Measuring Efficiency of Power Devices: Transformers, Inverters – UPS systems, solar etc.

The measurement of efficiency is defined as “Power Out” divided by “Power In” expressed as a percentage. When measuring the efficiency of power conversion devices the instrumentation must measure the input power and output power simultaneously.  If the device under test is a three-phase unit then two power analyzers must be connected, one at the input and one at the output.  Each “Watts In” and “Watts Out” value must be taken at the same time to get an accurate computation of efficiency. How then should the two analyzers be synchronized?

This article suggests an approach that can give good results using standard power monitoring energy analyzers such as the PowerSight meters from Summit Technology, Inc. PowerSight meters have an internal clock that can either be programmed manually, or can be synched to a PC clock by linking to a PC.  Connecting each meter in turn to the PC will establish the two clocks are initially synched to the same clock.

If the efficiency test is performed at a constant load the input values and output values will be stable and can be noted and efficiency easily computed. This works best for a quick assessment; i.e  for tests that last only a few minutes and for computing a few power values.  If the objective is to test over a longer time period over varying load conditions, and for many computations, this next approach is recommended. (Good examples are such as testing UPS systems with load banks, so efficiency can be computed at various load steps between zero and full load. Or qualifying the efficiency of a transformer over a day.)

The input and output meters are programmed to log for the period of the test.  When the test is complete, the two data logs are downloaded using PowerSight Manager software and merged into Excel.  PowerSight Manager software makes the import into Excel very simple with just a single mouse click.  Before computing efficiency we want to ensure the Watts OUT and the Watts IN values are synchronized. Next, plot Watts for the two meters on the same graph, and inspect their profiles noting events such as step changes, or highest excursions.  If the two plots don’t quite track each other then shift one of the plots data in time, and adjust their time stamps forward or back in Excel until both plots on the graph track each other.  Once the two plots are synchronized the efficiencies at all points along the graph can be computed in Excel and its results plotted to understand how efficiency varies with load changes.

Power Quality 101 – An Explanation of Terms and Definitions

“Power Quality” conjures up mysterious terms like sags, swells, transients, and harmonics. Let’s explain what these terms mean.  PowerSight Power Quality Monitors are designed to record, measure, and report such power quality characteristics and events.

The concept of Power Quality aims to define the conditions that allow electrical systems to operate as intended, reliably.   What are the limits of voltage fluctuations and other power influences that would adversely affect the operational performance and/or reduce the reliability, or the life-span of electrical equipment?  This conversation describes such operational limits for electrical equipment, as well as the impact of power quality upon the supporting electrical infrastructure – conductors, transformers, breakers, generators, UPS systems etc.

Perfectly clean or pure power is rare since numerous users and loads share the same circuits and distribution systems and they each use, or consume, power in different ways. This inevitably alters the quality of power as neighboring loads and interconnected users will have effects upon each other. The goal of power quality is not so much to strive for the perfect sine wave but to control and manage power to ensure it is delivered efficiently, and of appropriate quality so that electrical equipment will operate reliably.

In electrical parlance “power” has a specific meaning. It describes the flow of energy in a circuit and is the product of voltage and current (and power factor in AC systems).  For the most part “Power Quality” refers to the voltage conditions with respect to time.  Most power quality measurements are made in the voltage domain.  However, the issue of harmonics – discussed here – often gets included with power quality investigations and harmonics measurements are made in both the voltage and current domains. There are occasions when when it useful to monitor in both the voltage and current domains simultaneously, so voltage disturbances can be correlated with current activity. For such comprehensive analysis the PowerSight PS4500 Power Quality analyzer has both voltage and current channels to give you a complete picture of the power situation in all domains: voltage, current, watts, and harmonics.

Sags – this a low voltage condition. Voltage sags are often momentary and last from a few cycles to minutes, or in the unusual case of a “brownout” last for hours.  A sag can also be referred to as a “dip”.  Most utility power companies follow the definitions that are established by technical committees such as the IEEE or IEC who define sags more rigorously; i.e.:  when the RMS voltage is below the nominal voltage by 10 to 90% for 0.5 cycle to 1 minute.  If the voltage dips below 90% for more than one minute many technical committees describe this situation specifically as an undervoltage or sometimes as a brownout.

