It was an ambitious project, even for real-estate power-houses like Sterling Capital Ltd. and Cushman Wakefield. In November 1999, the conversion began. The 360,000-sq-ft building that once housed The Arizona Republic became Phoenix's largest telecommunications data hotel. Within six months, the newly named Downtown Phoenix Technology Exchange (DPTE) housed such telecom heavyweights as Time Warner Telecom, AT&T, Cox Communications, Metromedia Fiber Networks, Level (3) Communications, and XO Communications. All of this highly sensitive, state-of-the-art equipment in a multitenant environment demanded the highest possible power quality.
Aside from 24/7 power requirements, the building owners needed a system with advanced monitoring capabilities — an important factor in managing contracts with the local utility. Advanced monitoring features would enable DPTE engineers to track the tenants' usage and recoup the appropriate costs.
In addition, advanced monitoring would allow DPTE engineers to isolate a problem quickly — before it became a major issue.
“A tenant might come to us and say, ‘you're selling me contaminated power,’” explains Tony Wanger, a partner in Sterling Capital's real estate group. “We need to be able to show them that what we're passing through is exactly what we get from the local utility.”
The Right Stuff
With these objectives in mind, the project engineers researched several power quality monitoring/software systems. They chose the Multipoint Power Recorder (MPR) from Reliable Power Meters for its ability to keep the most detailed and the highest volume of data. Later, they installed Reliable's Scenario software for use in analyzing and interpreting the data.
The MPR's meter consists of a data-gathering module that's installed inside the switchgear (see photo). It has its own current transformers (CTs) that sense 5A current loops from CTs embedded in the switchgear. For voltage, the meter connects directly to 120V potential transformers (PTs) in the switchgear.
The switchgear connects to DPTE's central computer (onsite or remote) via different kinds of communication systems (Ethernet, etc.). Using dedicated phone lines or the Internet allows the data to be exported and displayed on any computer that's properly programmed. DPTE personnel monitor at the line side of their service section and at each tenant's section.
Advanced monitors like the MPR differ from traditional monitors in two respects. The first involves thresholds and set points. Traditional monitors set metering thresholds based on the CBEMA curve. But when monitors operate with thresholds, underlying information that indicates deteriorating conditions is filtered out and lost. This area below the threshold creates a “dead zone” of untapped data. The MPR requires no thresholds or set points to isolate disturbances (see Fig 1).
The second difference between traditional and advanced monitoring is predictive maintenance capability. The MPR measures and records every aspect of electrical power simultaneously. It captures minute measurements well below the thresholds set by traditional PQ monitors, making it both a prognostic and diagnostic tool. Power data is tracked and then displayed using software so that the user can “see” variations that may lead to problems. The MPR, for example, measures the following parameters without the need to change or load hardware or software modules:
- Flicker (IEC 868, Pst and Plt)
- Harmonics (THD, real-time harmonic spectrum with magnitude, phase angle, voltage and current, and long-term summaries up to the 63rd harmonic)
- Power consumption (usage; apparent, real, and reactive power; power factor; and displacement power factor)
- Power quality (sags, swells, transients, frequency, impedance, and long-term trends of rms voltages and currents)
In short, the MPR tracks conditions over time so that degradation in power systems becomes apparent.
System in Action
One of the prime reasons the building owners decided to install a power quality monitoring system was to protect DPTE from tenant complaints. Eight months after engineers installed the MPR, a transient voltage surge suppressor at a tenant's location literally exploded. At first, the tenant insisted that contaminated utility power was to blame for the damaged equipment. The MPR, however, had already gathered extensive data, and with the Scenario software, DPTE engineers were able to prove that the power supplied by the utility had been clean. Ultimately, the engineers identified a manufacturing error as the cause of the explosion.
Other benefits of the software include the ability to create baselines, set alarm limits, and trend out all the values in one graphics screen. This last feature allows the user to pick out and display specific data.
Although power quality monitoring was the foremost consideration for the project engineers, energy tracking wasn't overlooked. Landlords of multitenant data centers like the DPTE typically collect building drawings for each tenant, calculate the load required for each space, and allot a percentage of the total load to each tenant. If the estimated power demand is inaccurate, the landlord must come back six months or a year later with metering records that prove actual demand.
Currently, DPTE engineers supply a minimum of 50W per square foot averaged over the entire building area of 360,000 sq ft. One DPTE tenant had requested 150kW of power capacity. The MPR tracked an average actual energy usage of only 45kW, allowing DPTE engineers to more accurately reallocate the tenant's portion.
DPTE's owners and engineers are pleased with the benefits they have received from the MPR monitoring system and Scenario software. In a move that reflects their confidence in the equipment, Reliable Power Meter's equipment specifications were recently written into DPTE's building manual, and each tenant is now required to install an MPR. Today, DPTE's approach to power quality monitoring has become an important factor in attracting tenants to the facility. As Sterling Capital's Tony Wanger puts it: “This data center application demonstrates that power quality monitoring is a necessary adjunct to modern system maintenance.”
Marsha Lisak is the former managing editor for Power Quality magazine. She is currently a feature writer for WelComm Inc. You can reach her at email@example.com.