Power Quality Monitoring Part 1: The Importance ...

Abstract

This article discusses the importance of power quality (PQ) measurements in today's electric infrastructure and reviews areas of application for PQ monitoring. It will cover the IEC standard for power quality and its parameters. Finally, it summarizes the key differences between Class A and Class S power quality meters. A subsequent article will illustrate recommended solutions on "How to Design a Standards Compliant Power Quality Meter."

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The Need for Power Quality Measurement in Today's Electric Infrastructure

Power quality has gained renewed interest due to changing power generation modes and consumption dynamics. The unprecedented growth in renewable sources at different voltage levels has increased the number of PQ-related issues. Consumption patterns have also transformed widely due to unsynchronized loads added at multiple grid entry points and voltage levels. Examples include electric vehicle (EV) chargers that require hundreds of kilowatts and numerous data centers with related equipment such as heating, ventilation, and air conditioning. In industrial applications, arc furnaces running on variable frequency drives and switching transformers not only add unwanted harmonics to the grid but also cause voltage dips, swells, transient brownouts, and flicker.

Power quality in the utility space refers to the quality of the voltage delivered to the consumer, determined by regulations for magnitude, phase, and frequency. However, it denotes both voltage and current. While the generation side easily controls the voltage, consumer usage largely governs the current. The concept and implications of PQ issues are widespread depending on the end users.

Research and surveys show that the economic impact of poor PQ amounts to billions of dollars worldwide. Monitoring power quality directly impacts the economic performance of many business sectors. Although monitoring PQ efficiently and effectively at scale is challenging, it involves having highly trained personnel and expensive equipment installed at multiple points along the electrical system for long or indefinite periods.

Power Quality Monitoring Areas of Application

Power quality monitoring is often viewed as a cost-saving strategy for some business sectors and a critical activity for others. PQ issues can arise in various electric infrastructure areas. As we'll discuss, power quality monitoring is increasingly crucial in sectors like electric generation and distribution, EV charging, factories, and data centers.

Electricity Utility Companies, Electricity Transmission, and Distribution

Utility companies serve consumers with distribution systems, including generating stations and substations that supply electricity via transmission lines. Substation transformers step down the voltage, which injects harmonics or interharmonics into the system. Harmonic currents in distribution systems can cause distortion, low power factor, additional losses, and equipment overheating, leading to reduced equipment lifespan and increased cooling costs. Nonlinear single-phase loads deform the current waveform, causing additional transformer losses, increased neutral loads, and potential malfunctions of circuit breakers and electricity meters.

Wind and photovoltaic (PV) solar systems also cause several power quality problems when injected into the grid. Wind intermittency creates harmonics and short-duration voltage variations, while PV inverters produce noise that creates voltage transients, distorted harmonics, and radio frequency interference due to high-speed switching to increase energy efficiency.

EV Chargers

EV chargers face multiple power quality challenges both in power sent to and received from the grid. Power electronics-based converters in EV chargers inject harmonics and interharmonics into the grid. Faulty power converters can inject direct currents (DC). Fast EV chargers cause rapid voltage changes and flicker. From the charger side, faults in transmission systems lead to voltage dips or interruption, causing undervoltage protection activation and grid disconnection, resulting in poor user experience.

Factories

Power quality problems caused by supply variations and voltage disturbances cost industrial facilities in the U.S. approximately $119 billion annually. Similar financial losses occur in Europe. These costs link to downtime, production losses, and productivity losses. Degradation of power quality is often due to intermittent loads and variations from arc furnaces and industrial motors, causing surges, dips, distortions, interruptions, flicker, and signaling voltages.

Detecting and recording disturbances inside a factory requires power quality monitoring equipment at several points in the electrical installation or at the load level. Industry 4.0 technologies now enable monitoring power quality at the load level with industrial panel meters or submeters, providing a comprehensive view of power quality delivered to each load.

Data Centers

Most business activities depend on data centers for email, data storage, and cloud services. Data centers demand a high level of clean, reliable, and uninterrupted electricity. PQ monitoring helps managers prevent costly outages and manage equipment maintenance or replacement due to power supply unit (PSU) issues. Integrating uninterruptable power supply (UPS) systems into rack power distribution units (PDUs) is another reason to add PQ monitoring.