Here are two examples recorded by a PowerSight PS4500 Power Quality Analyzer; a short-term sag of a few cycles presented in the sinusoidal domain, and a longer 5 second sag presented in the RMS domain.

Effects of voltage sags.
All electric machines and appliances must have an adequate voltage source.  If the voltage falls below a certain limit, usually specified by the manufacturer, the machine or appliance will mis-operate, or shut down and turn off, or become damaged.

Swells – this the opposite to a low voltage condition, it’s when voltage is suddenly increased. Voltage swells are often momentary and usually last just a few cycles to minutes.  Similar to sags, technical committees define swells as when the RMS voltage exceeds the nominal voltage by 10 to 80% for 0.5 cycle to 1 minute.

Effects of voltage sags.
When the voltage rises above a certain limit (usually specified by the equipment manufacturer) electrical equipment, machines, and appliances can malfunction, shut down and turn off, or become damaged.

Transients (Impulses) – these are very short duration bursts of energy on the power line that show up as brief, fast-rising voltage excursions on the sine wave.  You also may see the terms: “spike”, “impulses” or “surge” being used to describe these phenomena. They typically last for a few microseconds to several milliseconds and are caused by loads turning on or off. Most electrical devices will either require an inrush of energy to charge them when power is first applied, and conversely will discharge some stored energy when turned off.  The fastest rise-time, or briefest duration of a transient or impulse will be about one microsecond since the physics of electrical power conductors, i.e. their reactance, will not allow faster “bursts” of energy. The maximum voltage excursion of a transient could conceivably reach a few thousand volts.  Transients can also be caused by faults on the power system, or in the extreme by lightning.  Transients are insidious and unwelcome.  Why?  We can understand that very high-voltage, and high-energy transients will cause irreparable damage, such as lightning. The energy will literally evaporate components. At lower voltage and energy levels they do not cause immediate failure but tend to wear away and degrade electrical components over time. As components become weaker they become more prone and susceptible to failure at lower voltage levels. This sets up a vicious circle that gets progressively worse as components become progressively weaker. So its in the best interest of reliability to stop or attenuate transients and impulses before they reach your electronics and batter them to death!

Above is an example of a voltage transient:

ANSWER THE QUESTION; “IS MY POWER GOOD OR BAD?”
This application note will guide you through the steps to successfully perform a power quality study:
How to Conduct a Power Quality Study with the PowerSight PS4500 Power Quality Analyzer

Author: Michael Daish

SureStart: Making the Right Connection

SureStart confirmation

SureStart^TM Eliminates Connection and Setup Errors

It happens to the best of us! Discovering at the end of the study that the data is flawed or useless due to connection or setup errors. It’s a common problem that can be avoided when performing power monitoring studies by using a PowerSight power monitor with built-in connection-checking intelligence. Even the most knowledgeable professional can make errors in setup and connection. And even if the connections are correct, the wiring of the system may not be, and it is best to know that before the monitoring session has begun.

SureStart^TM is a technology that applies artificial intelligence to automatically identify what type of power system is present and identify what errors in connections or setups are probably present. It does this in three ways:

• It makes these determinations regardless of the power system type
• It does this even in the presence of multiple connection or wiring errors
• It presents the results in clear English statements.

Types of errors that may be present

Here are just a few examples of connection errors that SureStart^TM automatically detects when connecting a power analyzer to single-phase, two-phase, wye, delta, 4-wire delta, grounded delta, open delta, DC, and other power systems:

Plus, combinations of all the above listed errors.  SureStart gives you a simple text message in the meter window. You can double-check with the oscilloscope real-time waveform and phasor diagram to view signals and connections:

Real-time waveforms

Three phase voltage and current phasor

After making the correct connections the meter will give you a “Metering Connections OK” message, as shown above. Now you can continue with your power study with confidence.

