How do you measure power quality at home?

Another method to measure power quality is to use an oscilloscope or a waveform analyzer to capture and display the shape of the voltage and current waveforms. This can help you identify any abnormalities or distortions in the waveform, such as harmonics, interharmonics, notches, noise, or flicker. Harmonics are multiples of the fundamental frequency that can cause overheating, losses, interference, or resonance in the system. Interharmonics are frequencies that are not multiples of the fundamental frequency and can cause similar problems as harmonics. Notches are sudden reductions in the voltage waveform that can occur due to switching or rectification. Noise is any unwanted signal that can interfere with the communication or control of the system. Flicker is a rapid change in the voltage amplitude that can cause perceptible variations in the brightness of lights. Waveform analysis can provide more detailed and accurate information about the power quality than voltage and frequency measurements, but it requires more sophisticated and expensive equipment and software.

With competitive price and timely delivery, SUIN sincerely hope to be your supplier and partner.

Defining Power Quality

Power Quality. What does it mean? In short, power quality measures how well a power supply&#;s voltage, frequency, and waveforms meet established specifications. It refers to the quality of voltage (rather than power or electric current). So, how do we determine whether it&#;s good or bad? 

Good power quality is a steady supply voltage that stays within the prescribed range, a steady Alternating Current frequency close to the rated value, and smooth voltage and current waveforms (comparable to a perfect sine wave). 

Therefore, bad power quality describes variations in steady supply voltage or frequency outside the rated range, usually measured in both magnitudes (the size of the excursion) and durations (how long was the value out of tolerance for).

Measuring Power Quality

Measurement and characterization of power quality have long been of interest to the electric power industry. As a result, the power industry developed standards to describe changes in power quality for different countries. 

Each country and continent adopts a combination of international standards and local derivatives to determine the quality of electrical energy:

• EN

   is the European standard for power quality, setting the acceptable distortion limits for the different parameters defining voltage in AC power.

• IEEE-519 

  is the North American guideline for power systems. Defined as &#;recommended practice,&#; and, unlike EN, this guideline refers to current distortion as well as voltage.

• IEC -4-30 

  is the standard defining methods for monitoring power quality.

All of these standards focus on the supply of utility voltage to an electrical load. Industry user groups further defined the terms and language of power quality when they defined a tolerance curve.

&#;

The Information Technology Industry Council (ITIC) created the ITIC curve in collaboration with EPRI&#;s Power Electronics Application Center (PEAC). They intended to derive a curve that can better reflect the performance of typical single-phase, 120 V, 60 Hz computers and their peripherals, and other information technology items like fax machines, copiers and point-of-sales terminals. The curve below has become the standard for defining power quality terms for consumers of electricity.

ITIC Power Quality tolerance curve

ITIC Curve creates four areas named by the action of the voltage and duration of the event:

Transients  are short-duration voltage changes that may be many times larger than normal voltage conditions. They last for such a short time that not much energy can be delivered. Transients last less than one cycle. In a 60 Hertz system like North America one cycle is 0. of a second or about 20 milliseconds.

Sags and Swells are slightly longer voltage changes with less magnitude change.

• Swells

   are a higher than normal voltage excursion that lasts between 20 milliseconds and 10 seconds.

   

• Sags 

  are lower than normal voltage excursion that lasts between 20 milliseconds and 10 seconds. Of the two, sags are more prevalent and typically cause the most impacts to sensitive loads connected to the grid.

Over and Under Voltages are longer-term voltage (>60 seconds) changes with a small magnitude change.

• An 

  over-voltage 

  is a higher than normal voltage excursion (typically 110% &#; 120% of nominal) for a duration longer than 1 minute.

• An 

  under-voltage

   is a lower than normal voltage excursion (typically 80% &#; 90% of nominal) for a duration longer than 1 minute.

Outages are simply long duration under-voltages where the delivered utility voltage drops to zero for longer than ten seconds.

Steady-state (long-term) conditions (to the right of the ITIC curve) are deemed &#;acceptable&#; if the delivered voltage is within plus or minus ten percent (+/- 10%) of the nominal value. In simple terms, if you measured the voltage at a receptacle it is acceptable if the measured voltage is between 108V (-10% of 120V nominal) and 132V (+10% of 120V nominal).

