With falling corporate budgets and rising energy costs, mission critical facility operators need cost-effective power distribution. The most common power distribution practices provide the facility power at medium voltage (2400 V to 35 KV) and then step down to distribute power at 480 V to critical loads. This “step-down” approach can be a costly mistake since there are typically inherent efficiency losses and cost increases associated with this basic design.
One solution is to focus on the power distribution infrastructure and incorporate a medium voltage uninterruptible power supply (UPS) to ensure the most efficient power distribution.
People are usually surprised at how inefficiently their electrical infrastructure performs. Digital Realty Trust's recent survey of IT-dependent businesses found the average Power Usage Effectiveness (PUE) rating at 2.9 across the industry. Compare that to some facilities that operate at an achievable 1.7-1.9 and you’ve got an efficiency issue.
In a traditional electrical distribution system there is a series of power exchanges that require energy to be reduced accordingly. When power is received from the utility at medium voltage (2400V-35KV) and transformed to 480 V for distribution, which requires several steps:
1) Utility/Power Source: Supplies power to the facility at medium voltage.
2) Primary Transformers: Power is stepped-down to “distribution voltage” (480 V) at the substation transformer.
3) UPS/PDU: Power is stepped-down again to 280/120 V by a power distribution unit (PDU).
4) IT Equipment: Power is stepped down a third time to 12Vdc, the operating voltage for most server and storage gear.
Use of this model means more added costs and greater inefficiencies in each step of the power infrastructure.
Advantages of Medium Voltage
Transitioning to a medium voltage system offers physical cost savings. Medium voltage systems require smaller or fewer conductors, which eliminate the need for expensive copper. They also avoid the voltage drop of 480V systems so there is no reduction of supplied energy as the current runs through a circuit. The more voltage drops, the greater the inefficiencies that result in lost power. Also, medium voltage systems do not have the heat and associated cooling costs associated with a lower voltage system.
UPS vs DRUPS
Typically, a UPS provides emergency, stored power to a load when the main input source fails, ensuring instantaneous protection from power interruptions. This is often one of the biggest roadblocks to transitioning to a cost-effective medium-voltage model. Typical UPS systems are static and powered with a battery that provides the energy source in case of failure. But standard UPS systems were not designed to handle a medium-voltage load. This has increasingly led companies to turn to a Diesel Rotary Uninterruptible Power Supply (DRUPS) to support the load with a diesel generator, and provide continuous backup as needed.
Modern DRUPS systems are designed to condition power at medium voltage, without the use of transformers. They operate at 97% to 98% efficiency, far higher than static systems, at a rate that minimizes losses.
One medium-voltage DRUPS unit alone can reduce a facility’s PUE by several points – not to mention the amount of money saved in energy over the lifecycle of the building.
An infrastructure operated at medium voltage is a smart, simple, and reliable alternative that offers increased efficiencies and decreased costs. Investing in a DRUPS system can help remove step-up/step-down roadblocks and offer a medium-voltage system designed to meet growing data center cost and efficiency needs.
David Mazur is chief technologist and vice president, sales and marketing for Hitec Power Protection, Inc. and can be reached at email@example.com.
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