Accurate measurements of the electrical load profile of a potential customer are required to determine the most cost effective power factor correction solution.
Uncorrected power factor
The worse the uncorrected power factor, the shorter the payback period
The higher the target power factor, the longer the payback period
Power factor correction between 0.96 and 0.98 usually provides the best return on investment (there are certain exceptions where a target power factor of 1 is advisable).
Current and voltage harmonics present in the system. If these are elevated, blocking reactors might have to be fitted in series with each of the capacitor banks. This has a significant implication on the total cost of the power factor correction panel
Load changes (frequency and amplitude): if the load changes of an installation are significant ( i.e. mesh welding), thyristor controlled switching of the capacitor banks is then required as standard contactors are too slow in response
Other factors influencing the payback period are:
Target power factor: the “law of diminishing returns” applies: as the corrected power factor approaches 1.00, ever increasing amounts of reactive compensation are required for fairly small reductions in apparent power. A target power factor correction of between 0.96 and 0.98 usually provides the best return on investment (there are certain exceptions where a target power factor of 1 is advisable).
Equipment costs, determined by:
Quality of key components
Voltage (400/550V vs. 3.3/6.6/11/22kV)
Required protection of the power factor correction panel:
isolator (fused or not)
Ambient and operating temperature constraints
Protection (LV distribution)
Applicable maximum demand tariff levied by the power utility. In South Africa, there are significant differences in tariff. Herewith some examples (2012 rates):
Eskom Nightsave Urban (small) summer: R11.25/kVA
Ekurhuleni Tariff C summer: R68.03/kVA
JHB City Power (LPU LV Tariff) summer: R168.67/kVA