Power Quality: Definition, Why and How Do We Measure It?

What is power quality?

Definition

Power quality serves as an overarching term to capture the various phenomena impacting a user's equipment when the AC power deviates from acceptable limits. The stability of the electricity waveform is crucial, encompassing aspects such as amplitude, continuity, waveform shape, and frequency. A stable electrical supply ensures reliable performance of connected devices.

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A : Amplitude

Stability in the voltage RMS value

B : Continuity

No interruption to the waveform

C : Waveform

Clean in shape, not distorted

D : Frequency

Stability in terms of providing the same range of frequency values

When the quality of the power supply becomes compromised, the waveform can reflect symptoms of poor power quality. For instance, a phenomenon known as voltage swell (surge) manifests when voltage levels spike momentarily, potentially leading to damage or a reset of connected devices.

Why do we measure power quality?

Power quality issues can arise from various sources including natural events like lightning strikes, poor load distribution, and inadequate wiring or grounding. The increasing adoption of inverter technology, electric vehicle chargers, and renewable energy resources such as solar and wind introduces complexities to the power network, further impacting power quality negatively.

Poor power quality can lead to disruptions in transmission and electronic equipment, causing severe malfunctions. For instance, harmonic distortions may lead to overheating in reactors and generate noise issues in capacitors. Transient noise and voltage drops can halt the operation of computer-dependent control systems.

Both utility providers and end-users grapple with power supply problems stemming from inadequate power quality. However, pinpointing whether the origin of these issues lies within the supplier's or user's system can be challenging. Consequently, measuring power quality is indispensable for discernment of the underlying problems and for implementing effective counterstrategies.

How do we measure power quality

Standards play a pivotal role in measuring power quality, providing guidelines that ensure precise measurements and evaluations of electrical supply quality. They assist in identifying existing power quality issues and ensure compliance with quality and reliability benchmarks. Here are a few notable international standards governing power quality assessment:

IEC -4-30

A comprehensive standard outlining the methodology for power quality measurement, categorized into two classes—A and S. Class A measurements are deemed more reliable, demanding rigorous accuracy and specific algorithms for assessment.

IEC -4-7

This standard oversees the measurements of harmonic currents and voltages within power supply systems.

IEC -4-15

This represents testing techniques for voltage fluctuations and flicker, detailing measurement instrument prerequisites.

EN

A European power quality standard that stipulates limit values for supply voltage and additional characteristics.

IEEE

This encompasses recommended practices for monitoring power quality.

IEEE 519

This standard pertains to voltage and current harmonics.

Power quality analyzers are essential instruments utilized for measuring power quality attributes over extended durations. They document parameters such as voltage, current, frequency, harmonics, and transients, enabling professionals to diagnose power quality concerns, ensure compliance with established standards, and enhance electrical systems' efficiency.

Solutions from Hioki

At HIOKI, we offer a variety of power quality analyzers and power loggers tailored for commercial line power measurement.

Features of product model PQPQPW-21 include power and harmonics recording, compliance with IEC -4-30 Class A and Class S measurements, and IEEE 519 compliance.

As the movement toward sustainability and decarbonization accelerates, innovative grid-connected solutions are emerging, leading to increasingly intricate power sources. As these technologies proliferate, it becomes vital to assess their implications on power quality for both consumers and suppliers. The HIOKI power quality analyzer can assist in comprehending your power quality better.

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