09/01/2007

Considerations for Power-Quality Monitoring

Identify the root cause and quantify the solution required to fix power-system problems

 

 

The Value of Historical Data

There are many factors to consider when performing power-quality monitoring. Most of these considerations depend on the nature of the individual problem being investigated. 

Evaluating power-system parameters (voltage, current, power, PF, harmonics) over time can give an indication of excessive conditions that may exist. The graphic above shows the statistical mean and typical max/min ranges for the data shown. It also gives an indication of the quality of power over the past 10 minutes and 24 hours. These "thermometers" are a quick summary of the conditions of a building, indicating if an unusual power-quality condition has occurred recently.

Power-quality monitoring has become increasingly common as the capabilities of commercially available monitoring systems have increased and costs have fallen. Power-quality engineers have used various power-monitoring tools for many years. In recent years, several trends have converged, resulting in the wide application of power-monitoring systems beyond power quality or power-management specialists.

Today, power monitors can track virtually any electrical parameter of interest. With all of the monitoring options available, a number of questions need to be asked: "What should we monitor?" "Which type of power-monitoring system should be selected: permanent or portable?" "What does my power-monitoring system need to measure, how fast does it need to sample, and how accurate does it need to be?"

When the lights flicker in a building, the first question a facility manager typically asks is: "What happened?" Unfortunately, in most cases, he/she does not know. The facility manager knows that the power went out momentarily - or did it? Characterizing the event by the voltage magnitude and duration, and evaluating the current coincidentally, helps identify the root cause and quantify the solution required to fix the problem.

If the company is adversely affected by such power-system events, corrective action may be warranted. But, without knowing exactly what happened (not only during this event, but over a period of time), the company probably doesn't have enough information to make a well-informed decision about which corrective action to pursue. For example, the company might invest in an uninterruptible power supply (UPS), which can ride through outages and interruptions for minutes, but the problem might actually have to do with transients (short-term, high over-voltage conditions).

Basic considerations when selecting a monitoring system and analyzing power-quality issues include:

  • Monitoring at the incoming service (from the utility) and downstream (near critical loads) to help distinguish where problems may have originated.
  • Monitoring for a complete business cycle at a time when the problem is likely to occur (typically for a 1-week minimum).
  • High sampling speeds, preferably 10 times the frequency of interest, to characterize fast transients caused by utility switching events or lightning. Often, transients occur, but the monitoring equipment may not sample fast enough to capture the event.

While portable monitors are more suitable for troubleshooting measurements, permanent monitors offer several important benefits: They're always monitoring, they're proactive and can help notify users of problems in advance, and they capture power quantities useful for energy-saving opportunities. Many companies track energy usage, peak demand, power factor, etc. in order to minimize their power bills. They may also compare their measurements with their power bills to make sure there isn't a discrepancy.

Remote communications with power-monitoring systems are essential to log data from such systems and communicate with users (paging the facility manager following an event, for example). Remote access via the Web is the preferred choice so that facility managers can access data remotely at any time and, secondly, so that experts can support the analysis from virtually anywhere in the world.

Dan Carnovale is power quality solutions manager at Cleveland-based Eaton Corp. (www.eaton.com).

 

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Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.

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Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
CLICK HERE to find out how.


Mitsubishi Electric’s H2i R2-Series heat pumps provide 100% heating capacity down to 0° F and simultaneous heating and cooling down to -4° F delivering year-round comfort, regardless of climate zone.

Connectrac wireways offer discrete power and technology connectivity in open interior spaces of all kinds; affordably, quickly and with long-term flexibility.



When choosing a metal-clad building for your next construction project, consider Morton Buildings, Inc., and their designBUILD team, we’ll make your dream a reality.

Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.

Wood construction is both cost and energy efficient. Check out Morton Buildings and our designBUILD team online today to discover all the benefits of post-frame construction.

We Can Help You Reduce Energy by 30%

Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
CLICK HERE to find out how.


Mitsubishi Electric’s H2i R2-Series heat pumps provide 100% heating capacity down to 0° F and simultaneous heating and cooling down to -4° F delivering year-round comfort, regardless of climate zone.

 
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