Power Factor Correction in North Tipperary sites
Bill Analysis
An analysis of the County Council bills is carried out by the Tipperary Energy Agency on a regular basis. In 2009, an exercise was carried out on “Power Factor” issues in various sites in the Council.
The sites that were highlighted to have issues concerning their power factor include:
- Coolbawn Water Supply Facility
- Newport Water Supply Facility
- Nenagh Waste Water Treatment Facility
Definition of Power Factor Correction
In order to understand what the term Power Factor Correction means, further knowledge into electrical loads and distribution systems is required. Most loads in a electrical system fall into one of three categories; resistive (tungsten lamps), inductive (ac induction motors, fluorescent lighting) and capacitive (capacitors).
These 3 categories of loads perform differently when current passes through them. For example, with a resistive load the current stays in phase with the voltage but with an inductive load the current start to trail behind the voltage or “lag” the voltage. This is not a good thing.
When the current lags the voltage, there are losses because the system will draw more current than is necessary. In other words, the electricity companies have to supply far more current than is theoretically required and, in turn, transformers and cables have to be larger than normal to supply the extra wattless magnetising current.
The wattless part of the supply is known as the “reactive” element and “active” part of the power is the part that does the work i.e. the rating on your equipment. The relationship between these 2 parts of the supply makes up a right angled triangle. 
From this graph, it is obvious that if the Reactive Power is very big, i.e. there are a large amount of wattless units in the system, the apparent power or the power drawn from the grid as a result goes further and further away from the useful power or the power that is actually required to activate the loads in the system. Hence, the lower the reactive power the better.
The relationship between useful power and apparent power is defined by the Power Factor.
- Power Factor = Cos A = Useful Power / Apparent Power
Therefore, the smaller the angle A, the less Reactive Power (or wattless units). Ideally, the angle A is zero (i.e. no wattless units). However, a power factor of >0.95 is ok. Any power factor below 0.95 needs to be corrected through the installation of capacitors or power factors correction technology.
Implementation:
In the three sites outlined above, the annual savings is approximately €6000. Payback is <3 years.
