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15 February 2022
Shalini John

Why Is Power Factor Correction So Important for Green Buildings

Going ‘green’ is an ideal concept that is fast becoming a necessity, rather than a preferred option. In the global construction industry, there is an increasing drive to find means to integrate ‘green’ practices into building services. One of the prime areas where this can occur is in the field of building power consumption. In addition to using various alternative power sources, the efficient functioning of electronic appliances is critical. The extent of efficiency in electronic appliance functioning is further dependent on power quality, which is improved by power factor correction. With precise electrical design services, specifically electrical drafting services, and the use of active harmonic filters, smart MEP (M&E) engineering design for building services can contribute to the longevity of electronic equipment, resulting in decreased power consumption and reduced costs.

So, what is power factor correction?

Typically using capacitors to offset inductive loads, such as those produced by motors, power factor correction (PFC) tries to improve power factor and thus power quality. Ideally, a system should use all the power drawn from its source to perform useful work. This can happen if the current is in phase with the voltage. If a variation exists between the two, some of the energy from the AC mains is lost and does not perform work.

A measure of the effectiveness of using incoming power in electrical or electronic equipment is known as power factor. The technique of PFC attempts to achieve a power factor of 1 for any system, although most appliances will function effectively at a power factor of 0.95 also. Power factor is also known as the ratio of Real to Apparent power, terms which can be defined as follows:

  • Real power – power used to actually run equipment, perform work
  • Reactive power – power required by certain equipment, such as motors, relays, transformers, to create a magnetic field for the operation of the equipment, but does not perform work
  • Apparent power – vector sum of Real and Reactive power, total power needed to run the equipment

The efficient functioning of the power supply is increased with the use of PFC systems, resulting in cost savings on electrical consumption and supporting green architecture.

There are a number of reasons why the process of PFC may be needed, such as:

  • Failure of motors
  • Failure of electrical or electronic equipment or appliances
  • Continuous overheating of transformers, switchgear and cabling
  • Continuous and random tripping of fuses/circuit breakers
  • Equipment operation that is unstable
  • Increasing and undetermined high energy use and costs

Electrical equipment can become unstable and fail to work when the power factor is deemed poor. A system with a power factor of less than 90 percent will need power factor correction. Systems with poor power factors incur heavy energy costs, as an increased amount of current is needed to execute the same amount of work. Thus, improving power quality reduces power distribution system loads, reduces load on switching gear and cables, reduces costs.

To maintain systems that require power factor correction, the following levels should be regularly monitored, ideally every 6 months:

  • Power load reduction
  • Voltage levels
  • Harmonic content
  • Equipment condition
  • Functional operation

Now, traditionally, PFC equipment used a bank of capacitors to help reduce the total amount of electrical demand. The capacitors would offset an inductive load, or it would offset reactors in case of capacitive loads.

Enter the harmonic filter. A harmonic filter eliminates unwanted harmonics in electrical systems produced by non-linear loads, thus improving the performance of the equipment and reducing energy costs. Harmonic filtering is useful when the following situations occur:

  • Transformers, motors and conductors overheat
  • Generators show instability
  • Capacitors fail
  • Fuses and circuit breakers keep tripping
  • Drive failure/damage of sensitive electronic equipment
  • Increase in energy costs

Non-linear loads, such as uninterrupted power supplies (UPS), low-energy lighting and switched mode power supplies in personal computers, cause unwanted harmonic voltages and currents. By drawing current in short pulses, rather than a smooth wave-like manner, non-linear loads generate electrical harmonics, which create currents of varying frequencies that are reflected into the system, thus twisting the AC waveform.

It is in this way, by reducing the system’s efficiency, that harmonics reduce the power quality, leading to a lower power factor and ultimately higher energy costs. Harmonic filters sieve out a system’s electrical harmonics, reducing equipment overheating, tripping of fuses and breakers, improving power quality and thus reducing energy costs. By installing resonant circuits in series or in parallel, the harmonic currents are blocked or minimised, reducing harmonic voltage distortion.

The three main types of harmonic filters are:

Passive

  • Used in industrial sites with non-linear loads more than 500kVA
  • Used in sites needing power factor correction, reduced voltage and current distortion
  • An LC circuit is installed in parallel with the non-linear load. The circuit absorbs the harmonics, eliminating it flowing into the network.

Active

  • Used in industrial sites with non-linear loads less than 500kVA
  • Installed at sites that need reduced current distortion
  • Systems with power electronics are installed in series or parallel with non-linear loads, compensating harmonic voltage or current drawn by the load.

Hybrid

  • Combine the performance of active and passive filters

Harmonic filters thus contribute to ‘green’ buildings by improving power quality, improving power factors, reducing power consumption and, thus, helping leave a small carbon footprint and enabling low acquisition and life cycle costs. To enable construction to achieve a green building star rating, construction firms need to employ trusted engineering design services who are able to provide technically accurate electrical CAD drafting services. Rather than train and use in-house personnel, Western companies tend to seek cost-effective M&E services overseas. India, with its vast bank of qualified electrical engineers, is quickly becoming a preferred destination to seek expertise in power factor correction and other cutting-edge electrical design services that support green buildings.