Why Buy a PowerSight from Summit Technology instead of Fluke or Dranetz

There are several brands of power analyzers out there in the market. You’re probably curious to know what sets the PowerSight power analyzers from Summit Technology, Inc. apart from the rest of the field.  They all pretty much make the same power and power quality measurements, so there’s no significant distinction in terms of what they measure.  The difference is in how the meter or power monitor helps you perform your power studies smoothly, successfully, and safely.  Its all to do with the “user experience” – getting power studies done right, first time, and with ease. Let’s explain:

We should start by first appreciating that performing a power study is a process; a process that involves several steps as follows:

1. Suit up for safety as required by Arc Flash labels – or NFPA 70E rules.
2. Install monitor at monitoring location.
3. Connect voltage and current probes, and power supply, turn on.
4. Set up or program the power monitor to monitor power parameters, and set up power quality trigger limits.
5. Leave the monitor to record – for an hour, or day or two, or weeks.
6. Before retrieving the monitor suit up again with safety gear.
7. De-install the monitor and connections.
8. Download the recorded data to PC.
9. Analyze data, view graphs and events.
10. Generate a final report.

All the meters on the market do an adequate job in step 5 – the recording of data. PowerSight analyzers are superior because they also address all the steps in the process in more helpful and productive ways.  For example, in step 1, it is difficult to work comfortably when encumbered in an arc flash safety suit. The new NFPA70E safety rules demand that workers wear personal protective equipment (PPE).  See this: Electrical Testing Safety Paper.  These new requirements have radically changed how electrical maintenance work is carried out nowadays. To comply with these new requirements can be very confronting and onerous.  Wearing heavy, claustrophobic PPE is no picnic! It’s not easy to see clearly through the hood or visor.  Thick-fingered gloves interfere with dexterity and tactile feel when handing tools or locating and pushing tiny buttons on a keypad.  The PowerSight approach provides welcome relief from these challenges. PowerSight analyzers can be controlled by Bluetooth wireless up to 25 feet away. After installing the meter and connections workers can move to a safe distance  to remove cumbersome safety gear, and operate the meter remotely. From a notebook PC the operator can view waveforms, check connections, set up and program the analyzer, download and view power measurement data – all in improved comfort, and in greater safety!

Many a power study has been wasted or done incorrectly because of operator error in the connections and meter setup. PowerSight analyzers incorporate intelligent software, SureStart^TM, to check for errors and alert the operator with a specific error message before monitoring is started.  This feature makes a big difference in making sure every study gets perfect results, first time! For more details go here to read about: the benefits of SureStart^TM.

After the recording session is over the data is downloaded from the power analyzer and analyzed on a PC, steps 8 and 9. Summit Technology offers excellent PC software to control PowerSight meters, analyze the data and plot graphs – PowerSight Manager software (PSM). PSM also allows one-click export of data to Excel, and it will create final reports in Word or pdf files.  It is free of license restrictions and anyone can download it here: PSM Software. This makes the sharing of data and collaboration much easier as log files and power quality study files can be emailed and opened in PSM for analysis and reporting by others.

The Report Writer function is a tremendous boon to productivity for completing a power study.  It may not be readily appreciated that many loggers and power meters leave users stranded with large files of raw data.  To compile into a report takes multiple cutting and pasting operations which is tedious and time consuming. Not so with the PowerSight Manager software. This example of a final report with graphs and tabular data was done in a few seconds and a couple of mouse clicks: Power Study Report. If you need to repeat the study because you made changes to the load or circuit or panel, or have implemented an energy savings improvement and you need to verify how much kWh you saved, PSM is doubly helpful. The Report Writer can take two studies and compare them automatically and calculate the differences.  Talk about improved productivity! A “Before and After” comprehensive report is done in just a few clicks, instead of otherwise plodding through hours of manual analysis and calculations.

Once the report has been generated you have now successfully completed all the steps in the power monitoring process. Congratulations! Consider how smoothly it all went with a PowerSight meter that guides you along the way, checks your connections, enhances your safety, and creates a final report in a snap!  Oh, and did we mention that all the power data was captured too, with high accuracy and in great detail.

PowerSight technology is designed to assist the user with each step in the process to ensure overall success and therefore provides a far better “user experience”. We have paid attention to the human details of how the user behaves with a meter in the real world.  We understand the practical implications and safety challenges of installing and setting up a power monitor. These factors, plus the ease of reporting, small size and weight, CAT-IV safety rating, and SD card storage, distinguish the PowerSight analyzers from all others.

Buy or rent a PowerSight today!

Why a Harmonic Analyzer is used in Power Quality studies.

