PowerSight

Power Quality and Energy Analyzers for Safety, Speed, & Success

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Power Factor:  Understanding the Difference Between DPF and TPF

People often refer to power factor without understanding that there are two different power factor measurement types and that it is important to understand the difference between them.
If you have a power factor “problem,” it may mean that you have:

  • A power factor correction problem that requires adding (or taking away) capacitors.
  • A combination of a power factor correction and harmonics that makes it look worse than it is

But how do you know which problem you have? And how do you measure it?

 

What is Displacement Power Factor (DPF)?

DPF is what most people are thinking about when they talk of power factor.  For those comfortable with the math, it is the cosine of the angle between a driving voltage and the resulting current.  For the rest of us, it is a measure of how much the driven current waveform trails the driving voltage waveform.  It turns out that a few degrees of current phase lag makes very little difference in the power consumed, but as that lag increases, it has an increasing effect on lowering the power of the system.  It turns out that the relationship between increasing phase lag and the resulting lowered power is exactly expressed by the cosine of the lag angle.  Therefore, rather than reporting the lag angle, we usually report the cosine of the lag angle.  That gives a more meaningful understanding of whether you have a “displacement” problem or not.

 

That downward bending curve seen above for the true power is exactly the same as the downward bending curve of the cosine math function.  Therefore the cosine of the lag angle is an exact measure of how the true power decreases as the phase lag increases.

For this reason, rather than reporting the lag angle, we usually report the cosine of the lag angle.  That gives a more meaningful understanding of whether you have a phase angle “displacement” problem or not.  In a system where there are no harmonics present, the true power will be equal to the apparent power (the V x A) times the DPF:

 

W = Vrms x Arms x DPF  (when no harmonics are present)

 

What is True Power Factor (TPF)?

TPF is what most people are actually measuring.  It is simply the ratio of true power (KW) to the apparent power (KVA).

 

TPF = W / VA  (whether harmonics are present or not)

 

It’s easy to measure, and traditionally it is equal to the DPF (the cosine of the phase angle).  If your TPF is low, you have a problem.  The only question is whether the problem is due to current displacement or due to a combination of harmonic distortion and displacement.

 

Why You Care About DPF

If the DPF is low, then it takes more current to supply the same amount of power to a load.  We typically see this with motors, which are traditionally highly inductive loads.  Inductance causes the current to lag the voltage.

 

Here is an example of how this plays out.  Suppose a single phase motor that is running off 120V needs 1200W to run efficiently.  If there is no phase lag, then the lag angle = 0 degrees.  The cosine of 0 degrees is 1 and the required current draw will be:

 

1200W/120V/1= 10A

 

Now suppose that the motor has a very large inductance and as a result, the phase lag angle is 60 degrees.  The cosine of 60 degrees is 0.5, resulting in a current draw of

 

1200W/120V/0.5 = 20A

 

The required current for the same amount of work has doubled because of the increased phase lag.

 

Below are PSM-A waveform captures that illustrate what was just described.  The first circuit and the circuit below it are consuming nearly the same power, but the top one has a large phase lag of 60 degrees, resulting in a drop in DPF:

 

DPF = cos(60) = 0.50.

 

The circuit below it has no phase lag, resulting in

 

DPF = cos(0) = 1.00.

 

The circuit with the large phase lag requires about twice the amount of current (I1 = 20A) to supply similar power to the circuit with no phase lag (I1 = 10A)!

 

A single load with low DPF is usually not an important thing, but what if there are 1000 such motors?  Now the utility needs to supply twice the current to accomplish the same amount of work as if there was no phase lag.  The user doesn’t mind, because in most cases, they are paying for true power (KW) not the apparent power (KVA).  The utility is unhappy because now their distribution system is carrying twice the current that is actually needed to perform the work for the customer.  That extra current results in twice the resistive power loss in their distribution system, which benefits no one.  A similar problem arises for the end user if:

  • larger gauge conductors are required to supply the required amperage
  • the facility is remote and you supply the last miles of distribution yourself
  • the facility is geographically dispersed (such as for oil well pump jacks or distributed fluid pumps)

Since they do not want to absorb the cost of inefficiency, the utility fights back with a power factor surcharge on your bill so you will share their pain.  This surcharge can be pretty steep, so power factor correction circuitry may be a money-saving investment, in order to lower the required current and eliminate power factor correction surcharges (or lower the cable gauge requirements in your dispersed or remote facility).

