Power Factor Correction & Harmonic Filtering

Power Factor Correction in Non - Technical Terms

“A Power Factor Correction unit is an assembly of automated Capacitor Banks that introduces various capacitors into your site’s electrical load as the need arises to offset what is termed reactive losses at your specific site.

That is the technical definition but in essence it ensures that when your site reaches the peak on the once a month KVA demand Peak (30 min cycle), that this is at its lowest possible value.

A site may peak for arguments sake at 100 kva during the month. At this power demand level , it is stated as Max Demand (Total Power) = Active Power (used Kw) + Reactive Power (wasted kvar).

For illustrative purposes let say that for our example site that with its 100 KVA peak, the Load comprised of 90 KVA Actual (used) and 10 Reactive (wasted).

These figures are normally obtained from the sites online meters or in their absence mobile data loggers installed by ourselves for a period of a week or so, and are unique to every site. We use then to determine the potential savings as well as the required size (kvar) and specification of the PFC unit for the site, but for our purposes here we shall use the figures above.

This ratio of Actual to Total is expressed as a Power Factor, which for our example would be 0.9 (90/100).

Without to much technical jargon suffice it to say that the PFC (Power Factor Correction) Unit sole purpose is to compensate for this loss of 10kva.

If operational, this unit would therefore remove the wasted 10 kvar (or most of it, due to various technical factors absolute 1.00 is not always possible and therefore 0.98 or higher is deemed as a desirable range.)

A simple calculation would then translate to the same site instead of being billed for the 100 kva at its peak during the billing cycle, with the elimination of the reactive power, now peak at 90 kva. At a Tariff of R200 or higher per kVA in most municipalities across SA this means a R19 200 p.a. savings effected on your site’s annual Kva Max demand charges.

Needless to say the lower (worse) these sites power factor ratios are and the higher the KVA Demand tariffs are and become in future, the higher theses recoveries become hence there prominence in the property market for any user using in excess of 60 to 70A for their sites to utilise said PFC Units.”

Harmonic Filtering

In an ideal power system, the voltage supplied to customer equipment, and the resulting load current are perfect sine waves. In practice, however, conditions are never ideal, so these waveforms are often quite distorted. This deviation from perfect sinusoids is usually expressed in terms of harmonic distortion of the voltage and current waveforms. Power system harmonic distortion is not a new phenomenon - efforts to limit it to acceptable proportions have been a concern of power engineers from the early days of utility systems.

At that time, the distortion was typically caused by the magnetic saturation of transformers or by certain industrial loads, such as arc furnaces or arc welders. The major concerns were the effects of harmonics on synchronous and induction machines, telephone interference, and power capacitor failures. In the past, harmonic problems could often be tolerated because equipment was of conservative design and grounded wye-delta transformer connections were used judiciously. Distortions of the fundamental sinusoid generally occur in multiples of the fundamental frequency. Thus on a 60 Hz power system, a harmonic wave is a sinusoid having a frequency expressed by the following formula, where n is an integer: