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The LexisNexis data center in Miamisburg, Ohio, operates 24 hours a day to supply 2.6 million subscribers with legal, corporate, government and academic information. The 45,000-sq.-ft. facility has hundreds of mainframes, servers, workstations and storage devices. Jerry Zahora, consulting systems engineer at LexisNexis, faced a huge task: The only exception to the center's round-the-clock servi...
The LexisNexis data center in Miamisburg, Ohio, operates 24 hours a day to supply 2.6 million subscribers with legal, corporate, government and academic information. The 45,000-sq.-ft. facility has hundreds of mainframes, servers, workstations and storage devices.
Jerry Zahora, consulting systems engineer at LexisNexis, faced a huge task: The only exception to the center’s round-the-clock service was an 8-hour maintenance window on Sunday mornings that needed to be closed because it was affecting international customers. Zahora’s plan was to enhance backup power, but also, to find the causes of power glitches. So he looked to an automated power monitoring and analysis system for help.
Exactly fifty metering devices were installed to capture power-event and energy data at high-voltage 12.47-kV to 480-V transformers, uninterruptible power supply (UPS) outputs and the static switches that transfer loads between UPS systems. Metering equipment, which gathers load data from the automatic transfer switches (ATSs) and 20 power-distribution units are linked via Ethernet to a server that runs the monitoring software.
Alarms, reports and waveform analysis are displayed at five workstations. “We’re creating custom screens where we can ‘walk’ around our one-line electrical diagram and look at a batch of meters,” explains Zahora. “We can see all meters in a substation at once instead of calling up each individually.”
One challenge was backup power for UPS maintenance. The UPS units were already in a parallel redundant configuration, so if one UPS were down, its load would be redistributed automatically among the remaining modules.
“We installed another large UPS system that could back up any of the five existing UPS systems,” Zahora explains, “as well as the monitoring system that could track where the loads were. This gave us the flexibility to move loads around with the use of static switches, if we had to do maintenance or react to a failure. Now if we want to work on an ATS, we can move the loads, take down a UPS and not worry about any downtime.”
The next goal was capturing more information about voltage spikes and other power-quality events. Many alarms, such as for voltage imbalance and overcurrent, are reported by the monitoring system to the building automation system, which instantly notifies maintenance of any urgent problems. “We’ve configured the software to send messages describing the condition and location,” says Zahora, “for example, ‘UPS 10 has a transient.’ In the future, I’ll also set up the software to call my pager and send text messages directly to me.”
Some key pieces of information captured by the power monitoring system are voltage and current waveforms. They convey a great deal about the causes of power quality events like transients, sags/swells, outages and harmonics.
“Every waveform has a signature. I compare suspicious waveforms recorded by the meters with the ones in my reference book. By checking vectors and degrees, I can identify two or three possibilities for the source of a problem,” says Zahora.
One night, all eight of the switches transferred power from the new UPS. At first, no one knew why. Then Zahora checked the waveforms and they all pointed to the source that was feeding the switches—the UPS itself. Capacitors on the output filter had shorted. “Without the meters,” Zahora remembers, “we would have wasted a lot of time troubleshooting the problem and may never have known the cause.”
Another disturbance was reported every morning at 7:28 a.m. by a meter on an incoming substation feed. The waveform revealed an oscillatory transient that was probably the result of a utility capacitor bank. Zahora phoned the utility and confirmed that a capacitor bank was indeed being switched on at that time.
Zahora also discovered the reason for some static switch alarms. The meters recorded transients on the voltage waveforms when LexisNexis transferred from emergency generators back to the utility feed. The associated current waveforms revealed a dip in the incoming utility current, which wasn’t supposed to happen with a closed-transition transfer switch. LexisNexis wasn’t dropping any loads either. The only explanation was that some current was temporarily being drawn from the UPS batteries, which set off the connected static switch alarms.
“In training, I learned how to program an alarm on an emergency generator so the transient sensors weren’t activated until after the generator started running. If I had set up a standard alarm, it would have been on all the time because, when the generator switches on, the voltage instantly changes from 0 volts to 480 volts, above the nominal 280 volts.
“I made these changes on the meters remotely through software, without any hard-wiring. I just modified a few modules and linked them graphically on my workstation,” explains Zahora.
Another custom setup was to confirm whether the transient voltage surge suppressors were working properly. The TVSSs prevent high voltages from passing into the data center if it’s hit by lightning. On his workstation, Zahora can see the highest voltage and current actually allowed through.
It’s just as important to exclude unnecessary details as it is to gather data. That way, Zahora can decipher the important facts faster. “I learned some tricks about eliminating extra waveforms that I don’t need. That’s what I like about the system. You can do just about anything you want, and get meaningful data that gives you tremendous insight into every situation.”
He’s now analyzing the feasibility of incorporating LexisNexis remote “phone rooms”—2,000-sq.-ft. sites that route communications traffic back to Miamisburg headquarters—into the company’s Ethernet network, so he can bring any site in the country onto his computer screen as easily as if it were right next door.
From Pure Power, Fall 2002