POWER CONDITIONERS FOR POWER QUALITY DISTURBANCE PROTECTION

Sunday, March 20, 2011

Power Conditioners (also called Line Conditioners or Power Line Conditioners) are devices that can mitigate power quality problems like voltage variations, voltage unbalance, line noise, harmonics, resonance and other power quality disturbances that could cost companies and even residences large amount of opportunity and damage expenses. It function to regulate, filter and/or suppress noise in AC power for electronic equipment and sensitive computers. Currently, there is no official definition for a power conditioner, power line conditioner or line conditioner, but generally it refers to a device that acts in one or more ways to deliver a voltage of the proper characteristics to enable load equipment to function properly.
Power Conditioners
Power Conditioners
Power conditioners could provide voltage regulation while others can correct a variety of other power quality problems. It is also common to find audio power conditioners that only include an electronic filter and a surge protector with no voltage regulating capability. However, as of now, no single power conditioner can correct ALL power quality problems.

Comparison of Power Conditioners
Comparison of Power Conditioners and Their Applications

Basic Specifications For Power Conditioners

Important specifications to consider when searching for power conditioners include:

Ø  Power Rating - this is usually expressed in volt-amps, which is the product of the maximum RMS voltage and the RMS current that the conditioner can handle.
Ø   Input Voltage - the nominal line voltage to which the conditioner is connected.
Ø   Output Voltage – the regulated or conditioned voltage.
Ø   Voltage Regulation Accuracy - the accuracy with which the output voltage is controlled.
Ø  Phase - General public or standard commercial voltages are typically single phase (e.g. computers, office equipment and laboratory instruments). Three-phase power is typically reserved for industrial use for machines that benefit from its efficiency (e.g. industrial motors).
Ø   Frequency - common choices include 50 Hz, 60Hz and 400 Hz. 


Considerations For Power Conditioner Selection

1.   Source Compatibility
Power conditioning equipment must be compatible with the intended power source to ensure its own operation and to avoid interfering with the operation of other loads connected to the same power source. Along with the obvious considerations (input voltage levels, number of phases, and frequency), it is also important to focus on the following subtle ones such as tolerance to sags, swells and surges, limited in-rush currents to prevent voltage sags, limited harmonic input current distortion and limited notching. If taken for granted, the power line conditioner may cause disturbances to other loads. For example, the rectifier of a static Uninterruptible Power Supply (UPS) may produce voltage notches that can cause sensitive loads to malfunction, despite the fact that it provides interruption protection for its load.

2.   Load compatibility
A power line conditioner must be compatible with the sensitive load. To ensure this, load's requirements must be known so that you can match them to a power conditioner with compatible output performance. As an example, if the load's allowable input voltage range is ±5% of nominal, then you don't need a precision voltage regulator to maintain output voltage to within ±1%.
Other considerations to take into account are size of the power conditioner and the basic specifications mentioned above. For instance, in sizing, it is important to account for large variations, as well as the waveform distortion of the load current. This is to avoid excessive output voltage variation and the heating effects.

3.   Applicability
Each power conditioner can be expected to protect against specific power quality problems. However, to get the best protection performance from each device, it is necessary to understand its respective application factors. Thus, it is essential to know the kind of power quality disturbance present in the area in order to determine whether the need is to regulate, suppress and/or filter the incoming power. Subsequently, the decision of what power line conditioner to use will be based on the required correction.

Additional Power Conditioner Features

The following additional features common to power conditioners


Ø  Medical Rating - Power line conditioners with medical ratings are designed and rated for medical or dental use - may include hospital grade ratings.
Ø Frequency Conversion - Line conditioners with frequency conversion include power conditioners that also convert input frequency to a different value (e.g. 60 Hz to 50 Hz converters).
Ø  Bypass Switch - Bypass switches for taking power conditioners off-line without physically removing them; allows unconditioned power to pass through.
Ø  Indicators or Readout - Readouts or indicators include visual display indicating status or performance; may include simple LED indicators or more elaborate readouts.


References:
Baggini, A. (2008). Handbook of Power Quality. UK: Wiley
Clark, J. (1990). AC Power Conditioners Design and Application
EPRI Solutions. (2005). Applying Power Conditioning Equipment
Utility Systems Technologies, Inc. (2009). Power Quality Basics

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I am an Electrical Engineer with a Masters Degree in Business Administration. My interest is in Power Quality, Diagnostic Testing and Protective Relaying. I have been working in an electric distribution utility for more than a decade. I handle PQ studies, power system analysis, diagnostic testing, protective relaying and capital budgeting for company projects.