Power quality is important to understand and manage, crucial even since our modern technological society needs clean, dependable, reliable, glitch-free power to run our computers, machines, motors, lights etc. With our understanding of electricity we’ve come to realize that electricity can get “messed-up” on its way from the generation stations to us. It travels from generators at dams, coal plants, or nuclear power stations to your home or business via transmission lines at high-voltage. It then passes through one or more substations, and is eventually dropped down to usable voltages by transformers where we as consumers use or consume it. Keep in mind we have to share the distribution network with other users. As the electricity gets consumed by many users and loads it gets – in simple parlance – altered. The way we use power will affect other loads and our interconnected neighbors, and they will affect us. The degree of alteration – the power “quality” – depends on several factors but the amount of alteration can be measured by examining the voltage stability and fluctuations, and the harmonic content.  This is done with a power quality analyzer which usually will have a harmonic analyzer function – like the PowerSight power analyzers.

So what are power-line harmonics? These two graphs of voltage waveforms will illustrate:

The vertical axis is volts and the horizontal axis is time. The first one shows a power waveform that is sinusoidal and is an example of a nice, clean-looking, unaltered waveform that power generators produce.  The second graph shows a waveform that is choppy and distorted – it doesn’t look so clean does it?

A French mathematician named Fourier invented a method to analyze waveforms – the Fourier analysis.  It will show that the waveform on the left is made of one frequency – for power waveforms that would be 60Hz in the US (50Hz in Europe and other parts of the world.).  The analysis for the waveform on the right would show that besides 60Hz there is a jumble of other frequencies that mix, add, subtract, interfere, and alter the original waveform.  The analysis would show the mix of other frequencies and the amounts of their contributions, both in terms of amplitude (i.e. how big they are) and their phase position (i.e. at what point in time they are inserted into the mix) – as follows:

  The way to understand a harmonic table goes like this. The first harmonic is called the   fundamental and is declared to be 60Hz and its magnitude is 100%. The next harmonic (3.00) is the frequency of the fundamental multiplied by 3.00, i.e. = 180Hz.  It is 13% as large as the fundamental. So if the fundamental was 208Vrms then the third harmonic would be 13% x 208 = 27Vrms.  The next harmonic #5 is 300Hz and is 41.6 Vrms. The time duration of a power waveform to go through one oscillation is 16.666 ms. This equates to 60 times per second or 60Hz. Mathematically we can also express the oscillations as revolutions around a circle – which is a 360 degree rotation. The phase number tells us that the third harmonic (180Hz) doesn’t start at exactly the same time as the fundamental but is delayed by 42 degrees.

So why do we care about power-line harmonics? AC power distribution systems, and all the elements in a typical AC electrical infrastructure (conductors, transformers, breakers etc.) are designed to convey power efficiently at 6oHz. They are not so efficient at other frequencies.  By less efficient we mean that some of the power will not be transmitted but will be lost as heat.  The number one enemy of reliability is heat.  Operating life span is reduced, or the “wear and tear” is increased so component reliability is compromised.  If left unchecked or untreated, high levels of power line harmonics can cause transformers and conductors to destructively overheat, burn-up and fail, and for breakers and fuses to misoperate.

What creates the distortion of power waveforms?  To begin with, motors and incandescent lamps don’t generally create high levels of harmonics but electronic loads do. We generally refer to these latter types of loads as “non-linear” because the current waveform doesn’t follow the voltage waveform with the same shape.  Computers, computer-controlled equipment, electronic lighting and a plethora of modern loads are non-linear. Here’s an example of a computer power supply waveform captured by a PowerSight meter showing the current waveform is not sinusoidal like the voltage but a series of gulps of current, or pulses:

A power line harmonics analyzer can show you waveforms of the electricity at various locations inside your building or operation, and calculate the harmonics in both the voltage and current domains. There are guidelines specified by electrical engineers for acceptable levels of harmonic distortion – the one most commonly referred to is IEEE 519. Once you have an analyzer (and someone knowledgeable enough to use it), you can determine the extent of any harmonics.  If they fall outside of the recommended limits you can use the harmonic data to find an appropriate solution or strategy to minimize harmonic distortion.

Generally those measures may involve investing in devices that are designed to ‘clean’ or filter the power coming into your facility, or changing or moving the loads, or changing wiring or transformers to cope with levels of high harmonics.  The various solutions are situation (and budget) dependent.

