Power Quality

Rockwell Automation Power Monitor

Power quality refers to the "cleanliness" of power reaching your equipment.  The two primary culprits that can degrade power quality are power factor and harmonics.  Power factor is caused by inductive loads, ie motors, old magnetic ballasts - anything that must sustain a magnetic field to operate.  Harmonics are caused by non-linear loads such as variable frequency drives, UPS systems, computer power supplies - anything that emulates an analog sine wave by breaking it into digital pulses.

Power factor can cost you money on your electric bill and rob your transformer of its full capacity.  Larger customers in the TVA region are penalized when power factor falls below 95% and smaller customers below 85%.  Power factor is calculated by dividing the real power used (measured in kW) by the apparent power (measured in KVAR).  Customers with lower power factors will pay a higher demand charge or a KVAR surcharge on their bill.

Harmonics, on the other hand, is not penalized on the electric bill and often goes unnoticed if not measured.  Excessive harmonics can lead to circuit breakers opening unexpectedly from heat build-up or failure of circuit boards in sensitive electronic equipment.  Harmonics are often exacerbated when power factor correction capacitors are installed to increase power factor in an effort to save money on your power bill.

Power quality measurement at the main switchgear and at key load centers in necessary to determine the power factor and harmonic levels at different points through the electrical distribution system.  From these measurements, power factor correction levels can be be determined with consideration for existing harmonics.  If harmonics are low, pure power factor correction capacitors will generally work.  If harmonics are moderate, coupling line reactors with the capacitors will generally suppress harmonics to an acceptable level.  If harmonics are high, special harmonic filters are generally recommended.

Another consideration to power factor correction is where to correct.  If capacitors are installed on the high voltage side of the service entrance, power factor will be corrected from a billing standpoint but not necessarily at the load center.  If correction is installed at the load center level, equipment life benefits from better power factor but project costs may be higher.

UtilEcon can provide measurement of power factor, harmonics and electrical loads at any point in your facility.  We offer systems design and project management services for most any sized power factor correction and/or harmonics mitigation project in the industrial sector on a project by project basis.