 

Why You Care About TPF

First of all, TPF is often nearly equal to DPF, so if you care about DPF, you probably care about TPF.  The two measurements deviate from each other when harmonics are present.  In the modern era of non-linear loads and electronic power supplies, there can be significant harmonics present.  If the harmonic currents are not in phase with their harmonic driving voltages, then the true power (the KW) will be less than the apparent power (the KVA) and the resulting TPF will be lower than 1.00.

 

If you are monitoring a conventional motor without a VSD (variable speed drive) driving it, you will find that the TPF is a pretty good measurement of the DPF, so talking simply of “power factor” (PF) is pretty accurate and explanatory.  But if you are monitoring an electronic load with high harmonics, there is a good chance that the DPF (the phase lag of the fundamental frequency) is close to 1.00, even if the TPF is much lower.  Therefore, you should know your load before you make assumptions about what the TPF means.

 

To illustrate, below are waveform captures from two different single phase simulations.  Both circuits have a TPF of 0.93 with 12A. However, they are completely different situations, requiring completely different mitigation methods if you wished to raise the TPF higher.

 

The circuit on the left has no phase lag, but it has high current waveform distortion, resulting in W/VA= 0.93.  The circuit on the right has no harmonic distortion, but it has 22 degrees of phase lag, resulting in W/VA= 0.93.  The voltage and current RMS values are the same in both circuits. The W and VA are also the same, but they represent completely different challenges for mitigation.

 

Looking closer, we use PSM-A to view the harmonic distortion content of the two circuits.  In the results below, you see that the top simulation has THD for the current of 39%.  The bottom simulation has THD of 0%.

 

To complete this analysis, we use PSM-A to view the phasor diagrams for the two single phase simulations.  The top one has no displacement (i.e. DPF = 1.00).  The bottom one has 22 degrees of displacement (i.e. DPF = 0.93).

 

If you have high harmonic content, it may not matter.  A desk computer with a low TPF due to harmonics probably makes no difference to your facility.  But if you have 1000 desk computers with low TPF due to harmonics, you likely have substantial harmonic currents flowing through your facility wiring and through the distribution and step-down transformers at your site.  You care about this because harmonic currents have a heating effect that is far greater than currents of the same magnitude at the fundamental frequency.  So you may measure an overall current of 200A and feel safe, but your wiring in the cable trays and walls may be dangerously heated.  Your distribution transformers, if not properly K rated, may be overheating and in a dangerous condition, and there may be hot spots on contacts and connection points.

 

How PowerSight Helps You Know Power Factor

PowerSight has all the measurements you need to allow you to assess your problems and verify your solutions with regards to power factor.

 

All models measure and log TPF, the true power factor.  If you are monitoring an inductive load, this gives you a good measurement for the DPF, the displacement power factor, so you can take the proper mitigating measures.  If you are monitoring an electronic load, branch circuit, or service entrance you can get a sense of whether there is a displacement and/or harmonic problem present.

 

Most models also measure DPF and display readings on the analyzer itself so you can take a direct measurement, either while wearing your PPE with your analyzer in your hand or safely out of the arc flash zone, using the Remote Control feature.  All models allow capturing waveforms and then transforming them into phasor diagrams and harmonic bar charts to directly see the components of displacement and harmonics.  Our PS5000 and PS4550 power quality analyzers (with the AMO option enabled) allow you to also log the maximum, minimum, and average DPF into each log record for great analysis of the DPF as loads change.

 

All models (with the HAO option enabled) also measure and log the THD of each voltage and each current so it is clear if there is a harmonics issue or not.

