Staying in Power

Power-quality experts highlight benefits, challenges and new advances in power monitoring and conditioning equipment

06/01/2001


In the wake of West Coast power outages and with increased concerns about power quality, experts from around the country come together in this month's M/E roundtable to discuss strategies for better power metering, monitoring and conditioning.

CONSULTING-SPECIFYING ENGINEER (CSE): What are the biggest benefits provided by power metering, monitoring and conditioning equipment?

MAYZENBERG: Power-metering and -monitoring equipment helps the end-user understand and analyze a facility's power consumption, peak demand and power quality—for both utility power and distributed power. Power-conditioning devices and equipment improve power quality and increase the reliability of electrical systems by fighting transients, electrical noise, harmonics and long-term undervoltages and overvoltages.

BUTT: Information-technology sector growth has meant an explosion in "critical" facilities; manufacturing requires more and more complex systems: Both these trends place greater demands on the design engineer. Downtime costs can run into the millions of dollars per hour—or even millions of dollars per minute—and end-users demand answers whenever system disturbances occur.

GUTH: The biggest benefit of power-metering and -monitoring equipment is that it puts users in a proactive situation by increasing their knowledge and giving them the information they need to increase the reliability of their systems. Today's meters and power monitors have the capability to capture events, provide historical trending data and even provide control functions. This information can be used to help reduce energy demand during peak power-consumption periods, as well as assist in analyzing harmonic-distortion levels needed to determine and implement corrective measures.

COLONNA: Long-term metering provides facility owners with a "map" of load changes, allowing the owner to track daily, weekly and seasonal variations, as well as discern long-term trends. This capability aids in planning for maintenance outages, increasing loads and capital expenditures for system upgrades and improvements. In addition, owner metering gives users a comparison base for determining how reasonable utility billing is, and for identifying money-saving opportunities on electric bills.

Continued monitoring can detect a deterioration in power quality before equipment problems arise. Maintenance personnel sometimes blame power quality for unexplained equipment failures, only to reverse their stance and really look for the source of the problem when confronted with data demonstrating historically good power quality. Tightening up those specs

CSE: What is involved in specifying the most effective equipment for a project? GUTH: Specifying power-metering, -monitoring and -conditioning equipment involves addressing the following questions:

  • What information is important? The users need to know specifically what information is needed from the device or how the information can be derived from the data retrieved.

  • How does the information need to be gathered? Can the measurement be recorded by hand, or does information need to be logged continuously and time stamped?

  • Where is the information needed from the electrical system? Is electrical information important at one location or several?

  • Why is the information important to a facility? Is it for compliance with guidelines required by the connecting utility, increased reliability, internal facility energy management for reducing energy costs or possibly a combination of reasons?

Answering these questions helps to provide the parameters needed to specify a particular meter.

COLONNA: The first step is to identify and quantify the existing conditions. Next, define the function and performance required. What is the objective of metering, monitoring or power conditioning? What are the accuracy parameters for metering? What are the power-quality tolerances for the supplied loads? How critical is continued operation of the load? What are the redundancy and maintenance requirements?

KOLOWITZ: Determine first if the system to be protected and monitored is critical. Evaluate the site history of power outages and the cost per hour of downtime against the cost of protective equipment. Each load creating transients and harmonics should also be evaluated. Accurately determine the clean power requirements of every piece of electrical equipment involved in the project. Determine the utility requirements with regard to power quality. Next, examine the effectiveness of each type of power conditioner. Finally, assess the cost effectiveness of each technology.

BUTT : Each facility's electrical distribution system is unique. It is important that the owner's objectives for monitoring and conditioning—together with the project budget—are clearly understood by the engineer. It's up to the engineer to make sure the client understands the benefits of the proposed system.

CSE: In what capacity do you see power-conditioning equipment most commonly being used? Is it critical for a facility?

COLONNA: In U.S. facilities, power conditioning is generally provided for critical computer and communications equipment, although we now specify at least transient-voltage surge suppressors (TVSS) for almost all facilities. Owners are tending to define more and more of their equipment as critical. The more critical the equipment, the more extensive and expensive the power-conditioning becomes.

In developing areas of the world, where power availability and quality varies widely, TVSS, voltage regulators and prime or standby generators are often provided to serve an owner's entire facility, with uninterruptible-power supply (UPS) systems for critical computer and communications loads. In such locations, the local utility supply is so variable that power conditioning is essential for maintaining normal daily operations.

