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The Power to Produce.

Proactive planning for power quality and reliability

The need for power quality in commercial facilities has grown computer to comprehensive server networks from an electric drip coffee pot to sophisticated video conferencing equipment, it's a given that commercial buildings need to be well-wired to provided constant, reliable power for today's electronic world.

And in the tenants' minds, building owners and facilities managers take the immediate blame when the lights dim and the computer system crashes.

"Tenants are rapidly moving toward a widespread expectation that good power quality and reliability are a given," says Larry Vanderburgh, director of training and instruction at BOMI Institute, Arnold, MD. "Everyone knows computer systems are part of office life and work, and that computers need quality power and reliability. They naturally extend this logic to building owners and expect them to provide reliable power to keep their computer systems and networks running."

It's no wonder why commercial landlords are moving in this direction. Once left in the realm of electrical engineers, such terms as uninterruptible power supplies, surge arrestors, and harmonics are rolling from the tongues of owners and managers. Power quality has come to the forefront of building management, and most facilities professionals strive to ensure as reliable a power network as they can muster.

To achieve any sense of power quality, you must take your building's system over and above what current electrical codes require, experts say.

"Building codes usually deal with the minimums driven by safety," notes Brooke Stauffer, director of codes and standards for the National Electrical Contractors Association (NECA), Bethesda, MD. "The National Electric Code is a minimum safety code. It designs a system that is safe but that might not be the highest-performing electrical system. Building owners need to think about what additional level of quality or reliability needs to be built in beyond the basic code requirements."

Power quality means power without spikes or wide voltage swings, minimal outages, no brownouts, and no harmonic distortion. A power supplier can assure all but the last one, according to Vander-burgh. But harmonic distortion -- waveform fluctuations caused by the power supplies of certain electrical or electronic equipment -- is a function of a building's occupants.

Although a perfect power system with 100-percent reliability cannot be obtained realistically, today's technology provides solutions that can get facilities near this lofty goal.

There are distinctions between redundant/backup, emergency, standby/fast recovery, continuous, and clean power But to tenants, these terms mean the same thing: ways to keep their electricity available and operational with no service disruptions.

The first consideration is ensuring building has sufficient power to satisfy the electrical requirements for the technology and electrical loads it supports.

You need to ensure that this service not only is appropriate for current and projected needs but also if there is sufficient physical breaker space in the facility's panels to handle increased number of circuits. Failure to do so could result in electrical overloads.

Most electrical problems are "glitches" -- small sags or surges or other relatively minor fluctuations that do not cause outages but can affect the performance of electronic equipment. Online uninterruptible power systems, such as surge protection, smooth out those glitches and keep things running smoothly.

In the case of outages - brownouts or blackouts - more sophisticated measures generally are needed. "If power outages cannot be tolerated, a standby power system, such as a generator, can be installed," says Neal Boothe, an engineer with GRG Vanderweil Engineers Inc. in Maitland, FL. "If outages due to maintenance of the generator cannot be tolerated, parallel generators can be provided. If momentary outages between the loss of utility power and startup of the generator cannot be tolerated, an uninterruptible power source (UPS) may be added. A UPS system may even be double-ended and/or paralleled to provide continuous power while another UPS is down for maintenance."

You can add layer upon layer of sophistication to your facility's power reliability system if you choose. But, as Boothe cautions, with each layer of added protection comes another layer of costs.

"A facility owner must weigh his power reliability concerns against his bottom line," he says. "The facility's risk of power failures and outages should be a driving force in evaluating the level of electrical reliability."

Simply put, there is no right answer to how much redundancy is enough when it comes to reliable power.

Subodh A. Kumar, an IFMA fellow and president of Chartered Facility Management Group Inc., Pasadena, CA, suggests working with a qualified consultant with expertise in power quality issues for the specific type of facility in question.

"Lately we've heard a lot about N+1 and N+2 facilities requiring multiple levels of redundancy for facilities that are expected to operate 24 hours, seven days a week," he says. "A business case analysis [should be used] to determine the cost-benefit ratio of such investments."

