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News Release from: PFC Engineering | Subject: Power factor correction equipment
Edited by the Engineeringtalk Editorial
Team on 05 March 2001
Big savings from power factor correction
equipment
Barry Oliver, managing director of PFC Engineering, looks at the influence power factor correction measures can have and how electrical contractors can steer customers toward these savings.
The Climate Change Levy looms large, but there is a way to save energy costs that large electricity users may be overlooking Barry Oliver, managing director of PFC Engineering Limited, looks at the influence power factor correction measures can have and how electrical contractors can steer their customers toward these savings
This article was originally published on Engineeringtalk on 16 Nov 2001 at 8.00am (UK)
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Although the Perkins Engines plant at Peterborough has always had power factor correction equipment, a survey of its substations found that, typically, the power factor was 0.8.
One does not have to be an avid consumer of muesli or even a Guardian reader to realise that we all need to do something to save good old planet Earth.
That was also the concensus of the governments of 147 countries that met in Kyoto in July 1996 to thrash out an agreement to reduce greenhouse gas emission targets for the year 2000 and beyond.
One of the UK's measures (emulated in most other European countries also) was to introduce an additional tax on fuel, called the Climate Change Levy.
The impending Climate Change Levy (CCL) will increase the electricity bills of most commercial consumers.
Understandably this has brought into sharp focus a broad variety of energy cost saving initiatives to offset the impact the CCL will have.
Further reading
High capacity power factor correction capacitors
A new range of power factor correction capacitors have been unveiled by PFC Engineering that provide high overload capacity, long life expectancy and safe reaction at overload.
Automatic Capacitor Modules for system builders
The new SBA Series Automatic Capacitor Modules consist of individual capacitor elements manufactured from metallised polypropylene or metallised paper and plastic film
Capacitor panels help meet new harmonic standards
PFC has introduced a range of detuned capacitor panels that make significant improvements in power factor correction and assist in meeting the newly introduced G5/4 Recommendations
The Government is to introduce Enhanced Capital Allowances (ECA) that enable the full cost of certain energy saving devices, when used in certain applications, to be written down against taxable revenue in the first year.
What is surprising to many in the electrotechnology field is that the issue of power factor correction has been completely overlooked in this context.
That having been stated, while there are no tax benefits for installing efficient and effective power factor correction measures, the fact remains that by doing so, many electricity consumers can reduce their electrical energy costs significantly.
Indeed, in some cases the single most expedient saving they may make, is in reducing the losses inherent in electrical distribution when substantial inductive loads are encountered.
Typical installations are, for example, in sites where there are lots of AC induction motors and so forth.
Ironically, the Inland Revenue can allow Enhanced Capital Allowances against the cost of installing variable speed inverter drives in such applications (provided they are for fans, pumps or compressors), but not for the installation of power factor correction equipment.
Of course, if the variable speed drive is set to run continuously at full speed (50Hz) there is no energy saving anyway, so it is beholden on the installers to reduce the speed of the motors in order to conserve energy! Whatever the debate over the manner in which ECAs have been assigned, it remains for industry to investigate power factor inefficiency where it might be present, since this is often a simply remedied way to effect electricity savings.
The installation is relatively straightforward and does not intrude on the productivity of the user.
Imagine the downtime required to fit variable speed drives to the hundreds of motors in an automotive paint plant! There are opportunities for electrical contractors to bring their customers advice on power factor inefficiencies and the countermeasures available to them.
While most contractors know what power factor is, explaining it to the senior personnel among customers is sometimes tricky.
With that in mind, here is a simple way to unravel the issue.
Power factor is the ratio of "useful power" to "total power" consumed by electrical equipment.
Any electrical equipment requiring the creation of a magnetic field to operate - such as AC motors, induction heaters and other transformer applications - will draw a current which is said to lag behind the voltage, thus producing a "lagging" power factor.
On the other hand, capacitors, contained in most power factor correction equipment, draw current that is said to lead the voltage, thus producing a "leading" power factor.
If capacitors are connected to a circuit that operates at a nominally lagging power factor, the extent that the circuit lags is reduced proportionately to the amount the capacitors lead.
Circuits having no resultant leading or lagging component are said to operate at a unity power factor - where the total energy consumed is equal to the useful energy.
So much for the basic physics lesson, there is more to consider.
Most commercial electricity users will by now have been notified by their regional electricity company (REC) that they will in future be subjected to an additional charge for reactive energy.
This reactive charge has been incorporated within electricity tariffs and agreements for many years, but has been dormant.
It is part of the "use of system" charge and is therefore not dependent upon the energy supplier.
Charges for reactive energy exist in two thirds of the REC areas.
Reactive energy is effectively the power used to energise the magnetic fields in motors, inductive heaters and so on.
While the useful energy is measured in kilowatts (kW), the reactive part is measured in kilovoltampsreactive (kVAr).
It is the aim when specifying and installing power factor correction equipment to reduce the reactive energy being drawn from the system.
Reactive energy substantially increases the energy losses on the local and national supply networks, including your customer's own installation.
This increased loss also applies to the customer's own transformers if they are a high voltage user.
Reactive energy also has the undesirable effect of reducing the output capacity of the network and transformers.
One thing to look out for in installations is that even where the user has power factor correction equipment installed, it might not be functioning adequately.
Remember the relationship between leading and lagging power factors.
If the capacitors are not functioning, the load has increased on the system, or indeed, if the original power factor calculations were incorrect, there could still be significant energy savings to be achieved.
It is wise to check the power factor equipment is adequately sized to meet the penalty levels now being imposed.
Remember that all capacitors have a finite life and older devices fail without warning.
Some old equipment may contain PCB and could be both hazardous and illegal, if unregistered.
Don't be fooled by the fact that contactors may still switch on and off and indicator lights may still illuminate even though the capacitors have ceased to operate.
Modern, high quality, capacitors have fail safe protection systems, which enable them to quietly disconnect themselves - again, failure goes undetected.
This leads on to an opportunity for those electrical contractors working with larger electricity users.
While most plant managers are aware of power factor correction, there is a surprising majority of these who do not have power factor correction equipment installed.
The installation is straightforward and inexpensive and the benefits are considerable - both in energy cost savings and environmentally.
It is not uncommon for industrial installations to be operating at power factors between 0.7 and 0.8 (that is, between 70% and 80% efficiency) - these will certainly all benefit from power factor correction measures.
Finally, there are further benefits to the customer in using efficient power factor correction equipment, in the form of increased power capacity and reduced losses on the network that can be attributed to the user.
Power factor correction equipment is often used to create additional capacity that was otherwise unavailable to the user.
In other words, they were able to extend their plant in spite of apparent restrictions in the electricity supply.
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