MAYZENBERG: The use of power-conditioning equipment is critical for a lot of health-care clients, especially radiation-therapy equipment, R&D equipment, telecommunications, fire alarms and security systems. TVSS is used practically in all facilities for electrical system protection by suppressing large voltage surges and by filtering noise from incoming electrical lines. Shielded isolation transformers provide transient and superior noise attenuation, as well as nearer ground references for sensitive electronic equipment. They also protect power-distribution equipment from the large surges, spikes and harmonics produced by medical equipment.

Power conditioners provide additional protection by combining characteristics of isolation transformers, voltage regulators, filters and surge suppressors. Active and passive harmonic filters, alternating-current line reactors and direct-current link reactors are used to mitigate harmonics produced by variable-frequency drives. Static and rotary UPS systems not only provide the line-sidefiltering and conditioning necessary to assure power quality, but also supply power for a specific length of time after the loss of utility power.

The highest results can be achieved by using UPS systems in combination with emergency generators.

A common mistake may be not reviewing all of the factors affecting the selection of power-conditioning equipment. The major factors are effectiveness of performance, initial and annual operating cost and performance/cost relationship. For example, if performance alone were considered, a UPS would be the choice. If cost alone is considered, the transient-spike suppressor is the choice. If the performance/cost relationship alone is considered, an isolation transformer is the best choice. One must take into account all three parameters and weigh their importance.

BUTT: This equipment can be considered critical if the facility is subject to severe power-system disturbances or harmonic distortion and anomalies, as these affect equipment operation within the facility. Power-quality patrol

CSE: How effectively does power-conditioning equipment deal with power-quality issues?

KOLOWITZ: If properly selected and applied, power-conditioning equipment can be very effective in protecting sensitive electronic equipment, motors, generators, transformers and capacitors. Avoiding breaker tripping and protecting utility and users from harmonics and transients generated in the facility are other effective results of using power-conditioning equipment.

BUTT: When properly applied, maintenance costs decrease, energy use goes down, reliability is improved and operation efficiency increases. For retrofits, owners may have identified the need for the equipment themselves, or they may have come to understand the need through discussions with the engineer. Once the equipment is installed, they easily see the benefits of the power-conditioning equipment because before-and-after data is available. This is not necessarily the case with new installations, and often times, power-conditioning equipment is removed from a project during the first wave of value engineering.

COLONNA: In most cases, failure of this equipment to solve the problem can be traced either to misunderstanding the real problem or misapplying the equipment. For example, poor or improper grounding causes many power-quality problems, which may be hard to identify. Simply adding TVSS to an improperly grounded system will not solve the problems by itself.

CSE: Are there challenges—technical or political—that arise through the process of enabling end-users to access real-time energy usage data? For example, utilities endeavoring to maintain control over this information?

COLONNA: Utilities typically do not want to share their real-time metering signals with a user. However, I have not encountered any reluctance on the part of utilities to having end-users provide their own metering equipment.

BUTT: High-speed, sophisticated power-monitoring systems provide end-users with a great deal of information regarding their facilities' electrical requirements. The 15-minute demand now becomes an instantaneous demand. True power factor, current distortion [and other measures], can all count against the end-user if the utility has access to the information. As the end-user's metering equipment becomes more accurate and provides more detailed information, he or she will have more ammunition to successfully challenge monthly utility bills. This may lead to compromises by both the end-user and the utility.

GUTH: Utilities are welcoming end-user participation. One utility in Utah, for example, has a demand exchange program for users with power consumption over 4 MW. To establish a baseline for demand, they provide a power-profile meter and installation free of charge—approximately a $3,000 value—that allows end-users to access data via the Internet and view their load profiles as recorded in 15-minute intervals. During peak-power periods, the utility notifies end-users in the program to reduce their demand in 500-kVA allotments. If accepted by the user, the power company agrees to pay the user for the power not consumed according to a cents-per-kilowatt-hour basis. The data provided from the meter is free.

MAYZENBERG We have not seen any significant technical or political challenges prohibiting access to this data. Some major healthcare and R&D end-users are limited in their opportunities to move loads—somewhat due to the nature of their work. We believe that real-time pricing is coming; therefore, we have been proactively putting in real-time demand meters or highly recommending them for our clients. Until higher demand or ratchet charges come along—possibly in the form of real-time pricing—there is no economic incentive to implement major proactive strategies. On the horizon

CSE: Are there any significant technological advancements in the works which will improve the quality and operation of power equipment?

GUTH: A new product using flywheel technology is a reliable, cost-effective way to store electricity. Similar products have been around for years, but have not been commercially viable. This flywheel technology may allow some end-users to replace or augment their DC-battery backup UPS systems, in lieu of a flywheel UPS system. Flywheels, in conjunction with a motor-generator, provide clean and sustainable power with load protection from frequency instability, utility failures, voltage spikes, sustained over- and undervoltages, high-frequency noise and harmonic distortions.

