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Power To The Core
Interruption of utility service can force FMs to recognize the importance of data preservation.
By Carey O’Connor & Henk Vande Wetering
Currently, the United States loses $80 billion per year due to power outages and interruptions, and the losses are accelerating. Utility demand continues to amplify. So how reliable are power sources? And how reliable will they be in three years? More importantly, how valuable is the facility department’s time and the company’s data?
Anyone responsible for an organization’s data center is expected to maintain data access and integrity without interruption. But there are several key elements necessary to establish consistent, reliable power in these types of facilities.
Get To Know Your Backup
First and foremost, a manager must understand all components of a power quality system and know how they function together. Second, a strong, viable maintenance routine that provides a high level of security must be instituted. Finally, a facility manager must be able to respond to any issues detected during maintenance and prevent any major load loss.
Currently, the best power continuity solution for data centers is an uninterruptible power supply (UPS) system and generator for all critical systems. UPS systems manage the transition to generators in the event of sustained power outages and are very effective during power interruptions that are minimal in duration.
Some larger data centers also require that a second utility, one from a different substation or grid, be used as a backup or shared AC source, thus increasing the overall protection of the data center. However, properly designed and implemented, UPS systems and related peripherals can manage all necessary power requirements.
What Happens During A Power Surge?
Design run time criterion for UPS applications is typically 10 to 15 minutes. During a 15 minute outage, a complex sequence of events occurs. The UPS recognizes that the input power vanished; the battery associated with the UPS ensures power integrity; and the generator starts and maintains power. The UPS then cycles to generator power, and the battery begins recharging.
Unfortunately, many things can go wrong during this sequence of events. Often, if the UPS system fails, it is due to the batteries.
Batteries are the least reliable component of the UPS. The chemical reaction that creates the DC current in batteries renders them extremely sensitive to any deviation in temperature, barometric pressure, or humidity. Moreover, variances in charging profiles and the type and duration of discharge events drastically alter the lifespan and performance of the lead acid cell. Add to this linear deterioration caused by age, and the result is the dramatically variable operation of a constantly degrading system.
Battery Testing
Although predictive failure analysis is very difficult, some companies have made advances in resistance and conductance battery testing instrumentation. One assessment factor consists of the length of the battery’s service.
After a certain time, the chances of cell failure become statistically relevant and increase exponentially. Without redundant battery “strings,” an open DC cell renders the available current and voltage to the UPS at a zero level. So during a power outage, the UPS would be unable to support any load, the data center would go down, and the firm would be hemorrhaging money.
While most components remain functional throughout the life of the UPS, batteries require replacement every two to five years. The battery is also one of the most expensive components of the UPS, typically accounting for 25% or more of the initial purchase cost. Consequently, for a UPS with a service life of 10 years and a battery life of two years, the total cost of battery replacement will equal or exceed the original purchase cost of the UPS.
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