Why should we improve power factor ?
Because there are following numerous benefits that can be gained through power factor correction:
1. Reduce Utility bill or kVA Demand Charges:
Electric utility companies may charge for maximum metered demand based on either the highest registered demand in kilowatts (KW meter), or a percentage of the highest registered demand in KVA (KVA meter), whichever is greater. If the power factor is low, the percentage of the measured KVA will be significantly greater than the KW demand.
kVA = kW / cosφ
Improving the power factor through power factor correction will therefore lower the demand charge, helping to reduce consumers’ electricity bill.
2. Increase Load Carrying Capabilities in Existing Circuits:
Loads drawing reactive power also demand reactive current. Installing power factor correction capacitors at the end of existing circuits near the inductive loads reduces the current carried by each circuit. The reduction in load current resulting from improved power factor allow the circuit to carry new loads or relieve an overloaded system, saving the cost of upgrading the distribution network when extra capacity is required for additional machinery or equipment.
3. Improve Voltage across the load:
A lower power factor causes a higher current flow for a given load. As the load current increases, the voltage drop in the conductor increases, which may result in a lower voltage at the equipment. With an improved power factor, the voltage drop in the conductor is reduced, improving the voltage at the equipment. A 10% drop in terminal voltage from the rated,
a. Will reduce the Induction motor torque by approx 19%,
b. Increase full load current by approx 11%,
c. Increase temperature rise by approx 6-7 degrees.
4. Reduced Power System Losses:
System conductor losses (P_{L} = I^{2}R) are proportional to the current squared and, since the current is reduced in direct proportion to the power factor improvement, the conductor losses are inversely proportional to the square of the power factor.
P_{L} proportatinal to 1/( p.f.)^{2}
5. Reduced Carbon Footprint:
Power factor correction results in less strain on the electricity grid, therefore reducing its carbon footprint. The lower demand on the electricity grid can account for reduction in carbon production.
6. Reduces kVAR loading on transformers:
For example, a 1,000 kVA transformer with an 80% power factor provides 800 kW (600 kVAR) of power to the main bus.
1000 kVA = √((800 kW)^{2} + ( ? kVAR)^{2})
So, kVAR = 600
By increasing the power factor to 90%, more kW can be supplied for the same amount of kVA.
1000 kVA = √((900 kW)^{2} + ( ? kVAR)^{2})
So, kVAR = 436
The KW capacity of the system increases to 900 KW and the utility supplies only 436 KVAR.