A Checkup for the Back-up Power Infrastructure of Medical Laboratories
In light of recent disasters, hopitals upgrade their backup power systems
JCAHO said, “Health-care facilities are highly dependent on reliable sources of electrical power. Therefore, electric power is a mission-critical resource. Each
Figure 1. Dirty and distorted power wreaks havoc with sensitive lab equipment.
health-care facility must assess the risk of electrical power failure—at various degrees of magnitude and impact severity—and make plans to deal with such an emergency.” They further said, “A power failure can range in magnitude and impact from a relatively modest curtailment of power caused by a local power disruption to a catastrophic regional blackout caused by a violent storm or terrorist attack.”
JCAHO states that meeting NFPA codes and standards are only a start and has issued a new standard, EC.7.40, in addition to existing standards EC.7.10 and EC.7.20. The JCAHO assigns the responsibility for enacting the new standards with each facilities management and engineering staff. New changes and suggestions for proactively assessing a facility’s vulnerabilities include:
• Testing backup generators every 36 months for four hours. This is in addition to the existing requirement to test the generators every month for 30 minutes.
• Meeting with the local power utility to assess the reliability of the existing power system. Many utilities are operating at near capacity or have outdated equipment.
• Responding to facility brownouts and blackouts as symptoms of marginal utility power.
• Fully testing the entire emergency power system against the requirements of NFPA 110.
• When planning for new construction, locating multiple generators in differing locations, e.g., the basement and the roof.
• Assessing the need for additional redundancy through portable, truck-mounted generators and developing procedures to isolate generators from problem areas and to tie in supplemental equipment.
• Developing contingency plans that address continued availability of health information technology (HIT) systems.
Figure 2. On-line double-conversion diagram.
But are backup generators enough?
ON-SITE POWER GENERATION
Though on-site generators can provide long-term back-up power, during a power outage there is a lag of several seconds while the generator(s) turns on. This break in power is often disruptive to many types of hospital and lab equipment. Sensitive instruments, such as DNA analyzers, GC/MS, LC/MS, centrifuges, computers, data storage systems, and hundreds of other pieces of microprocessor-based equipment.
After Katrina, FEMA issued new guidelines for power backup in hospitals, police stations, and fire departments. These new standards are more stringent and were derived from the lessons learned in Katrina. Lab instruments all depend on a constant flow of clean, regulated ac power. To prevent problems, the incorporation of on-line uninterruptible power supply systems (UPS) on power sensitive, key equipment is an essential extra layer of protection. The on-line UPS provides no-break battery backup during generator startup. It regenerates clean, tightly regulated power when operating from utility or generator sources, removing unwanted frequency drift, voltage transients and harmonics. Unfortunately, not all UPS products available are of the on-line design and as such cannot provide the same high levels of power protections.
THE RIGHT POWER PROTECTION
The Institute of Electrical & Electronic Engineers (IEEE) defines UPS topologies in the following categories: “off-line,” “line-interactive” (hybrid), and dual-conversion on-line.
The difference between these UPS topologies is often not clearly understood. About 90 percent of the UPS on the market today are actually off-line or line-interactive designs. These battery backup units are low cost and designed to address the basic backup needs of home PCs and office desktop computers. Utility or generator power is fed directly through these designs until power is lost, at which time they switch over to a battery-powered inverter. The switchover is often not very smooth, creating a 10 to 20 millisecond power drop out, which can be very disruptive to sensitive equipment. Further, ac output created during battery operation is not a true sine wave. Often referred to as quasi-sine wave or modified sine wave power, this power can disrupt the operation of, and even damage sensitive laboratory and hospital equipment (see figure 1).
The line-interactive ups or “smart UPS” is the same basic design as the off-line, except it incorporates a boost/buck transformer that senses the incoming utility or generator voltage and automatically switches transformer taps in an attempt to regulate the UPS’s output voltage. This is often referred to as an AVR feature. At best, the AVR provides a crude method of output voltage regulation, typically ±8 to 12 percent. To make things worse, the UPS has to switch to battery mode every time the AVR has to switch transformer taps, adding voltage dropouts to the mix. This is actually a band-aid approach and often causes more problems if used with laboratory instruments. The AVR can also result in a greatly reduced battery life in locations with constantly changing utility voltages due to over-cycling of the batteries.
