POWER FACTOR CORRECTION 


Case study 1 – Rice Distributor Network operating company UKPN - London Reactive power charge at time of survey 0.329p / kVArh in excess of 33% of the kWh (i.e. a charge is imposed only if an average power factor of less than 0.95 is achieved) Available Supply Capacity (ASC) charge £0.93 / kVA / monthFrom the billing information the estimated maximum demand load vectors were as follows: kVA kW PF kVAr 2497 1923 0.77 1593 In order to correct the maximum demand condition to a more economical level of 0.96, 1000 kVAr of power factor correction was offered. With the above capacitors connected the maximum demand condition was predicted to be as follows: kVA kW PF kVAr 1992 1923 0.96 593 The reduction in maximum demand predicted = 2497 – 1992 = 505 kVA Potential annual savings From the above information, the following savings were calculated: Excess reactive power – on average the client was receiving £1500 / month in reactive power charges. By installing the equipment recommended this charge would be eliminated as an average power factor greater than 0.95 would be maintained. The potential annual saving is thus £1500 x 12 = £18,000. Available supply capacity – the reduction in maximum demand of 505 kVA represents an annual available supply capacity saving of 505 x 0.93 x 12 = £5635.80 Total potential annual savings = £23,635.80 Installed cost of equipment recommended The total installed cost of the equipment recommended was £20,612.00 Payback period of equipment From the cost of the equipment and the potential annual savings, the payback period of the equipment was calculated as approximately 10 months. Result of survey The equipment recommended was installed. The reactive power charges were eliminated and the client is in the process of renegotiating their available supply capacity.

What Is Power Factor Correction?


Power Factor (Cos φ) is the ratio of True Power (kW) to Apparent Power (kVA) and is used as an indication of how efficiently an industrial or commercial site is operating. The closer the Power Factor is to unity (1), the more efficiently a site is said to be operating. Generally, anything higher than 0.95 is said to be a healthy Power Factor and will usually be sufficient to avoid penalty charges on the electricity bill. However, there are times when it’s essential to operate as close to unity as practically possible to keep the current levels to a minimum to avoid tripping breakers on overload. The presence of Reactive Power (kVAr) in the system leads to a lower Power Factor. Equipment that requires a magnetic field to operate (traditional motors, chillers, induction heaters, fluorescent tubes, etc) will all draw current that is said to “lag” behind the Voltage; thus producing a “lagging” Power Factor – also known as an inductive Power Factor. The more inductive Reactive Power there will be on the system, the higher the Apparent Power will be and in turn the higher the total current drawn from the network will be. Reactive Power (kVAr) is the element that Power Factor Correction works to eliminate. The capacitors within draw current that is said to “lead” the Voltage, naturally producing a “leading” Power Factor – also known as a capacitive Power Factor. By having capacitors automatically switched into the circuit in equal measure to the nominally inductive site load, the two effectively cancel each other out. The result is that the overall Reactive Power levels are decreased and the Power Factor is improved accordingly.

PFC Maintenance


Annual Servicing Protects Your Investment


In order to continue to make savings on reactive power and availability charges, we recommend servicing power factor correction equipment at least once every year, sometimes more depending on your reliability on it. Capacitors can deteriorate over time. The dielectric inside breaks down the more they are switched, the longer they are in operation, and the more external events they’re subjected to. Therefore, keeping on top of the health of your PFC equipment is important to continue to operate at an efficient power factor (>0.95), the level at which charges will start appearing on electricity bills. It’s even more important if your PFC equipment is detuned. Capacitor deterioration will change the tuning frequency, which can result in harmonic magnification and/or absorption, and subsequently the loss of multiple capacitors in the same bank. The knock-on effect could be power quality issues that can mean other electrical equipment on site is affected. Find out how we can help take care of the annual servicing of your power factor correction equipment. As part of the service, we offer free reminders for scheduling maintenance visits so that they’re never missed. Contact us to see if we’ve been to your site before and when your service is next due.