Gregory Massey, PE, a Kansas City-based electrical engineer who has experience in both public and commercial facilities, says using engineering judgment in making fundamental design decisions, such as installing separate grounding conductors to supplement metallic raceways, is the first step in ensuring good power quality.

Many high-rise buildings, for example, have two incoming electrical lines. When two or more electrical lines are in-phase, they can be designed to supply the load at the same time. This is commonly referred to as a "spot network." If one line is lost, the other line(s) seamlessly pick up the load without perceptible loss of power. And it works.

"An 18-story office building in Kansas City, for example, has four utility feeders networked together and uses UPS systems for some of its critical clients," Massey says. "That building blew a transformer, and nobody within the building knew it happened. The utility company came knocking on the door four days later, saying it traced a dead fault to the building. When that transformer blew, the other three lines picked up the load, and things operated as usual. The power to that building has never been interrupted. It would take a complete blackout in downtown Kansas City to knock that building off-line."

The benefits of uninterruptible and standby power lie in helping building owners manage their risks. This risk may involve the loss of crucial data, such as a data center; the loss of revenue and production, such as a manufacturing environment; or a threat to public and/or patient safety, such as healthcare facilities. Facilities professionals must manage the risk of power outages vs. the cost of providing the level of standby and/or uninterruptible power necessary. It often comes down to weighing the benefits of increasing the electrical system's reliability against the cost of the increased systems and making an informed decision based on the evidence.

Because most facilities professionals are generalists and expertise in electrical and power issues tends not to be a core competency, retaining an experienced power quality consultant can help facilities professionals ensure that a building's systems are optimally designed and specified. A business impact analysis of power quality can clarify exactly what tenant needs the building must fulfill and guide development of the proper power reliability system.

"The facility's risk of power failures and outages should be a driving force in evaluating the reasonable level of electrical reliability," says Vanderweil Engineers' Boothe. "There is no one right answer to this question. The electrical system that may be cost prohibitive and excessive for one owner may not provide the protection another owner desperately needs."

Robin Suttell, based in Cleveland, is a frequent contributing editor to Buildings and BI-Buildings Interiors magazines.

There's No Upside to Downtime

Power quality issues arise from a number of sources, both internal and external, and the factors are never quite the same from day to day.

"Power fluctuation is caused by various pieces of equipment going on and off, bringing spikes into the supply," notes Subodh A. Kumar, an IFMA fellow and president of Chartered Facility Management Group Inc., Pasadena, CA. "The same situation can occur from others within the building or even the region, as well as from the quality of the supply grid and its capacity."

External sources include transient voltages, such as lightning strikes, and voltage and/or frequency sags or surges from the electrical power company source. Internal sources of poor power quality often include momentary in-rushes from larger equipment causing voltage and frequency dips in the electrical distribution system integral to a facility. Culprits include large motor loads, large distribution transformers, and, in the case of healthcare facilities, radiology equipment start-up.

That's not to say smaller, more mundane electronics don't have an impact on a building's electrical load.

Greg Massey, PE, an electrical engineer based in Kansas City, says while an electrical load profile is in constant transition, it does go through a predictable cycle each day.

"Loads build in the morning as the doors open for business and employees turn on computers, lights, radios, fans, coffee pots, displays, microwave ovens, and other machinery," Massey says. "Loads begin to taper off in the evening as employees leave work or when there is a shift change. Typically, minimal lighting and environmental loads exist overnight or whenever the business closes for the day."

Likewise, these loads also exhibit a seasonal cycle. Depending on the part of the country and the type of heating and air-conditioning used, the electrical loads will be higher depending on the weather, peaking either in the summer or in the winter. Because of this cyclical nature, it takes time to determine the root cause of intermittent power quality problems. Typically, an existing electrical system must be evaluated over time.