A new battery-free UPS system requires 25 percent less floor space, less service, more reliable mechanical energy, nearly unlimited life with no fall-off in performance, half the life-cycle costs of any other battery-based system and 98-percent efficiency. The system is environmentally clean and runs at full performance at temperatures of -4° to 104°F. Facilities such as Web-hosting and telecommunication/data switching centers are prime candidates for this type of UPS system.

KOLOWITZ : An active harmonic-correction system is one technological advancement that we are watching with a high degree of interest. This system provides harmonic control by monitoring a distorted electrical signal, determining the frequency and magnitude of the harmonics that exist in it and then canceling those harmonics with the dynamic injection of opposing current. It also eliminates the potential for resonance by attenuating current harmonics and identifies the harmonic to be cancelled to avoid resonance in the power-distribution system. It also eliminates the current surges caused by electric arc welders or large motors when they start. A new approach, as a result of the active harmonic-correction system, is the hybrid filter. This system is a combination of active and passive filters. The hybrid filter is more effective than either an active or a passive filter alone, but can be rather expensive.

BUTT: The speed of power-monitoring equipment continues to increase. Portable monitors are now available that provide significantly more data than those available five years ago. The Internet is now used to remotely monitor power quality and equipment operation in real time, which will no doubt change the way many companies react to production disturbances.

Power-monitoring equipment with integrated Web servers provide the end-user with immediate access to real-time and historical information. Software updating is also simplified via the Internet or local intranets.



M/E Roundtable Participants

Robert S. Butt, Jr., P.E., project manager, The RMH Group, Inc., Lakewood, Colo.

Edward S. Colonna, P.E., CEM, assistant vice president, Hayes, Seay, Mattern & Mattern, Inc., Roanoke, Va.

Ben Guth, P.E., project electrical engineer, Power Engineers, Inc., Boise, Idaho

Alan Mayzenberg, P.E. , senior electrical engineer and Dan Kolowitz, P.E., senior electrical engineer, Ewing Cole Cherry Brott, Philadelphia

Barbara Horwitz, moderator

Convincing the End-User

Despite the many benefits offered by power meters, monitors and conditioners, electrical engineers sometimes still encounter hesitancy on the part of end-users.

"Some end-users have been reluctant to spend money on power metering and monitoring, especially when payback periods extend more than three years," notes Ben Guth, P.E., a project electrical engineer with Power Engineers, Inc., in Boise, Idaho.

Because end-users often lack time and money, Robert S. Butt, Jr., P.E., a project manager with the RMH Group, Lakewood, Colo., offers the following approach.

"It is often easier for the owner to start small and work up—for example, purchase portable monitors, which are cheaper and easier to operate. After the owner realizes the benefits of this equipment, the move to a more complex, permanently installed system is easier to justify," he says.

Another factor determining how open clients are to utilizing this type of electrical equipment is the end-user's level of education and experience.

"Generally, the more technically knowledgeable an owner is, the more benefit the owner sees," says Edward S. Colonna, P.E., CEM, an assistant vice president for Hayes, Seay, Mattern & Mattern, Inc., Roanoke, Va.

Navigating Pitfalls

While power metering, monitoring and conditioning can do wonders when it comes to increasing energy efficiency, improving power quality and saving money, it might all be for naught if the equipment isn't designed and specified properly.

One of the most common mistakes made, says Robert S. Butt, Jr., P.E, a project manager with the RMH Group, Lakewood, Colo., is specifying a system too complex for the end-user's needs.

"It is important to match the capability of the metering and monitoring equipment to the function of the facility and the technical abilities of the owner," according to Edward S. Colonna, P.E., CEM, an assistant vice president with Hayes, Seay, Mattern & Mattern, Inc., Roanoke, Va.

Another area of concern is how voltage transformers are configured.

"Often voltage transformers for meters are specified in an open delta configuration for three-phase systems, which will not provide all information for all phases," explains Ben Guth, P.E., a project electrical engineer with Power Engineers, Inc., Boise, Idaho. "For example, some information, such as harmonics and power factor, will be missing from one phase."

Guth also stresses the importance of determining whether connecting the power monitoring to a network will ultimately add value to the system.

"For simple systems, networked or remote monitoring may not substantiate the added cost," he says. "But for larger systems with several monitoring points, a networked system will reduce analysis time, increase functionality and provide a more reliable historical data-recording process."



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