A good power monitor or Power Quality Analyzer or Energy Analyzer will also perform as a harmonic power analyzer.

To summarize: Keeping tabs on power-line harmonics is prudent.  Use a harmonic analyzer in your operation or facility to check they don’t become excessive. As an analogy it’s like watching blood pressure or cholesterol to avoid health issues over the long term.  There will always be some level of harmonic distortion – you just need to keep it to a minimum.

Author: Michael Daish

Using an Energy Analyzer to Control Future Expenses

A portable energy analyzer can help you keep energy costs down.  Energy analyzers are essential tools for performing energy audits to identify where your energy dollars are going. There’s no getting around it – you can’t manage what you don’t understand, and in order to understand where and how power is being consumed you absolutely need to measure. Fortunately, with the advances in electronics the cost of portable analyzers has come down significantly making then very affordable. Plus companies such as Summit Technology also have energy analyzers for rental.

Energy savings initiatives start by establishing a baseline of energy use.  You want to pick a period of time that is representative of your buildings’ or operations’ business cycles.  This should be at least a week, and ideally a month, to match to utility bills for comparison.  The baseline data will show the activity of your power consumption, and the periods of maximum consumption. If your utility tariff penalizes you for “peak demand” charges you will want to know not just how big the peaks are but when they happened. With that knowledge its sometimes feasible to time-shift operations to reduce peak demand charges. You could also find out from your utility whether there is a more attractive tariff structure to take advantage of to lower your bill. In either case you will need the data from the energy analyzer to analyze those possibilities.

Some utilities also penalize large customers for poor power factor – again, check your rate schedule or tariff. Power factor is a measure of the phase relationship between voltage and current. If they are displaced too far from each other the utility generator has to pump more current into power lines to deliver more power. The penalties are designed to encourage their large consumers to adjust their loads to provide an acceptable power factor. (They don’t usually charge residential and small commercial users for poor power factor.) Typically consumers that have large populations of motors and other inductive loads will create low power factor unless it is managed. PowerSight analyzers measure all the power parameters you could possibly need in an energy audit. For sure you need to monitor volts, amps, watts and energy in kilowatt hours (kWh). PowerSight analyzers will also provide power factor, VA, VAR and frequency (Hz) logs.

Performing an energy audit often requires measuring at multiple points of energy use (at their circuits) to build a complete picture. For example, what is the % use of the lights, or of the HVAC system, or of manufacturing processes to the total consumption. Knowing these individual contributions can help you decide where to focus your energy efficiency improvements. Again, you can’t get around the fact that you must measure the use at each load or circuit to separate out the overall use from each “power guzzler”.  The data when plotted graphically will highlight how much power is being used throughout the day. You have to inspect the graphs to identify if power is being used when it needn’t be. You know the times of day when power use should be at zero or near zero, so focus on those time periods.

Maybe your HVAC is heating or cooling in the middle of the night when no one is around and a simple adjustment to thermostats or time switches would eliminate that waste. Maybe your lights are set to turn on across the entire complex at 6AM even though the only building being used right then is the administrative office.  Or they were still on at midnight unnecessarily and they could be better controlled by an energy management system or occupancy sensors. As each source of waste is identified and dealt with energy costs will be controlled.  These are simple examples but they illustrate how graphs of watts over time can help you see exactly what’s being consumed, day or night.

The baseline data captured by a PowerSight energy analyzer is viewed with powerful free PC software – PowerSight Manager Software (PSM). The software can generate a comprehensive power study report in a couple of mouse clicks. From PSM the data can be exported to Excel so that energy managers can play around with different scenarios to see where cost savings might be achieved. Files from PowerSight Energy Analyzers can be easily emailed to others such as energy companies, contractors, utilities, to review the data for help or assistance. This data is also essential for energy service companies to evaluate before submitting proposals for energy efficiency projects. The initial data should be kept because once the changes or a retrofit have been implemented a follow up study is often needed to verify, or fine-tune the new measures, to ensure they are yielding the expected savings.

In manufacturing energy use and production costs are related.  After all, energy is one of the components that goes into the manufacture of all goods. Monitoring can improve profitability. A good practice is to look at the “energy cost per widget” i.e. measure over a shift, a day, week or month how much energy is used to produce a certain manufacturing output. This could be done at the entire factory level, at a work area, or at a specific manufacturing tool. International companies use this approach to decide where it is cheapest to manufacture, as well as to compare how their world-wide operations compare against one another in manufacturing the same items.

