we know that load on power system is varying. During low load period, supply voltage is increased which increase the magnetizing current which cause the decreased power factor)

3.Industrial heating furnaces

4.Electrical discharge lamps (High intensity discharge lighting) Arc lamps (operate a very low power factor)

5.Transformers

6.Harmonic Currents

7.Wind Farm

8.Solar Plant

Why improve low power factor?

Low power factor means lower operating efficiency which results in a need for larger conductors (wires) and increased equipment capacity, as well as causing voltage drops as power losses increase. These equate to higher capital investment, higher expenses, and diminished distribution system performance. Power factor correction actually does not save much energy (usually less than 1% of load requirements), and even that reduction depends on how low the power factor is to begin with and how heavily loaded inductive devices are in the distribution system. However, even though energy savings are minimal, correcting power factor can bring significant savings in energy bills if the utility imposes a low power factor penalty in their rate structure, as most utilities do for industrial customers. How much your company can save through installing power factor correction methods depends on your initial power factor, the level you correct it to, motor horsepower rating versus loading, and how the penalty charge is calculated by the utility. All of these variables should be considered when determining the payback potential for different power factor correction methods.

How much can I save by installing power factor correction?

Power factor correction provide many benefits:

• Reduced electric utility bills

• Increased system capacity

• Improved voltage

• Reduced losses

Reduced utility bills

Your electric utility provides working (kW) and reactive power (kVAR) to your plant in the form of apparent power (kVA). While reactive power (kVAR) doesn’t register on kW demand or kW hour meters, the utility’s transmission and distribution system must be large enough to provide the total power. Utilities have various ways of passing the expense of larger generators, transformers, cables, switches, and the like, along to you. As shown in the following case histories, capacitors can save you money no matter how your utility bills you for power.

kVA billing

The utility measures and bills every ampere of current, including reactive current.

• Fixed capacitor banks
• Low votlage Automatic capacitor banks
• Low voltage static var generator
• Medium voltage capacitor banks
• Medium voltage STATCOM