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

What is power quality?

Definition

Power quality is a general term to represent the phenomena affecting to the user&#;s equipment when the AC power exceeds a certain limit. Fig. 1 shows the electricity waveform that serves as an indication of the quality of a power supply. It must be stable in terms of its amplitude, continuity, waveform shape, and frequency.

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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

Suppose for some reason, the waveform shown in Fig. 1 exceeds a certain limit, resulting in poor power quality. Then the waveform may look like Fig. 2, representing a phenomenon called voltage swell (surge), in which voltage rises momentarily. A surge in voltage may cause the power supply of the device to be damaged or the device to reset.

Why do we measure power quality?

Natural phenomena such as lightning strikes, poor load distribution, and wiring and grounding issues are a few examples of the causes of power quality problems. Inverter-based technology has become more common in recent years, as have grid-connected electric vehicle chargers and grid-tied renewable energy sources such as solar and wind power. These make the power network more complex and have a significant negative impact on power quality.

Poor power quality causes trouble in receptacle/transmission equipment and electronic equipment malfunctions. For example, harmonics are known to cause burn-out in reactors and generate defective noise in capacitors. Also, impulse or transient noise and voltage drops stop control systems that are dependent on a computers.

Power supply network problems caused by poor power quality is a common problem for both electric power suppliers and users. However, it is not easy to identify whether the cause of poor power supply quality is at the supplier&#;s system or the user&#;s system. Because of this situation, power quality measurement is necessary to understand the actual cause of power quality problems as well as to consider and analyze for effective countermeasures.

How do we measure power quality

Power quality is often measured based on standards. The standards serve as guidelines for measuring and evaluating the quality of the electrical power supply. They ensure that measurements are consistent, assist in identifying what types of power quality issues exist, and ensure that power systems meet specific quality and reliability standards. They provide guidelines for evaluating and enhancing the quality of electrical power. Here are some examples of the international standards for power quality.

IEC -4-30

An international standard stipulating how power quality should be measured. It classifies the measurement methods and capabilities of measuring instruments into two classes of A and S. The more reliable power quality measurement is Class A. The requirements for Class A are not only stipulated in terms of functions and accuracy, but also include detailed measurement algorithms and time clock accuracy.

IEC -4-7

An international standard governing measurement of harmonic current and harmonic voltage in power supply systems as well as harmonic current emitted by the equipment. The standard specifies the performance of a standard measuring instrument.

IEC -4-15

A standard that defines testing techniques for voltage fluctuation and flicker measurement as well as associated measuring instrument requirements.

EN

A European standard of power quality that defines limit values for supply voltage and other characteristics.

IEEE

Recommended practice for monitoring power quality.

IEEE 519

Standard related to voltage harmonics and current harmonics.

A power quality analyzer is an instrument that is used when performing power quality measurements. This instrument is used for measuring and analyzing various aspects of an electrical power supply for extended periods of time. It records data on voltage, current, frequency, harmonics, transients, and other parameters in order to analyze power quality. This allows professionals to diagnose issues with power quality, ensure compliance with standards, and optimize the performance of electrical systems.

Solutions from Hioki

At HIOKI, we provide a few types of power quality analyzers and power loggers that can be used for commercial line power measurement.

Product model PQPQPW-21PWPower and Harmonics recordingYesYesYes *1 Yes *2 Power quality measurementYesYesNoNoIEC -4-30 Class AClass S&#;&#;EN measurementCompliantCompliant&#;&#;IEEE 519CompliantCompliant&#;&#;Best forWhen you need to examine, diagnose, and countermeasure the power supply condition that causes issues in equipmentWhen you need to conduct a power survey to understand the load size in a system or to understand the power quality in a systemWhen you need to understand the power consumption of a facility or systemWhen you need to understand the power consumption of a facility or system

• *1:

  Up to 40th order

• *2:

  Up to 13th order

As the world progresses toward decarbonization and sustainability, the number of diverse grid-connected innovative solutions will expand, as will the complexity of power sources---not to mention the growth of inverter-powered energy-saving technology. As these trends become more prevalent, it is critical to examine how these factors affect power quality on both the consumer and supply sides. The HIOKI power quality analyzer will assist you in better understanding your power quality.

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Investigate and analyze power quality issues

Steady, high-quality power supply is not only about availability, but also about power quality. However, identifying the root causes of power quality issues&#;ranging from harmonic distortions and voltage fluctuations to the effects of lightning strikes and equipment failures&#;can be a complex challenge. These disturbances, often invisible to the naked eye, can lead to equipment malfunctions, operational downtime, and even safety hazards. Conducting a thorough power quality survey is the first step towards analyzing and mitigating these issues, thereby enhancing the overall performance of electrical systems.

This article provides useful tips and gists for conducting power quality surveys and analysis and identifying power quality problems. Whether you are a facility manager, an electrical engineer, or simply interested in electrical system optimization, these guidelines will serve as an essential tool in your efforts to ensure a stable and high-quality power supply.

The company is the world’s best Power Quality Meters supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Before Getting Started

Preparation is Key

Before diving into the measurements for a power quality survey, gathering detailed information about the site is essential. This foundational knowledge allows for a more accurate assessment and identification of potential improvement areas.

The following information must be collected.

Circuit wiring

Determine if the site operates on 3-phase or single-phase power.

Check for the presence of a neutral line.

Identify any mixed circuit wiring, such as 3-phase circuits divided into single phases.

