The term "high availability" is a buzzword used with increasing regularity to describe the quest for 100% uptime in computer networks, computer-based control systems, and telecommunications operations. Of course, high-quality ac input power is the single most critical element in keeping any of these systems up and running. In fact, power problems are the single largest cause of downtime and data loss in computer-based electronics. According to Contingency Planning Research, power failures and surges cause 45.3% of all data loss; they also cause related hardware damage, reprogramming, and downtime. How bad power affects equipment

Even momentary power disturbances can cause extensive damage. A study by IBM has shown that a typical computer is subjected to more than 120 power disturbances per month with effects ranging from minor keyboard lockups and poor hardware performance to severely damaged equipment and unrecoverable corrupted files. Users can spend countless hours troubleshooting a variety of system problems that can eventually be traced to unseen problems in the power line.

Although contractors can't be expected to troubleshoot symptoms that appear in computer systems, they can make a valuable contribution to the solution by proposing comprehensive power protection plans to customers who require "high availability." With more businesses depending on computer-based operations, the need for power protection has never been greater.

Unfortunately, the commercial utility simply cannot provide the clean, consistent power demanded by sensitive computers. As a result, customers are ultimately responsible for the health and safe operation of their own equipment. The situation is compounded in large commercial settings where nearby industrial equipment, elevators, and copy machines can generate additional electrical noise, sags, and spikes.

A survey by the Gallup organization revealed that more than half of corporations interviewed estimated the cost of downtime at $5000 per hour or greater. At that rate, it doesn't take long to justify power protection.

The best way to assure a continuous, high-quality power flow to critical systems is with an uninterruptible power supply (UPS). These devices are designed to provide backup power and filter out potentially harmful electrical noise, surges, and spikes before they can damage the sensitive equipment plugged into them.

For many years, the size of UPS commonly installed in network environments had been dropping as computers got smaller and more powerful. This put UPS buying decisions into the hands of network administrators with less involvement from electrical contractors. Now, as more critical operations move to various microprocessor-based environments, responsible facilities managers realize that a UPS is just as important for other computer-controlled systems (including telecom, security, and environmental control) as it has been for the network servers.

For the first time in many years, installations of larger UPSs are increasing rapidly, with expanding involvement from contractors, engineers, and others who can assist with "big picture" implementation throughout a facility. At the same time, the decision to use a UPS has become easier because new models are more cost effective and offer a selection of features suited for every environment including

Simple "plug-and-play" distribution options.

Hot swappable batteries and electronic components that simplify service requirements while maximizing uptime.

Modularity that allows contractors to add to power capacity and battery backup time as needs increase.

Redundancy of components to ensure there is no single point of failure.

Power management software that notifies users of problems or automatically saves work in progress.

Solving the power problem To justify a power protection plan, managers must first review several factors that represent the true cost of power-related damage. While disaster plans are often aimed at protecting physical equipment, its data and continuing operation often warrant far more protection. It's easy for the accounting department to keep track of the value of a piece of hardware that can be damaged, but in reality the data stored on, or services performed by, that hardware are almost always of more value than the machine itself. Factors to consider include:

The cost of downtime for each station (including the cost of productivity losses when shared peripherals become unavailable or damaged).

The value of the hardware.

The value of the data on each computer.

How long it takes after a power failure, brownout, or other disturbance to restart a system and restore full productivity.

New power protection devices aimed at this new breed of enterprise-wide operations include the Symmetra PowerArray from American Power Conversion Corp. of West Kingston, R.I. This approach to backup power is scalable from 4 kVA to 16 kVA (single-phase) and offers backup times from several minutes to many hours depending on user requirements. It can be repaired in minutes without having to power down the connected equipment using hot-swappable components and assures continuous availability through "N+1 redundancy" using a new power-sharing technology in which all of the modules run in parallel, sharing the load evenly. N+1 redundancy-a feature often implemented in computer drive arrays, power supplies, and processors-means running one extra module than will support the users full load.

If a module fails or is removed, the other modules instantaneously begin supporting the full load.

If it's important, back it up All sensitive electronic devices, whether used in the smallest home or the largest industrial facility, can be harmed by bad power. These days, the term "sensitive electronics" applies to much more than servers and PCs. Everything from a company's telecommunications operations to its security systems use technology that can be damaged by bad power. Although many of the problems-like power surges and sags-are invisible, they increase the wear on equipment. The moral: If you don't want to replace it, protect it.

UPS selection checklist Here's a simple review of things that contractors should consider when recommending a UPS for an installation.

How much backup time is needed? Most power failures last less than a few minutes, but every situation requires an individual evaluation. Typically, computer users expect a minimum of 5 to 10 minutes of backup so they can perform a safe system shutdown either manually or automatically with power management software. Other applications have varying needs depending upon how close to 100% uptime users require or how difficult it is to restart systems once they go down.

What happens when the batteries need to be replaced? The unit should provide notification via audible alarm, front panel display, and software interface to notify users. To avoid expensive downtime, the batteries should be hot-swappable-meaning they can be replaced while all connected equipment is up and running.

Does the UPS offer redundancy to assure that there is no single point of failure? For applications that require "high availability" uptime close to 99.95%, look for a power system that offers N+1 redundancy. Traditional UPSs typically assure 95% uptime, which may be suitable for applications where it is possible to schedule shutdowns for maintenance but is unacceptable for high availability needs.

Is remote monitoring and control of the power to the system required? Power management software allows users to monitor and control power remotely via server, PC, or the Web with a variety of built-in security features.

Does the unit meet appropriate established safety and performance standards? Any UPS installed should be listed by UL (or CSA in Canada), should pass the IEEE 587 Category A 6 V test for normal mode surge voltage let through, and should meet FCC Title 47 Part 15 EMI standards. Any power management software should be certified to work with whatever operating systems are used.

List all equipment that should be connected to the UPS. As discussed above, consider anything that contains vital files or performs a critical function including all security devices, monitors and telecommunications/internetwork-ing hardware that convey vital information.

Virtually all UPSs are rated in Volt Amps (VA). Although most electronic equipment includes a rating label that lists its input voltage and power requirements in Amps or Watts, virtually all UPSs are rated in Volt Amps (VA). Multiply voltage times Amps to determine VA. If only Watts are listed, multiply the wattage by 1.4.

Add the VA requirements for all of the components. Choose a UPS with a VA capacity at least as large as the system total requirement. You may want to select a scaleable UPS or oversize the UPS to allow for future growth.

Is it possible to upgrade the UPS when longer battery backup times or higher power levels are required? Newer UPS designs with upgradeable modules will allow for future expansion in both of these areas.

Where is the equipment located? If all critical equipment is located in one area, it makes sense to connect all devices into one larger UPS. If devices are in different locations, using several smaller UPSs is often the most cost-effective solution. Contractors can also choose to install the UPS in a central location to power a distribution panel that provides power to select areas of a facility.