 

How PowerSight Helps You Mitigate Low Power Factor Due to Phase Lag

Simple calculations can guide you to make the proper choice of power factor correction equipment and verify that such equipment is performing correctly.  All PowerSight models will log the true power (KW), the apparent power (KVA), the average reactive power (KVAR), and the true power factor (TPF).  The PS5000 and PS4550 with the AMO option will also log the signed DPF (showing positive and negative) so you can verify the actual phase lag (or phase lead) of current in each phase over time.  The PS5000 and PS4550 with the AMO option will also log the maximum, minimum, and average signed KVAR (showing both positive and negative) for accurate calculation of the needed capacitors and then for verifying that they are doing their job.

 

How PowerSight Helps You Mitigate Lowered Power Factor Due to Harmonics

All PowerSight analyzers will log the THD of each voltage and current so you can recognize and size the scale of your harmonic problems.  All PowerSight analyzers allow you to capture waveforms at any time and then transform the waveform into a harmonic breakdown of the magnitude of each harmonic frequency, so you can decide if you wish to trap specific frequencies or filter the full range of frequencies.  In addition, the PS5000 and the PS4550 with the AMO option will allow you to log each individual harmonic of each voltage and current so you can see how they vary with the series and parallel loads.  Logging individual harmonics can be beneficial in designing a harmonic trap for a specific harmonic.

 

When you mitigate, you will be able to verify the effectiveness of the mitigation by examining the log or waveforms.

 

Of course, if low TPF is the result of both harmonics and current lag, PowerSight will allow you to separate the two causes so you can take the correct mitigation action.

 

The ReportWriter Wizard of PSM-A can provide summary reports of before and after mitigation.  It can also provide comparison reports where the “before” and “after” are compared directly, with % improvement shown.

 

If you have suggestions on how to improve our equipment to improve your efficiency or to eliminate a source of error, please share it!  We are dedicated to your success.

 

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Single-Phase vs Three-Phase: Why it Matters

The Bare Bones

For non-professionals, this part is for you. The phase is the physical distribution of a load. Single-phase power is distributed through an AC (alternating current) power circuit with two wires, a phase wire and a neutral wire. Three-phase power has three wires instead of two, and sometimes a fourth (neutral) wire. Three-phase power is more sophisticated and difficult to measure but it allows for the distribution of larger power loads and keeps the delivery of the power more consistent than single-phase.

 

Why does it Matter?

Most professional facilities run on three-phase, while homes use a single-phase supply most of the time. If you are working in or managing a facility with a lot of power, you’re going to be running three-phase power. The reliability, consistency of power delivery, and energy efficiency is worth the extra work and complexity of three-phase. They also transmit far more power than single-phase (up to 200% more) with only 50% more wire. That being said, the power quality issues with three-phase power are a lot more complicated than single-phase, so you’re going to need an analyzer that can measure the appropriate parameters and communicate that data to you clearly and quickly. Devices like the PS4550 and PS5000 power quality analyzers specialize in that and are a great choice for three-phase AC power analysis. They also monitor split-phase, single-phase, multiple single-phase, DC (direct current), and 2CT/2PT – 3CT/2PT – 3CT/3PT metering circuits.

 

What Three-Phase Parameters Should get Measured?

There are a number of important power measurements that may be important to observe and gather data on. For voltage monitoring, sag/swell, unbalanced voltage, and transients are key issues to keep an eye out for. Similarly, current inrush (which can lead to voltage sags) should be captured and taken care of. Another big one is harmonics, which are easily measured with the right meter and can have implications in overheating and shortening the useful life of equipment. It is also beneficial to monitor power, in particular kW, kVA, kVAR, true power factor, displacement power factor, and peak demand. This can identify overconsumption of power and help save money spent on utilities.

 

PowerSight power quality analyzers measure all these elements and more with ease. Learn more on our products page or call our expert staff at (925)-944-1212.

 

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PowerSight Analyzer Remote Control

The PowerSight Manager – Advanced software has a Remote Control feature for the analyzer it’s connected to, allowing the user to use the meter as if it was in their hand. This feature is standard on every PowerSight analyzer through a Bluetooth wireless connection. This article discusses how it can be valuable and how to utilize it.

