Electric power quality
Compatibility between electric supply and connected loads.
Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications. Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady AC frequency close to the rated value, and smooth voltage curve waveform resembling a sine wave. The term describes the compatibility between what comes out of an electric outlet and the load that is plugged into it, and without proper power, an electrical device may malfunction, fail prematurely, or not operate at all.
- field
- Electrical engineering
- known_for
- Defining parameters of power quality: continuity of service, voltage variation, transients, harmonics
- key_parameters
- Continuity of service, voltage magnitude variation, transient voltages and currents, harmonic content
- common_deviations
- Swell, sag/dip, flicker, spikes/impulses/surges, undervoltage/brownout, overvoltage, frequency variation, harmonics
Lore & Background
The quality of electrical power is described by a set of parameters including continuity of service, variation in voltage magnitude, transient voltages and currents, and harmonic content in AC power waveforms.
Reader's Guide
Electric power quality is significant because it determines whether electrical loads function correctly, malfunction, or fail. The concept is often framed as a compatibility problem: either clean up the power or make equipment more resilient. The tolerance of data-processing equipment to voltage variations is characterized by the CBEMA curve. Power conditioning methods include uninterruptible power supplies (UPS), dynamic voltage regulators, surge protectors, and electronic filters. Modern smart grids use phasor measurement units to monitor power quality and respond automatically, supporting intermittent power sources and distributed generation. Power quality compression algorithms are essential for monitoring at critical sites such as hospitals and sewage treatment plants. The term 'power quality' actually describes the quality of voltage, not power or current, since power is simply the flow of energy and current demanded by a load is largely uncontrollable.
Did You Know?
- A 'dip' (British English) or 'sag' (American English) occurs when RMS voltage is below nominal by 10 to 90% for 0.5 cycle to 1 minute.
- The term 'brownout' originates from dimming of incandescent lights during system faults or overloading.
- High-quality UPS units use a double conversion topology that remanufactures an AC sine wave of higher quality than the original feed.
- Harmonics can cause vibrations, buzzing, equipment distortions, and losses and overheating in transformers.
More in Electrical Systems 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record