The Power of Reliable ResultsGood power quality is essential to achieving reliable laboratory test results.by Michael Stout, V.P. of Engineering, Falcon Electric, Inc.
At a Glance
• A power quality audit should be part of a test data acceptance program.
• Power audits must include every instrument, computer and device that will be connected.
• Lab disaster plans may require power reliability, according to new FEMA backup power guidelines.
• Backup generators and UPS should be specified for the connected equipment. | Fifty years ago, scientists and technicians like today strived to achieve the highest level of accuracy and repeatability. But best laboratory practices relied upon good scientific method, which the chief scientist usually defined, and tests now considered simple were complicated and time consuming, considering the rudimentary equipment used. Thus, the accuracy of test results varied from technician to technician or lab to lab.
Implementation of laboratory quality standards, such as ISO 9001:2008 and ISO 17025:2005, and innovative microprocessor-based technology led to a higher level of testing accuracy and repeatability in labs throughout the world.
These high-tech designs, however, created a new issue that most quality standards do not address—power quality, which affects the accuracy and repeatability of most laboratory equipment. Power quality is also important when considering a lab’s data reliability, record keeping and storage mandates.
Products News
Power quality audits
One of the world’s premier product safety and testing companies recognized the problem with dirty, unregulated power and implemented a power quality audit as part of their test data acceptance program. According to this F500 company, “environmental conditions have a direct impact on test results, and accuracy and consistency are affected by laboratory conditions.” The company’s audit is conducted both inside their test labs and at their customers’ labs prior to accepting product qualification test data for clinical lab equipment.
What should a good Power Quality and Reliability Audit Plan include? The IEEE Standard 1159-1995, IEEE Recommended Practice for Monitoring Electric Power Quality, is a good place to start. It covers power quality phenomena, monitoring objectives, AC voltage measurements, AC current measurements, voltage and current considerations, monitoring instruments, application techniques, safety, and power monitoring result interpretation, as well as other topics.
A full audit of the power requirements must be conducted, including every instrument, computer and device that will be connected. Proper electrical circuit and outlet requirements can then be determined.
Manufacturers are required to indicate the steady-state current or power demand on the equipment’s nameplate label. When first turned on, some instruments may demand several times the indicated steady-state power. This is referred to as “inrush current.” If the utility circuit is not dedicated, or the generator or uninterruptible power supply (UPS) powering these pieces of equipment is not properly oversized, equipment reliability and test results could be affected throughout the lab.
Some equipment may actually cause other types of power problems, such as harmonic distortion or voltage sags, and interfere with other instruments or computers in the same lab. The manufacturer should always be contacted to determine inrush current or other special power requirements before installation.
Reliability backup
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| Figure (a) The output of a standard generator source shows a distorted, dirty sinewave, which can affect the accuracy and repeatability of equipment. (b) A high-quality UPS converts dirty power into regulated DC power, which is used to regenerate clean, precision-regulated AC power. |
 | Local environmental issues that may affect a facility’s power quality and reliability must also be included the audit, i.e. severe lightning, ice storms, floods, utility reliability, building age and wiring conditions. These issues must be considered and addressed if the lab work is of a critical nature.
A hospital in New Orleans, for example, installed a mandated backup generator years before hurricane Katrina. Unfortunately, the generator was installed in the basement, and flood waters immediately rendered it inoperable. Since that lesson, FEMA has issued new backup power guidelines for installations in hospitals, police stations and fire departments. Labs may fall under these new guidelines, and power reliability may be required in a lab’s disaster plan.
Backup generators and UPS requirements must also be assessed. A high-quality, double-conversion, online topology UPS not only provides the necessary battery backup for critical equipment but is also a power quality problem solver. This type of unit takes the dirtiest incoming utility or generator AC power, converts it to a regulated DC power, and uses the DC power to regenerate clean, precision-regulated AC power.
The UPS acts like a power firewall between the building’s power and sensitive equipment, providing protection against both utility and localized power problems created by other equipment. The online UPS can also be configured with extended battery banks to provide several hours of battery backup. This could be invaluable when keeping key laboratory equipment powered long enough to ensure tests are properly complete, even in the event of a long-term power outage.
The UPS buyer must beware: Not all UPS products designated for use with computers feature the online design and thus do not provide adequate protection. Those UPS units are designated as off-line or line-interactive UPS designs, which pass dirty utility or generator power directly to connected equipment. Many are not compatible with generators at all.
Some instruments take such sensitive measurements that they are adversely affected by stray currents flowing on power grounds. In this situation, the equipment must have galvanic isolation installed directly ahead of the power plug. This electrically isolates the equipment from the utility power, breaking the path of the unwanted current flow. When needed, an online UPS with internal galvanic isolation may be the simple solution.
Conclusion
The power quality and reliability audit is only as good as those conducting it. A reputable power consulting firm should be contracted to assist with the initial planning and perform the first audit. They will also be able to determine the best course of action to resolve a problem.
Follow up audits should be conducted as part of your lab’s ISO9001:2008 audit schedule. This will ensure new equipment and facility changes are regularly reviewed.
For more information, contact Falcon Electric at www.falconups.com or call 800-842-6940.
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