 

Advantages

There are many reasons to operate in Remote Control, but they summarize into 4 categories:

  • Safety,
  • Enhanced Viewing of Data,
  • Comfort, and
  • Efficiency.

 

Safety: This is the basic benefit of the Remote-Control ability.

  • Safety during initial setup. The Bluetooth connection allows for working with the meter while they are outside of the arc flash boundary zone. Depending on the environment, you may be able to wirelessly communicate with your PowerSight up to 30 feet from an exposed live panel.

  • Safety during tests: During a test, an analyzer is more often than not locked inside an electrical panel. In most cases, you can communicate wirelessly with the analyzer without opening the panel. This allows safely checking that the test is progressing properly and retrieving data sets along the way without the danger of opening the panel.

Enhanced Viewing of Data: Your data can be viewed in multiple ways. Each method has its advantages.

  • Real-Time Data View: You can view all the basic measurements of voltage, current, power, and power factor for each phase updated each second. The presentation can be done as a digital cascade of measurements, Matrix-style…

… or as a graph accumulating new data each second

  • Real-Time Meters View: You can view the basic voltage, current, power, and power factor measurements as a bank of analog or digital meters. Analog meters give you a feel for the magnitude of what is happening at a glance.

The digital meters show all the core measurements, updated each second.  In addition to the present value, they inform you of the average, maximum, and minimum values since you began viewing them

  • Waveform Views: Your laptop is the ideal place to view waveforms in high resolution

  • Other Views

Phasor Diagrams

Graphical and Digital Views of Harmonics

Comfort and Efficiency: Rather than suiting up with cumbersome PPE to check on your data or press the buttons of your analyzer, stay cool, comfortable, and safe outside the arc flash boundary zone. Avoid the distortion of face shields and clumsiness of gloves by operating the virtual keypad to accomplish what you need to. Save the time of opening and closing live panels and eliminate risk of injury.

How to Enter Remote Control

To use the Remote-Control ability, follow these steps:

  1. Open our PSM-A software.
  2. Connect to the analyzer
    1. How to connect to PowerSight via Bluetooth
    2. How to install a USB-to-Bluetooth Adapter
  3. Click the “Communicate” option
  4. Click the last option, “Remote Control”
  5. Begin using the meter like it’s in your hand!
    1. Check as much data as desired, but don’t change the test settings once the meter has begun monitoring a live study!

 

Still curious about Remote Control or other PowerSight products/services? Call us at (925)-944-1212.

 

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7 Reasons Hospitals Should Have a Reliable Power Quality Analyzer

Vote: Which is the Most Important Reason?

 

As of 2019, healthcare facilities in the US make up less than 5% of the total area in the commercial sector but consume over 10% of the total power (MDPI Energies Journal) and have to pay those bills.  In addition, advanced medical technology has increasingly sensitive power quality requirements. For those tasked with keeping the lights (and life-saving machines) running, having a dependable power quality analyzer on hand has tremendous benefits.

 

Briefly, a power analyzer is a power testing instrument that measures a wide range of power components, like voltage, current, frequency, harmonics, energy, etc. A power quality analyzer does all those things and also captures power quality events like swell, dip, transients, inrush, etc. Here are the seven key reasons why every hospital should own at least one good power quality analyzer.

 

  1. Ampacity and Load Verification

Whenever you want to add new equipment or even new outlets, you should be performing a (minimum) 72-hour power study to be sure that you can safely add the new load to the existing load. This study can be done easily with a power quality analyzer and it is often a legal requirement. Such studies are done for a reason, and knowing whether or not a new load will introduce problems is a critical piece of information for a healthcare facility that cannot afford to have equipment suddenly shut down. Ideally, once the study is complete, you will want to quickly generate a concise and informative report, investing a minimum of effort and time to create it. A report writing feature should be part of the software supplied with the analyzer.