Predicting cash flow, reducing operating costs, maximizing profits are part of any major corporation’s operations.  With a  dedicated commitment to energy auditing a business can make more efficient use of energy and plan their future energy expenditures. To fully realize all the savings for the future the energy auditing process must always be on-going. In order to give your business insight into optimizing its energy costs as operations grow, as business cycles ramp up, and other factors that change, just keep at it – keep energy analyzers in continuous use.  To save money you need the data!

Power Monitoring: Boosts Energy Efficiency & Power Reliability

How much electricity does the US consume as a whole — for everything that needs electricity: machinery, elevators, HVAC, boilers, computers, lights…the list goes on and on. Primary energy use in the United States in 2009 was 25,155 TWh (Terawatt hours); a TWh is equal to one trillion (10¹²) watts per hour.  It is estimated that the average business wastes upwards of 15% of it’s electricity, so there’s ample opportunity to curtail that waste and save money.  It would add up to a savings of about 4000 TWh – or 4,000,000,000,000 kilowatt hours (kWh).  If we assume an average kWh tariff of 12c/kWh it comes to a staggering $500 billion in round numbers, a year!

Energy conservation is not only good for the bottom line, we all know its good for the ecology of the planet. As a solid economic decision, businesses that look at all aspects of profitability in their operations will understand the prudence of examining and tracking their energy use. That’s why smart, cutting-edge businesses the world over are installing real-time power monitoring devices in their electrical systems. A real-time power monitoring system identifies where electricity is going and when, allowing business owners and operators to monitor behavior and take action more proactively.

Power monitoring can give clues as to what devices and systems in your building aren’t working at their peak efficiency and might need repair or replacement.  To be effective it must be done continuously.  In the ideal world every operation would have multiple meters on all their circuits monitoring power 365 days a year.

But what do you do when you don’t have a permanent, networked system of monitors?  You do the next best thing: deploy one or more portable power monitoring instruments to start getting a handle on your energy usage. A portable power monitor will tell you on each circuit exactly how much power it is drawing, and when, and help you identify which loads are the worst “energy guzzlers”.

Power monitors present data as graphs of power parameters plotted over time so the activity of loads turning and off can be easily be identified. Knowing when peaks occur can help you change equipment or process behaviors, or shift the timing of certain operations to reduce peak usage. You might also discover that some loads, such as heating and lighting, are on at 3AM every morning when noone is around.

Advanced power monitors also have power quality analysis capabilities.  Equipment that mis-operates or malfunctions due to poor power quality wastes $ and energy due to unplanned downtime, repair costs and the rework.  Power quality issues such as low voltage events due to other loads turning on, or transients that can disrupt or even damage electrical equipment can be identified at the same time the power consumption is being measured.  If high levels of power harmonics are present they will overheat conductors, transformers, and panels leading to premature failure,  more expensive downtime, more rework, and extra energy costs. Energy efficiency and power reliability are inextricably linked.  The good news is that an advanced power monitoring device such as the PowerSight PS4500 can perform double duty and audit both energy use and power quality.

Often, deploying portable power monitors is a prelude to developing a real-time 24x7x365 permanent monitoring system to continue to track and improve energy usage. If the system is being installed in several “trenches” portable monitors can help plan the priority of monitoring locations as the system is expanded.  Inevitably, situations arise where individual loads’ or circuits’ power profiles need to be measured because the permanent monitor can’t provide the granularity of data.  Thus portable and permanent monitoring are adjuncts to each other. Keep in mind that most permanent monitoring systems are optimized for energy use, not all of them are set up for power quality too. If you have or are planning a permanent system, that’s smart, but it would be prudent to also keep a portable power monitor handy.

Or, you can always rent a portable power monitor when the need arises.

Why You Need a Power Analyzer

A power analyzer is an important tool for electrical engineers, contractors, and industrial maintenance technicians.  A power analyzer can help save money on the electric bill and reduce energy costs by quantifying and identifying where and when power is used. By understanding the times of peak usage you can then choose to modify system performance or behavior to use less electricity, or determine whether the machine or appliance needs to upgraded or changed for newer technology that will operate more efficiently. It’s not easy to assess how to reduce energy consumption unless energy audits are performed as shown in these sample power audit reports from the PowerSight power analyzer from Summit Technology, Inc.