"An owner or facilities manager can spend valuable time pursuing a quick fix when the system should be evaluated over time," Massey says. "Many times, the approach to poor power quality is to treat symptoms while neglecting to look for the cause of the problem. It's analogous to taking two aspirin and calling the doctor in the morning."

In most cases, Massey says, the quick fix might appear to solve the problem, but because many symptoms of poor power quality take a long time to appear, the fast solution simply buys time by marginally improving the operating conditions of selected equipment.

"In other words, it takes longer for equipment to fail," Massey says.

Treating symptoms with a Band-Aid approach also can result in solving the wrong problem with overly expensive equipment replacements that aren't really necessary.

For example, many power quality problems are manifested in transformers that overheat.

Transformers can overheat as a result of such power quality-related issues as over-voltage, current harmonics, voltage harmonics, and resonance, Massey says. Transformers also can overheat from insufficient ventilation, high ambient temperature, overloading, and single phasing. Whether a problem is related to the transformer itself or simply symptoms of a power quality issue is something that needs to be determined over time.

"Replacing a failed general purpose dry-type transformer with a K-rated transformer capable of supplying harmonic-generating loads is a very expensive solution if all that is required is routine maintenance to clean transformer vents," Massey says.

Power quality experts also caution facilities professionals of the importance of realizing that their power equipment offers no more protection than the weakest link in their system.

Electrical experts at GRG Vanderweil Engineers Inc., Maitland, FL, recently assisted a client with an uninterruptible power source (UPS) for an existing data center power supply. The client had been experiencing downtime for a non-related issue, and Vanderweil engineers recommended use of a battery monitoring system to ensure uninterruptible power availability.

Upon completing the installation of this system, the facility discovered two batteries had failed within its UPS system.

"The failure of any additional batteries could have affected the ability of the UPS to supply uninterruptible power," notes Vanderweil engineer Neal Boothe. "This client would not have learned of this failure until the moment of a power outage when UPS power was expected but unavailable."

A proper electrical distribution system is made of components that are carefully selected and balanced to function as a system. Any modifications to such a system must be made with diligent care. And, consideration must be given to any effects resulting from system changes.

"It's important to fully understand and correct the true causes of poor power quality, using symptoms as clues," Massey says. "Expanding the medical analogy, we can treat symptoms with quick fixes all day, but there will be side effects from drug interactions and the pharmacy bill is going to be expensive."

In Application

Fort Bragg, one of the largest army bases in the United States, faced an enormous challenge: The 160,000-acre base was consuming peak electricity at an alarming rate.

Located near Fayetteville, NC, Fort Bragg receives its electricity from Carolina Power & Light and has contracted for a maximum demand of 78 megawatts that can be imported without penalty. To limit this ever-rising demand and avoid penalty charges from CP&L during times of peak energy use, Fort Bragg deployed an aggressive plan using controls and software from ENCORP Inc.

In June 1999, ENCORP and Fort Bragg retrofitted 11 standby generators located at various facilities around the base that supply up to 3.85 megawatts of power. A common electrical-distribution system serves the facilities.

The ENCORP equipment installed at each generator allows the generators to run in parallel with each other as well as be interconnected with the utility grid. ENCORP's entelligent[R]-VMM (Virtual Maintenance Monitor) software manages the 11 enpower[TM]-GPC (Generator Power Control) units controlling the generators, which in turn are connected through a LONWORKS[R] communication network.

Operators for each generator instantaneously can access generator status, maintenance requirements, and alarm information via the single central Dispatch Workstation running ENCORP's VMM software.

The results? Fort Bragg's peak demand already has dropped by 3.85 megawatts due to the peak-shaving conversion, and electricity costs will continue to decrease significantly. In addition, Fort Bragg will recognize improved performance of its ENCORP-enhanced generators. Regularly exercising engines and generators under load improves their reliability and availability in the event of a grid outage. entelligent-VMM software enpower-GPC units by ENCORP Inc., Windsor, CO. Circle 201.
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Author:Suttell, Robin
Publication:Buildings
Geographic Code:1USA
Date:Oct 1, 2001
Words:2353
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