The dual-conversion on-line UPS regenerates totally new sine wave power both in utility and battery backup modes. It converts the incoming ac power to filtered and regulated direct current (dc). This dc power is continuously supplied to a high-quality, PWM inverter that regenerates clean, new tightly regulated ac power (see figure 2). This active approach ensures superior ±2 percent output voltage regulation and provides the highest level of power conditioning demanded by sensitive laboratory and hospital equipment.
Figure 3. Clean waveform after being regenerated by a Falcon On-line UPS. Noise, voltage drop-outs, and distortion have been completely removed. Only pure sinewave power is being supplied.
Additionally, in contrast to off-line and line-interactive UPS designs, the on-line UPS only uses battery power when utility power is not present. Therefore, battery life is typically much longer. The on-line UPS has no disruptive switchover drop when utility power is lost or restored. Most new on-line UPS also provide input power factor correction. This greatly reduces harmonics that may adversely affect building wiring and other equipment operating inside a lab.
Finally, another feature available with some on-line UPS is galvanic isolation. This eliminates neutral-to-ground and common mode noise paths, as well as ground loops by electrically isolating the instrument to increase accuracy and data communications reliability.
On-line UPS are available in small portable form factors in sizes ranging from 1 to 40-kVA that may be used to protect individual or multiple pieces of equipment distributed throughout the facility. They are also available in large permanently mounted form factors in sizes from 40 kVA to several hundred kVA that are capable of powering the entire facility. One must be cautious as installing one large on-line UPS to protect the entire facility may still leave power sensitive equipment unprotected from localized power pollution problems. Large motors, pumps, photo copiers, x-ray, MRI, and equipment having a high intermittent power demand located throughout the facility are often a source of localized power pollution. As the sensitive equipment is connected to the output of the large centralized UPS, the disruptive equipment can cause voltage sags and swells in addition to high voltage transients (see figure 3).
In addition to superior power protection, due to its design, the on-line UPS may be incorporated into disaster planning in ways that are not apparent. Many on-line UPS models have dc start functions and an inverter rated for continuous or sustained duty, and so they may be packaged on a portable cart with large extended battery banks to provide 20 minutes to several hours of emergency ac power for essential equipment in the event utility and generator power is not available.
Many hospital and emergency medical facilities are backing up their medical and billing data in real-time, either offsite over the internet or through dedicated data lines. It is essential in any disaster plan that adequate backup time be provided to ensure the data transfer is complete successfully. Computers, servers, networks, routers, and data line equipment all have a reliable backup source during this critical time. Multiple on-line UPS units with enough battery backup time to power every piece of equipment in the system is mandatory.
On every laboratory, accurate results are mandatory. Nowhere is this more true than in law enforcement forensics DNA testing. A DNA sample may be limited to a onetime attempt at obtaining accurate results. The sequencing can take a substantial amount of time, and the sequencing equipment must operate flawlessly during processing. The disaster in this lab may be caused by a momentary loss of change in utility voltage and result in the bad guy being put back on the streets.
The integrity and security of patient records and emails is mandated by law and is only as secure as a facility’s computers, servers, networks, and offsite backup systems. All these systems depend on a continuous, clean, and redundant power sources. Meeting these mandates will require more than provisioning multiple power sources but will also include an assessment of the local telephone company’s and ISP’s ability to continue to support reliable service during disaster scenarios. As a hospital in New Orleans found out, there was no substitute for a standard POTS line powered by the telephone company’s backup batteries. When all of their T1 and Fiber lines went down, the POTS line and a laptop with an acoustic modem saved the day.
Reprints of this article are available by contacting Jill DeVries at firstname.lastname@example.org or at 248-244-1726.