Further, if the power is unstable, or experiences interruptions and glitches that disrupt computers and other operations, the more sophisticated power analyzers can measure power quality and capture power disturbance events in detail.  Then it becomes easier to identify whether the problem was caused by the utility supply, or more likely, is due to events and disruptions that commonly occur inside the factory, office, or building operation due to the variety of equipment that repeatedly turn on and off. Electrical power quality will be affected – i.e. become more “polluted” the further the point of use is from the generator, and in proportion to the number of users and loads who must all share the same circuits and wires.  The degree to which power quality has become degraded can only be quantified with a Power Quality Analyzer. There are many power quality problems such as: harmonics, voltage dips or sags, outages, surges, transients, noise, and impulses – and consequently many different solutions.  The best solution can only be chosen correctly after a rigorous analysis of the situation by a power analyzer.

Besides identifying power use and the “energy guzzlers” in your operations, or testing whether “bad power” is causing malfunctions and breakdowns of equipment, a power analyzer is more often used for simple load studies.  Industrial engineers, for example, must often perform load and panel studies whenever they want to add a new circuit, or a new load to a circuit, or make sure that circuits and panels are not overloaded that would cause breakers and fuses to trip. Electrical codes state that circuits and panels must only carry up to 80% of their maximum rated capacity.  An initial study is performed over 72 hours or a week to record the voltage and current behavior on a circuit, or at a panel, transformer etc. The data is plotted as a current graph to help determine whether there is room to add more load.  Once the new breaker, or circuit, or load has been added another study should be done with a power analyzer to make sure the 80% rule has not been broken.  Load studies of are often referred to as “logs” and thus a power analyzer may sometimes be described as a power logger or data logger.

Power analyzers can go by different “marketing” labels such as data logger, power monitor, power meter, or power quality analyzer so it is important to study their data sheets to compare capabilities and functions.  Summit Technology, Inc. has a program to allow you to rent a power analyzer so you can try before you buy.  You can also trial free Power Analyzer Software.

The Purpose and Power of Energy Auditing

Energy auditing — is the process of evaluating energy use or power consumption, with the objective of saving energy and reducing costs.  Energy audits help institutions, corporations, industrial, government operations and even the occasional private residence to reduce their energy consumption. In addition to saving money on energy costs, the strain on the grid is reduced, plus pollution and CO2 emissions are lessened.

The ultimate goal of an energy audit is to make a process or facility more energy-efficient. To identify possible energy savings opportunities one or more power studies must be carried out.  There are many energy savings strategies and technologies to choose from, each is situation dependent. Some are simple such as installing double-paned windows in a home or building to keep the heating bill down, or retrofitting more efficient lamps.  In a complex industrial process energy is used for many tasks, such as for heating and cooling , for powering motors and pumps, running machines and computers etc.  Energy savings can be achieved by changing the way the process is controlled or by replacing older equipment with newer, more efficient technologies. Before any energy savings strategy can be implemented the potential savings need to be evaluated.  This starts with collecting data on the present power usage and then calculating different energy savings scenarios to pick the optimum approach.  Thus the purpose of the energy audit is to provide the initial data. An example of an energy audit is shown in this power study report.

Carrying out an energy audit means installing an energy analyzer that collects data on voltage, current, power and energy.  Energy audits may be taken at multiple locations in complex operations or large facilities, either with multiple analyzers, or by moving an analyzer from location to location over days and weeks.  Usually an initial study is carried out at the point where utility power is connected – the service entrance, or the point closest to the utility billing meter. This initial study should be done over a month, ideally, to compare with the monthly utility bill.  The initial study will give an overall view of total energy use and when the maximum usage occurs.  To fully evaluate possible energy savings measures more detail is needed, so further audits are done to separate the energy usage of  the various “power guzzling loads” such as lighting, air conditioning and heating, motors, as well as at any specific industrial process or machine.

