The sudden spotlight on security and disaster recovery in the technical press owes its urgency, of course, to the new reality of terrorist attack on U.S. soil. For example, when the World Trade Center disaster disrupted the 80 megawatts of power normally flowing into the center and its environs, uninterruptible power supplies (UPSs) in surrounding offices kicked in, as well as the occasional diesel generator to keep freight elevators, telecom switches, and minimal services running. A closer focus on the power protection market, however, shows that the spike in interest precedes September 11, dating back instead to California's energy crises of the past year.

UPSs have been pressed into service frequently during the power alerts commonly called in California by the state's main power grid manager. A Stage Two Alert, for example, happens when the power supply gets to within 5% of the projected demand. Voltage drops and brownouts occur, damaging unprotected computer power supplies and delicate electronics.

Fortunately, many UPSs have what's called a ferroresonant transformer that corrects brownouts. And when things really get tough, many UPSs can now be controlled remotely via software, allowing offsite managers to selectively and gracefully power down unessential power consumers, and reduce overall power consumption to help stave off Stage Three alerts (power reserves below 1.5%) and/or blackouts.

David Slotten, director of product management at UPS maker Tripp Lite, says UPS management software started out as a way to monitor UPSs at remote sites with a single GUI interface. It has since leveraged IP to allow Tripp Lite to monitor UPS systems globally, even across different platforms and manufacturers. Most important, "it's become more action-oriented, so you can remotely toggle outlets on and off. If power becomes scarce you can shed loads that don't need to be backed up and extend the runtime for those that do. Or, if you've got a router hung up out there, you can toggle a UPS outlet and get it going again."

Tripp Lite's PowerAlert v. 11.0 software provides network power control from any web-enabled device, including the industry's first support for wireless phones and Palm Pilot PDAs. A new Wireless Application Protocol (WAP) web server converts PowerAlert's normal GUI into a text form compatible with all wireless Internet browsers. Now, instead of logging into a workstation, you can check UPS status, reboot outlets, or power down devices from a WAP phone or wireless PDA. And PowerAlert can automatically contact administrators during power events via email, pager, PDA, or WAP phone.

UPSs have gotten smarter as well as remotely controllable. Many now have embedded processors and software that support various ways of communicating with PCs. For example, you can insert a Simple Network Management Protocol (SNMP) network card in the "smart slot" of some UPSs, then connect this to the serial or USB port of your networked PC; or the UPS may have its own Ethernet network card and IP address, allowing it to be managed by network management software such as HP OpenView. Some UPSs have modems for dial-in diagnostics if the data network goes down.

POWER PROTECTION 101

Before you run out and buy a UPS with all the bells and whistles, you've got to make sure that its operating characteristics are carefully tailored to the needs of your application.

The most common mistake made in buying a UPS is looking at its "VA number" and confusing this power measurement (called "volt-amps") with watts. In grade school we were taught that watts equals volts multiplied by amps. So if you've got a fault-resilient computer running an SS7 node, telecom switch, or web server, and it needs 1,000 watts or 1 kilowatt hour (1 kWH), then you should run out and buy a UPS with a 1,000 VA (1 kVA) rating, right?

Wrong. No electrical device is 100% efficient in the way it handles power. This inefficiency is rated in a little number, called a power factor, found somewhere in the fine print of UPS documentation. Ranging between 0 and 1, it's multiplied with the VA number to get the real number of watts that can be output by a UPS or consumed by a product. In the example above, if the power factor of the 1,000 VA UPS is, say, 0.7, then your UPS actually can handle a load of 700 watts. Of course, this works the other way - because of the power factor, your 1,000 watt PC may not be gulping 1,000 watts. Older PC power supplies produced "non linear" loads, with a power factor rating of 0.65 to 0.7.

Today, however, new power supplies are "Power Factor Corrected," which means they draw low distortion current from the AC source, and have a power factor rating of nearly 1. So it's a good idea, as ever, to somewhat overprovision your UPS.

And also as ever, you get what you pay for. Standby UPSs are the most primitive, switching to battery power when utility power fails. These also offer a modicum of surge and line noise protection. More sophisticated line interactive systems also switch to batteries in case of a surge (lightning strike or major switching of loads by a utility), a "sag" (brief voltage loss) or a more severe brownout. Sags and brownouts can insidiously wear out your computer power supply and often result in a spurious "freezing" of PCs that force you to reboot.

Cheaper UPS units are "noisy" and produce pseudo-sinewave or squarewave AC waveform outputs that may be incompatible with delicate electrical devices or other surge suppressors in your power chain.

UPS maker Sutton Designs (Ithaca, NY - 607-277-4301, www.suttonde signs.com) says that if you're powering a computer that contains a power supply with surge suppression and/or noise filtering circuits, the UPS should at least produce a quasi-sinewave and should have a manufacturer's stated THD (Total Harmonic Distortion) of less than 28%, when measured with a real-world, switched-mode power supply load (not a simple pure resistive load).

The best UPSs, called "online" systems, are what's required for critical systems like telecom switches, routers, multimedia servers, large call centers, or equipment in the service provider infrastructure. These units use "double-conversion" technology, which means that the incoming AC power goes through the battery, is converted to DC, then is converted back to AC (or it can be left as DC if a lot of -48 VDC central office power is needed).

By isolating the output energy from the main utilities, online units exhibit no delay in switching from utility to battery power. Also, special circuitry reproduces a pure voltage sinewave for AC output, giving you the "cleanest" AC power possible, with a THD of between 2% and 5%.

CALMING THE WAVES

Indeed, the power conditioning aspects of a UPS or power system can be just as important as its backup. Research by IBM indicates that up to 45% of all computer and electronics malfunctions leading to data loss are attributable to the effects of power disturbances.