UPS system failure is the primary cause of unplanned data center outages. Outages can cost companies nearly $250,000 each. UPS systems ensure clean, uninterrupted power, but do not protect against issues generated by IT equipment PSUs, which introduce harmonic distortion and face interferences like voltage transients, swells, sags, spikes, imbalance, frequency variation, and poor grounding.

Power Quality Standards Defined

Power quality standards specify measurable limits for electricity magnitudes and their deviations from specified values. Different standards apply to various electricity system components. The IEC 61000-4-30 standard defines methods for measuring and interpreting PQ parameters of AC power systems at 50 Hz and 60 Hz. The standard also establishes Class A and Class S measurement devices.

• Class A defines the highest accuracy and precision for PQ parameter measurements, used for instruments requiring precise measurements for contractual matters and compliance verification.
• Class S is for power quality assessment, statistical analysis, and diagnostics with lower uncertainty. It reports a limited subset of the parameters and can be used on several sites or single equipment.

Note that the standard specifies measurement methods, result interpretation guidelines, and meter performance, but not instrument design.

Key Differences Between Class A and Class S Defined by the IEC 61000-4-30 Standard

Class A specifies higher accuracy and stringent requirements compared to Class S. Requirements include time synchronization, probe quality, calibration period, and temperature ranges.

Class A	Class S
Voltage Measurement Accuracy	±0.1%	±0.5%
Current Measurement Accuracy	±1%	±2%
Voltage and Current RMS Calculation	Half-cycle steps	One-cycle steps
Frequency Measurement Accuracy	±10 mHz	±50 mHz
150/180-Cycle Aggregation	No gaps, synchronized with UTC	Gaps allowed
Measurements of Harmonics up to Order	50th	40th
Time-Clock Uncertainty per 24 Hours	±1 second	±5 seconds
Time Synchronization	Required (GPS, radio, network signals)	Not required
Operation Temperature Range	0°C to 45°C	Specified by manufacturer

Conclusion

Power quality issues are prevalent across the entire electric infrastructure. Monitoring PQ helps improve performance, service quality, and equipment lifetime while reducing economic losses. The subsequent article, "How to Design a Standards Compliant Power Quality Meter," will introduce an integrated solution and platform to accelerate development and reduce costs for PQ monitoring products.

References

1. Panuwat Teansri, et al. "The Costs of Power Quality Disturbances for Industries Related Fabricated Metal, Machines and Equipment in Thailand." GMSARN International Journal, Vol. 6, 2012.

2. Sai Kiran Kumar Sivakoti, et al. "Power Quality Improvement In Distribution System Using D-Statcom in Transmission Lines." International Journal of Engineering Research and Applications (IJERA), Vol. 1, Issue 3.

3. Gabriel N. Popa, et al. "Some Power Quality Issues in Power Substation from Residential and Educational Buildings." 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE), IEEE, 2017.

4. Sulaiman A. Almohaimeed and Mamdouh Abdel-Akher. "Power Quality Issues and Mitigation for Electric Grids with Wind Power Penetration." Applied Sciences, December 2020.

5. George G. Karady, et al. "Power Quality Problems at Electric Vehicle's Charging Station." SAE Transactions, 1994.

6. David Lineweber and Shawn McNulty. "The Cost of Power Disturbances to Industrial and Digital Economy Companies." Electric Power Research Institute, Inc., June 2001.

7. Roman Targosz and Jonathan Manson. "Pan-European Power Quality Survey." 9th International Conference on Electrical Power Quality and Utilisation, IEEE, 2007.

8. Subrat Sahoo. "Recent Trends and Advances in Power Quality." Power Quality in Modern Power Systems, 2020.

9. A. El Mofty and K. Youssef. "Industrial Power Quality Problems." 16th International Conference and Exhibition on Electricity Distribution, 2001. Part 1: Contributions. CIRED (IEE Conf. Publ No. 482), IEEE, June 2001.

10. Ponemon Institute. "Cost of Data Center Outages." January 2016.

11. Uptime Institute. "Data Center Outages Are Common, Costly, and Preventable."

12. "IEC 61000-4-30:2015: Electromagnetic Compatibility (EMC)-Part 4-30: Testing and Measurement Techniques-Power Quality Measurement Methods." International Electrotechnical Commission, February 2015.

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