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Organisations increasingly rely on the continuous and predictable power availability to support their ICT services. Uncertainty over the future of the UK electricity supply means it is now even more important than ever to implement a secure power strategy.
The OFGEM Electricity Capacity Assessment Report, published in 2012 predicts that business consumer concerns over power availability will grow over the coming years. The capacity issues are a direct result of reductions in electricity supplies from traditional coal and oil power stations which are due to close under European environmental legislation.
How can data centre operators protect their ICT assets from the predicted increase in power interruptions?
Uninterruptible Power Supply (UPS)
An Uninterruptible Power Supply (UPS) provides the first line of defence protecting the critical load from power disturbances and blackouts. UPS systems are designed to support continuous high quality power to the ICT services using battery power reserves until normal supply is restored.
The duration that the UPS can support the load is limited by the battery capacity. The majority of mains outages last less than 5 minutes. Battery autonomy can be increased by adding extra external battery cabinets, but these consume space and require continuous maintenance and have a limited operational life requiring replacement every 3 to 7 years depending on battery type.
Typically, data centre cooling systems are not supported via the UPS. Without cooling, the continued operation of the critical load will lead to thermal runaway, which in turn can damage I.T equipment. Therefore extending battery autonomy is not recommended without the ability to maintain cooling.
It is possible to configure a signal to provide controlled I.T shutdown before the battery autonomy is exhausted. Whilst a controlled shutdown is preferable to simply losing power and crashing disks, loss of ICT resource is very often not acceptable to many organisations. Backing up the UPS with a standby generator is the only alternative option.
The UPS system will protect the ICT load from power disturbances and short-term power failures enabling enough time for a backup standby generator to start up and come on line to maintain both critical and mechanical services.
Generator Systems
Diesel powered standby generators are configured with an engine that drives the alternator which in turn provides the electrical output. Standby generators should be well maintained and must be ready to start on demand with an adequate supply of fuel.
Under mains failure conditions, the UPS will initially maintain power to the critical load. The generator will detect mains failure through the Automatic Mains Failure (AMF) panel The standby generator must be sufficiently sized to support both UPS / battery recharge as well as mechanical services.
During start-up, it is essential that the generator should not be presented with the entire facility load to avoid a potential engine stall. This is achieved by implementing a ‘soft start’ scheme by programming sequenced time delays within mechanical services equipment. It is also possible to programme time delays and “walk in” load transfers on UPS equipment. Typically, generators should be fitted with electronic rather than mechanical governors, allowing operation within tight frequency tolerances.
The AMF panel will also detect when mains power is restored, and, after a pre-set delay will switch back to the mains supply.
Given the predicted increase concerns in electricity availability, generators should be an essential addition to UPS backup in any mission critical application where interruption of data cannot be tolerated.
Workspace Technology provides a comprehensive range of power continuity solutions including UPS, Generators, Switchgear and complete design and installation services. Workspace Technology’s expertise within data centre and 24/7 mission critical environments is extensive.
For further information on Workspace Technology Power Generation division please contact us or call 0121 354 4894.