Nominal supply voltage

Confirm the nominal supply voltage(s) &#; 110 V, 220 V, 440 V, etc.

Note if there are multiple power lines with different voltages, for instance, a higher voltage dedicated to the other A/C system.

Frequency

While most power supplies operate at 50 Hz or 60 Hz, exceptions exist. Specialized systems, like those in airplanes or ships, may operate at frequencies up to 400 Hz. It is crucial to verify the frequency of your power lines.

Current capacity

Grasping the current capacity within the system you're measuring is crucial. It aids in selecting the appropriate current sensors for the measurement, ultimately enhancing the accuracy and efficiency of your surveys.

Additional site information

Other information about the building, such as hours of operating key electronic equipment and what equipment has been added or removed, etc.

This comprehensive approach to pre-survey preparation ensures a thorough and effective power quality analysis, setting the stage for actionable insights and improvements.

Steps to Analyzing Power Quality Issues

Finding the root cause of power quality problems can be difficult. The following few tips can help with power quality measurements. Here are 4 tips to help you measure power quality.

1. What?

Understanding is the key to resolving troubleshooting caused by power quality problems. First, we need to know what type of trouble is occurring. A tip is to look for heat or unusual noises coming from the equipment.

2. When?

Next, it is necessary to know when the trouble occurred. Is it cyclical or intermittent? It is better if specific dates and times are known. If an event is recorded, the trouble could be caused by equipment that is running or restarting at that time of day. Knowing exactly what time the event occurred and when the trouble subsided will make it easier to determine which equipment or location caused the trouble.

3. Where?

The next step is to identify the measurement location. For example, if measurements are taken at a receptacle point, the trends in voltage and current may provide useful information. If both voltage and current are falling, the cause can be traced to outside the building. If the voltage is falling, it can be assumed that a short circuit or inrush current caused the problem inside the building. Simultaneous measurements at a number of locations can help identify the cause of the problem.

4. What may be the cause?

Finally, once the measurements have been completed, the root cause of the problem can be deduced. Sort power quality events by specific dates and times, and cross-reference them with site information such as equipment schedules and any recent changes in equipment (additions or removals). This approach can offer valuable clues to pinpoint the cause of issues.

Measurement Tools for Power Quality Analysis

For Measurement

To measure power quality, a specialized power quality analyzer is used. Hioki offers two types of analyzers: the advanced type PQ and the standard type PQ. Table 1 gives an overview of the two types.

Table 1: Overview of power quality analyzers

Product modelPQPQ

• PQ

• PQ

Standard compliance

• Power quality: IEC -4-30 Class A, EN , IEEE
• Harmonics: IEC -4-7, IEC -2-4 Class 3
• Flicker: IEC -4-15

• Power quality: IEC -4-30 Class S, EN , IEEE
• Harmonics: IEC -4-7, IEC -2-4 Class 3
• Flicker: IEC -4-15

Fundamental frequencyDC/50 Hz/60 Hz/400 HzDC/50 Hz/60 HzEvent parametersTransient, swell, dip, interruption, frequency fluctuation, inrush current, THDAdvance event capture features for troubleshooting:

• RMS values
• Voltage/current waveform peak
• Voltage waveform comparison
• Harmonics
• Unbalance factor
• Power
• Mains signaling voltage

N/AAdvance transient measurement: 2MS/s, 6 kVStandard transient measurement: 200kS/s, 2.2 kVBasic harmonics measurement

Harmonics 0 to 50 for V & I

Detect the DC element on the AC circuit (0th order).

Advanced harmonics measurementHigh order harmonics (Supraharmonics) : 2 kHz to 80 kHzN/ABest forWhen it is necessary to investigate, diagnose and countermeasure power supply conditions that cause equipment malfunctions.Where a power survey needs to be conducted to determine the load size of the system or to determine the power quality of the system.

For Analyzing

Measuring instruments are only for recording data, while software is needed for analysis. Let me remind you that both are important. The data acquired by Hioki's power quality analyzer can be analysed using software called PQ ONE.

Here are some useful features of PQ ONE in this area:

• 1.

  Event statistics

• 2.

  Event list

• 3.

  Trend graphs and event details

• 4.

  EN determination function

1. Event statistics

Displays event statistics by date or time. This function makes it easy to discover anomalies that occur at specific times of the day or on specific days of the week. Alternatively, anomalies occurring on specific days of the week can be easily detected

2. Event list

This feature allows you to view all captured events or filter them by specific occurrences, making it simpler to identify power anomalies based on duration and severity.

3. Trend graphs and Event details

Trend graphs give an overall picture of the measurement. Trend graphs make it easy to spot anomalies. Event details provide detailed information on the power quality events that occurred during the measurement. It provides details such as event magnitude, time, length and waveform shape. By analysing these data, clues to power quality problems can be found

4. EN judgment function

This function analyses the measurement data and judges whether or not it complies with the EN standard based on the voltage fluctuations in the trend section. Basically, it judges whether the power quality is good or not.

PQ One software also offers a convenient way to generate reports automatically with just a few clicks.

Finally

By clearly understanding what the true problem is, when and where it occurs, and the causes of those problems, you can take action to mitigate them and improve the power quality on your site. With Hioki&#;s power quality analyzer, you can diagnose even difficult-to-detect problems in power quality.Contact one of our experts today to find out more about how we can help you improve your production process.

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