Original Date: 03/17/1997
Revision Date: 01/18/2007
Best Practice : Power Factor Correction for Energy Conservation
In 1975, engineers at Polaroid’s Norwood Plant initiated a project to add capacitance to its inductive electrical load to increase the total power factor on its electrical grid. Typically, electric utility companies penalize commercial and industrial customers with a kilovolt ampere demand charge for poor power factor performance. Although the defining point of poor performance varies depending on the utility, poor power factor performance generally is defined within a range of less than 80% to 95% efficiency. The local electric utility company charges a demand penalty for power factor readings of less than 80% efficiency. Additional negative impacts of a continued poor power factor might include panel and circuit overloading or reaching practical kilovolt ampere limits of a substation.
The easiest way to correct power factors usually involves installing some type of capacitor bank at the main substation used by the electric utility company to determine the kilowatt hour usage and demand charges. Effectively, poor power factor performance within the plant is then transparent to the electric utility company for billing purposes. However, this is not the best method.
On its own initiative, Polaroid’s Norwood Plant raised its power factor and corrected any inefficiencies by installing capacitors on all motors greater than 25 hp at the motor, and capacitor banks in the motor control centers for all motors less than 25 hp. Capacitors were also added on all 15 kilovolt feeders within the plant.
Polaroid increased its power factor to more than 95% by installing capacitors on its inductive loads. In addition, this method efficiently uses Polaroid’s purchased electrical energy, directly conserves electrical energy, and reduces reactive power problems for the surrounding electrical grid.
For more information see the
Point of Contact for this survey.