 

  1. Evaluate the Quality of Power at Any Point

Advanced medical equipment may be quite sensitive to problems with the supplied power. You will want to be able to not only log the ongoing voltage and power delivered, but also to trigger on unusual events to see what was occurring when equipment malfunctioned. Preferably, you will want to have detailed sub-second information in several views in order for the cause of a malfunction to be identified. Surface-level power analysis is helpful but a power quality analyzer allows you to look deeper into the root cause of any power issue that may arise. Detecting power quality concerns early may also have a big impact on extending the useful life of a piece of equipment. You may also find it advantageous to test multiple distribution panels or tools at one time to compare activity between them and get a greater view of the power quality throughout the facility. Be sure the supplied software can display power quality events in multiple views.

 

  1. Verify and Evaluate Backup Power

Life-support equipment demands immediate power backup when utility power fails. The pass-off from battery power to diesel generators must similarly occur without interruption or surge. Finally, when utility power returns, the synchronization of phase and magnitude of the generated power must be sufficiently close to the restored utility power to avoid interruption or surge. A power analyzer can record the general timing and magnitudes of the transfers, but a power quality analyzer is needed to capture the electronic signatures and sub-second timing at the moments of transfer to see problems and ascertain the source of any issue.

 

  1. Evaluate Inrush Current

When breakers trip unexpectedly or equipment takes itself offline for no apparent reason, triggered capture of inrush current can reveal a signature that reveals if the problem is due to momentary excess current or to degraded breakers. It can also convincingly identify which equipment is the source of excessive inrush. Be sure the supplied software can provide ½ cycle RMS profiles of the inrush current to judge its characteristics.

 

  1. Evaluate Harmonic Distortion of Power

Modern electronic equipment often introduces harmonics into the power system. Although any one device rarely causes issues for other equipment or to the power delivery system, when there are many loads generating harmonics, safety issues can arise. Specifically:

  • some sensitive electronic equipment may have limits on the allowed harmonics of the delivered power,
  • harmonic currents can cause unforeseen heating in walls and raceways, or
  • harmonic currents will lower the load delivery capacity of the distributed power at your facility and can cause unsafe heating in the transformers. Excessive heating, as every facility director would know, leads to the possibility for fires and/or early equipment breakdown/malfunction.

 

  1. Reduce Power Costs and Perform Cost-Benefit Analysis

Evaluate the cost of power to existing equipment and the projected savings that come from replacement technology. With the cost of power being a large recurring cost of operations, getting the knowledge you need to shave a few percent from these on-going charges can quickly pay for your power quality analyzer. But first, you need to evaluate what the present costs are versus the actual benefits of replacement technology while in use. Be sure the software includes a report-generating wizard that presents before/after projected savings in both dollars and demand. This be key in making or justifying the correct decision. Furthermore, a power quality analyzer can identify the electrical equipment drawing the most power. Knowing where and how much power is delivered is invaluable knowledge that can help healthcare facilities save money on their electricity bill, freeing up more money towards saving lives.

 

  1. Special needs
  1. If certain equipment, such as high-resolution imaging instruments, require highly filtered voltage you may benefit from an analyzer that can measure the high frequency content of the power-line, above normal harmonic levels. The ability to measure the high frequency content of the power-line far above normal harmonic levels, up to 100,000 Hz, can provide a view of potential degradation wired directly into the equipment.
  2. If you manage your own distribution transformers, it can be beneficial to measure the medium voltage input to the transformers, typically 12,500 volts. If you can connect your analyzer directly to that high voltage, you can measure harmonics and sub-cycle transient events that may not pass through permanently-mounted PTs and metering step-down circuits.
  3. Similarly, it is not uncommon to operate 4,160 V motors in a high-power, high-efficiency operation. The ability to connect directly to 4,160 V can be very beneficial in evaluating the operation of the motor.
  4. If your facility includes DC equipment or battery banks, be sure your power analyzer has the adapters and range to cover the scale of your DC voltage and current needs.
  5. Advanced triggering abilities. Most power quality issues can be identified with half-cycle evaluation, but when you need special abilities, it is good to have them ready and waiting in your test equipment. The ability to trigger on non-cyclical events, such as switching transients or generated spikes of defective equipment, can solve finger-pointing controversies quickly and convincingly.

