Power Factor is a measurement that compares the real power (watts) being consumed to the apparent power (Volts-Amps) of a load. A purely resistive load would have a power factor of 1.0

What does it do?

The power available to perform work is called real power (kW). Inductive loads such as motors, transformers, and high-intensity lighting introduce reactive power (kVARs) into a power system. The system capacity is rated by the apparent power (kVA) which must be large enough to accommodate both the real power (kW) and reactive power (kVAR). Since reactive power requires system capacity, but performs no work, utilities charge more for it and plants try to keep net kVARs low.

High reactive power translates to low power factor.

Power factor basics

• Utilities may charge higher rates or penalties for low power factor or high VARs.
• System capacity restrictions cause voltage drops and overheating.
• Inductive VARs can be corrected by applying capacitors or active conditioners.
  
  
  

How much does poor PF cost?

Assume the utility add 1% of demand charge for each 0.01 below PF of 0.97. Assume your PF averages 0.86 each month and your demand charge is $7000. (0.97 – 0.86) * 100% = 11%

(11% x $7000) x 12 month = $9,240

Avoidable annual cost

What to check?

• See if your utility rate plan imposes a charge for reactive demand or power factor.
• Find out how the utility measures power factor or VARs. For ecample, are they looking at peak intervals or average
• Identify loads that are causing lagging reactive power and develop a strategy for power factor correction.
  
  

How much is OK?

To avoid paying higher utility fees, power factor should be higher than  0.97, capacitors or conditioners may be applied on individual loads, at a confluence of several, or at the service entrance to improve power factor.

Power Correction

So a system with harmonic currents can cause overcurrent in correction capacitors. Plant maintenance staff realize this and often use a semiconductor-based device instead.

The device connected to each MCC, to continuously monitor circuit’s power factor.

It generates leading reactive power (VAR’s) to counteract the inductive, lagging VAR’s from the motors. It can respond instantly to load changes. In addition, it looks for any harmonic current and generates an inverted signal to cancel it. So to any upstream devices it appears as if the MCC is a resistive load.

FullSpectrum energy is a comprehensive Power Quality solutions Provider, offering bespoke solutions to mitigate power quality concerns saving money, downtime and enhancing productivity.

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Enquiries

Victor Oyedu, FNSE, FNIEEE, CPQ.
Power Quality and Energy Management Specialist.
Publisher at Afrienergyonline.com & 
CEO, FullSpectrum Energy Solutions Limited, Nigeria.