Energy auditing might include:

• Evaluating the age of existing appliances and machines for replacement with newer, more energy efficient ones.
• Ensuring that maintenance procedures for major systems to maintain efficiency are being followed (e.g. did you properly maintain HVAC systems by changing or cleaning clogged air filters?)
• Eliminating as far as possible obvious energy-wasting culprits, such as inadequate insulation in walls, roofs, and ducts, poor door seals, leaky windows, water being left to run etc.
• Projecting the monthly savings that can be had from performing a particular renovation or replacing an inefficient machine.
• Planning out a behavior set that encourages saving energy, like turning lights off or using occupancy sensors.
• Installing an energy management system or other controls that control A/C systems or office lighting that turns off automatically after normal work hours.
• Changing to an alternative source of energy such as an on-site generator, photovoltaic panels, or wind turbines.

An energy auditor who performs a rigorous audit will utilize a variety of specialized equipment to build a complete picture. From energy monitors to some extraordinary gadgets like thermal cameras which can identify where heat is escaping.  The entire energy auditing process can take many weeks if you have a large or multiple structures to audit.

Its possible that there may be still some operations where an experienced auditor can identify overlooked opportunities by simply walking through a facility, noticing old lights that could be changed and 20 year old machines that are inefficient.  These days any “low hanging fruit” may be harder to find so the game typically involves carrying out power studies with a power monitor and making actual measurements, then evaluating solutions.  After an energy savings measure has been implemented a follow up audit needs to be done to verify the savings are being realized. The verification audit is often necessary to receive rebates from utility company energy savings incentive programs. Fortunately, powerful reporting software makes the task of producing the “before and after” results in a professional-looking report a simple matter of clicking a mouse.

From that point on, more savings accrue, it’s all money in the bank!

What to Expect from a Portable Power Monitor

A portable power monitor is a in instrument that performs the same measurements as the utility power meter at your business or operation, but in much more detail and scope, as in these examples of power study reports. It can give you a lot of very useful information about the way your business or operation uses electricity. Usually the utility meter just provides a number that the utility company bills you for; the energy in kilowatt hours (kWh) for your entire facility.  (Note: the new “smart meters” now being installed can supply much more information than the older rotating-disk types.)

However, the utility meter doesn’t tell you when the power use is at a peak, and is fixed in one location.  If you want to understand the energy use of other parts of your operation or facility, such as the lights, or HVAC, or manufacturing process, or of the computer room, you will have to install a portable power monitor at those circuits.

With the right type of power monitor you can also find out if your power is clean and stable, and even report when the power “hiccups” or fails.  The technical terms for such hiccups in power quality parlance are: sags (or dips), surges, transients, impulses, and power failures. More information on power quality terms are here: Power Quality Terms & Definitions.

Multiple Functions

A portable power monitor may have some or all of the following functions:

• A real-time meter display to show present values of voltage, current, Hz, watts etc. like a multimeter for spot measurements.
•  A data logger function to record power values over time with PC software to analyze and present the recording history graphically.
• A harmonics analyzer to measure and record power-line harmonics.
• A power quality function for recording voltage disturbances such as voltage sags and dips, surges, transients and impulses.
• Voltage and current input channels to measure both single- and three-phase power.
• Internal memory for storing power data for up to a month or more.

Additionally, some power power monitors like the PowerSight meters from Summit Technology, can measure both AC — alternating current, as well as DC — direct current.   While the majority of applications are for 60Hz and 50Hz AC power there are some specialized power systems such as in the military and on aircraft that use 400Hz or 415Hz AC power.

Safety

New safety rules are now in effect to protect electrical workers from injury and Arc-Flash hazards.  These rules are defined in NFPA 70E (CSA Z462 in Canada).  Consequently, when using a power monitor make sure it has the most recent rating and a high safety rating.  Ideally, choose a meter that is CAT-IV 600V rated; this means that you can safely use the meter on circuits up to 600 volts RMS. To find out more on safety and how the latest power monitors have been designed to enhance worker safety read these papers on NFPA 70E and Power Monitoring Safety.

Successful Monitoring

Performing a power study with a power monitor involves several steps; connecting, setup, downloading data, analyzing and producing a final report. If the connections or the setup are wrong then the study is worthless.  The more intelligent meters have built-in software to guide the user by alerting them to connection errors, and excellent PC software to analyze the data and generate a report with an easy-to-use wizard approach. PowerSight meters are designed to guide the user through the entire process, step-by-step, to ensure success. This article describes the Power Monitoring Process.