 

References:

Bawaneh K, Nezami F, Rasheduzzaman Md., Deken B. Energy Consumption Analysis and Characterization of Healthcare Facilities in the United States. MDPI. 2019. https://www.mdpi.com/1996-1073/12/19/3775/pdf

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Maximize Your Success with a High-Quality Power Analzyer

When you have a job to do, you want it to be done successfully. Success in power analysis is maximized by collecting and retaining the right data.  At each stage of the power analysis process, PowerSight maximizes your chances of success and minimizes/eliminates errors in the power monitoring process. We are one hundred percent committed to your success! That’s our commitment to you!

This all begins with PowerSight providing you and your company with the industry’s best accessories, options, and operating modes for power analyzers. You don’t need to settle! We are committed to providing Start-to-Finish solutions to measure and analyze almost any electric power system of any size anywhere in the world. Here’s what you need to know about us:

 

  1. We are the only major manufacturer to provide a direct connection to medium voltages. Why do we do it? Because our customers needed it!
  2. We were the first manufacturer to provide a Line-to-DC Converter, in order for our customers to power their meter off.
  3. We are the only manufacturer to provide power-line noise analysis up to 100 kHz. Again, we did this because our customers requested it.
  4. We offer the broadest range of AC current measurement, of DC current measurement, and of AC/DC voltage direct measurement of any manufacturer. You’d be hard-pressed to find power you cannot measure with one of our power quality analyzers!

 

And we aren’t done yet! We are working to expand our measurement capabilities because we believe there is always room for improvement.

 

We do more than just offer you a lot of options. We offer peace of mind for the most important element of any test: the data. Every meter has a generous amount of internal memory and SD card memory to provide redundant data storage. If the data in the meter is lost, the SD card is still available and vice versa.

 

Additionally, our built-in wizards and PSM-A software are designed to be hard to make a mistake. SureStart Expert System is a rules-based knowledge system that advises you in the plain language of any possible errors in the connections and setup of your meter before you start your test. The last thing you want to happen is to return in a month and not have the data you need!

 

If you have any further questions, remember that the experts at PowerSight are always here to help. If you need a new power quality analyzer but are not an industry expert, that’s okay because we are! We are here to support you every step of the way.

Just call (925)-944-1212 or email us at support@powersight.com with any further questions you have. You may also find what you’re looking for in our FAQs .

 

You need the right tools for the job to be successful. That’s what you’ll get by purchasing a power quality analyzer through PowerSight!

 

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How to Choose the Right Power Analyzer

 

You need a new power analyzer, but which one? There are so many available online, it can be overwhelming to try and decide. Power quality is assessed based on a number of power quality parameters. This is the place to begin. Today’s instruments usually handle the most common parameters such as voltage, sags/swells, current, energy, harmonics, and transients. It can be nearly impossible to know in advance the specific type of disturbance that gives rise to a fault condition. The more different types of disturbances an instrument handles, the more likely it is that one can identify the disturbance, or alternatively to exclude certain types of disturbances. Therefore, start your search with a power analyzer that can handle it all!

 

From there, it is important to consider the number of measuring points that should be included in the system. You certainly do not want a system with 5, 10 ,or 100’s of meters to take more time to deal with than a system that only includes 2 meters!

 

Also, consider how long you’ll want to be using this product. If you intend to work with power quality statistical in the long term, you should review the options available to analyze data over several years. And if you don’t plan to need this tool long term, remember that there is an option to rent your need power analyzer instead of purchasing it outright.

 

For reference, our Analyzers and Systems pages have comparison tables to help you narrow down which meter is best for you, based on features and measurement capabilities. For novice power monitoring, the PS2500 and PS3550 are the way to go. For high accuracy and complete power quality analysis, the PS4550 and PS5000 can’t be beat. Our systems vary by how much current and voltage is needed to be measured, and each includes its own analyzer.

 

Do you still have a lot of questions? No problem! Simply reach out to PowerSight and ask!
No one knows our products like us. This is because we design, manufacture, rent, and sell our own equipment. We’re the true industry experts! Simply fill out this online form and tell us a little about what you are looking for. Someone will get back to you soon with all the answers you need to make an informed decision that you’ll be happy with. If you prefer to speak with someone right away, you can also call (925)-944-1212.