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Quality Power, Not Just Power, Should be the Goal

February 11, 2016 By Carl Weinschenk

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A priority for energy managers, of course, is to make sure that electricity keeps flowing. The next level of concern is to find the desired mix of low cost and renewable resources.

A very important factor that may ride a bit under the radar is the need for quality. Having a power supply is one thing; having one that is conditioned to be reliable, constant and safe for sensitive electronic gear is another. In other words, facility managers – especially those working in healthcare facilities and similar mission-critical facilities — should think a lot about quality.

Debra Vieira, a senior electrical engineer at CH2M, wrote at Consulting-Specifying Engineer that there is some haziness in the definition of quality power. Most simply, quality power is synonymous with “purely sinusoidal” waveforms. She immediately adds, however, that some deviation from the perfect repetition of the waveform is permissible without losing the right to use the “quality” label.

Her conclusion is more or less that “quality” power is in the eye of the beholder. Do harmonics and intermittent transients, for instance, signify poor power quality, or are some of these permissible? There is no yes or no answer: “Technically, there is no single accepted definition” of quality power, she writes.

Those nuances aside, there is no question that the quality of the power used is important to facilities managers and building owners:

xxxWe are interested in power quality because of its economic impact. An increasing majority of industrial, commercial, and service businesses are sensitive to power quality problems because they affect a company’s ability to compete in a global economy. Businesses that depend on high quality power, such as information technology or the continuous process industry with its programmable logic controllers, distributed control systems, industrial computers, human-machine interfaces, variable frequency drives (VFDs), motion controllers, and sensors, can suffer huge financial losses along with loss of productivity and competitiveness when power disturbances occur.

A post at The Electrical-Engineering Portal offers a practical description of quality power and the issues around it. First, the definition:

The term ‘good power quality’ can be used to describe a power supply that is always available, always within voltage and frequency tolerances, and has a pure noise-free sinusoidal wave shape. ‘Poor power quality’ describes any supply that deviates from this ideal; whether or not the deviation is important depends on the purpose of the installation, the design of the equipment and the design of the installation.

Problems dragging supplies from quality to non-quality status can occur in the supply and distribution chain or within the facility. Problems in one area can cascade into the other, so the distinction can be less than muddled.

The provides a bit of detail on the main problems in each of these realms. Supply system problems are supply interruptions (outages of more than one minute); transient interruptions (complete loss of power for less than one minute), transients (quick high voltage pulses); under and over voltages; voltage dips and surges; voltage imbalances; flicker and harmonic distortions. Installation and load-related problems include harmonic currents from non-linear loads; “earth leakage currents” and voltage dips and transients.

It may be that the emergence of big data and the Internet of Things will add new dimensions to the art and science of protecting the quality of a power supply. Writing this week at Buildings.com, ASCO Power Technologies’ Bhavesh Patel discussed the importance of continual “sophisticated, proactive monitoring of power.”

Patel enumerates reasons that deep monitoring and analysis is important: They lead to quick recovery if there is a problem, provide “enhanced analytics” that that create an historical baseline against which current performance is measured and helps fulfill a number of compliance requirements. He mentions three from the National Fire Protection Association: NFPA 70, NFPA 99 and NFPA 110. Softer benefits, such as energy cost reduction and tenant satisfaction, also are gained, Patel wrote.

Patel doesn’t mention big data and the IoT directly, but these sophisticated new platforms clearly are capable of playing a key role in protecting power quality.

These new tools no doubt will work in concert with those that exist. Vanya Ignatova, a power quality marketing expert at Schneider Electric, looks at the equipment options that address common challenges to the quality of power in an electrical system. Transients, not surprisingly, are addressed with transient voltage surge suppressors. Voltage sags and interruptions in the short term are best neutralized with uninterruptible power supplies and other energy storage solutions. In the longer term, backup/self-generation equipment is necessary. Harmonics can be controlled with active filters and power factor issues require the installation of capacitors, she writes.

There is an energy efficiency angle to power quality as well. “The idea is that along with the benefits of reliability and asset management and capacity  management and maintenance and diagnostic functions you also get a whole package of energy management functions that you can use to monitor your electrical network for power quality issues that may be energy wasters,” said Lee Featherstone, Schneider Electric’s Business Development Director of Eco Buildings. “That would touch on things like power factor, harmonic distortion and load balancing issues.”

It seems that quality power is more an aspiration than a definitive level of performance. There is a lot that can go wrong with a facilities’ power supply, both before or after arrives. Constant surveillance is key. The good news is that the capability to do this is growing. Energy managers should take advantage.

One comment on “Quality Power, Not Just Power, Should be the Goal

  1. It should be noted that many energy saving devices (VFDs; LED lighting, etc) generate harmonics which degrade the quality of the supply voltage. Standard practice in many places is to monitor the Quality of supply before and after the installation of such devices to ensure the distortion does not exceed the IEEE/IEC standards. It should also be noted, there are no International standards for acceptable levels or frequency of occurrence of voltage sags (dips) and very few if any manufacturers of sensitive equipment who specify maximum amplitude of transients line to neutral or neutral to ground.

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