Contact us to discuss your requirements of Power Quality Meters. Our experienced sales team can help you identify the options that best suit your needs.

Utility Power Quality

The Federal Energy Regulatory Commission (FERC) is an independent agency that regulates the interstate transmission of natural gas, oil, and electricity. The FERC&#;s mission is to provide efficient, safe, reliable, and secure energy for consumers. In short, the FERC uses reliability statistics as quantitative metrics for measuring the quality of service provided by utilities.

FERC uses six (6) standard metrics defined by The Institute of Electrical and Electronics Engineers (IEEE):

1. SAIDI (System Average Interruption Duration Index)

SAIDI is an acronym that stands for System Average Interruption Duration Index. It is calculated by multiplying the average duration of customer interruptions by their total number and then dividing by the total number of customers served by the grid. Therefore, SAIDI describes the total duration of the average customer interruption.

SAIDI is an important metric to understand for demand-side customers. Further, it is the metric to start with when defining the electrical backup system&#;s expected time required to provide power.

For instance, northern California&#;s PG&E utility&#;s most recent () Annual Electric Reliability report shows that the SAIDI metric for the local San Jose area was much worse than the past five years.&#;

PG&E Utility Reliability Metrics for for San Jose Area

2. SAIF (System Average Interruption Frequency Index)

SAIFI is another acronym that stands for System Average Interruption Frequency Index. It is calculated by dividing the total number of customers interrupted in an outage by the total number of customers in the system. In short, SAIFI describes how often the average customer experiences an interruption.

For demand-side customers, this is another important metric to understand. The metric is used when defining the electrical backup system&#;s expected number of interruptions per year.

PG&E utility&#;s Table 23 above shows the SAIFI metric for the local San Jose area has increased (worse) more than 23% to nearly one outage per customer each year.

3. CAIDI: Customer Average Interruption Duration Index

The acronym CAIDI stands for Customer Average Interruption Duration Index. CAIDI is calculated by measuring the total minutes of customer interruption divided by the total number of customers interrupted. CAIDI describes the average time required to restore service.

The PG&E utility&#;s Table 23 above also reflects that the CAIDI metric for the local San Jose area is up to more than two hours of outage time per interruption.

4. CAIFI: Customer Average Interruption Frequency Index

CAIFI stands for Customer Average Interruption Frequency Index. It is calculated by dividing the number of interruptions by the number of customers experiencing interruptions. Therefore, CAIFI describes how many interruptions each impacted customer experiences.

5. MAIDI: Momentary Average Interruption Duration Index

MAIDI refers to Momentary Average Interruption Duration Index. This metric includes only &#;momentary&#; interruptions. For those customers who don&#;t understand the utility term &#;momentary,&#; this is typically a fault the grid responds automatically to restore service. IEEE further defines momentary disruptions as those lasting less than five minutes.

6. MAIFI: Momentary Average Interruption Frequency Index

MAIFI is the final acronym that means Momentary Average Interruption Frequency Index. Again, this metric includes only momentary disruptions that last for less than 5 minutes.

These metrics are found in the IEEE guide.

Why Measure Power Quality?

Simply based on the conflicting definitions explained above between the power quality terms used by consumers versus those used by the utility suppliers, it is clear power quality is an important measurement for both groups. Translating between the two groups is the real practice of electrical engineering that APT has specialized in for more than twenty years.

Customers who purchase and install generators, transfer switches, Uninterruptible Power Supplies (UPS), co-generation systems like solar (photovoltaics), fuel cells (like Bloom Energy), or energy storage (like Tesla PowerWalls) without understanding their utility reliability metrics often waste money.

Don&#;t buy these systems unless you understand that problem each solution is solving.

&#;

Our long experience with utilities and their customers has shown us that working to understand each other and solve problems together leads to lower costs and improved reliability for both sides.

Interested in measuring Power Quality at your business? 

 

Contact APT. We specialize in the measurement and analysis of Power Quality. We design solutions to save you money and maximize your reliability.

Andy Taylor PE, APT Chief Executive Officer

If you want to learn more, please visit our website Telecommunications Signal Generator.