Published on Friday, Dec 18 2009 by
No longer simply a backup plan, power protection is firmly at the forefront of business continuity and secure communications, keeping vital systems and networks running around-the-clock. With the threat of an impending energy crisis, Alan Luscombe of Uninterruptible Power Supplies Ltd (UPSL) explains how integrated UPS and standby generator solutions can ensure continuous system uptime.
Analyst warnings of regular nationwide power cuts as early as 2012 are contradicted by expert assurances that supply shortfalls will be avoided. Objectively this presents a very hazy future. The only clear message is that organisations must be prepared for an uncertain supply scenario and safeguard critical loads against interruptions. Until a clearer energy policy emerges, trusting that the ‘generation gap’ will be bridged would be a high risk strategy. If predicted power cuts become a reality in three years’ time, the potential for compromised supply at the London Olympics for example will add yet another dimension to the many logistical and security challenges already facing the event; the sites and venues will be alive with wireless communications and system operators will need a robust power protection strategy to ensure network integrity.
The UK’s aging power stations and inadequacies in the distribution infrastructure are unquestionably a cause for concern, andthousands of organisations every year already endure power cuts and fluctuations, adversely affecting IT and communications equipment and causing service disruptions and loss of business.
The vulnerability of the utility mains should spur organisations to urgently review and reinforce their power protection systems to ensure they can cope with deteriorating supply, more frequent interruptions, and longer term power cuts.
It is not only total mains failures or ‘blackouts’ however which can trigger devastating effects. Many electrical loads are equally susceptible to power sags, brown-outs, spikes and surges, noise and radio frequency interference, and supply frequency changes. Such critical loads require a more stable and reliable source of power than is generally offered by the national grid.
Uninterrupted power
There may be situations where an organisation could tolerate occasional communication blackouts, and in this case an Uninterruptible Power Supply (UPS) fitted with a standard or extended autonomy battery may provide the required system integrity. For example, a 20kVA UPS may be supplied with a 10 minute battery as standard but by adding another cabinet it is possible to extend the autonomy time to 30 minutes. During a prolonged mains interruption, the UPS will support the load equipment for the battery autonomy time and then signal the load to perform an orderly shutdown, assuming that suitable shutdown software is available and running.
However, the notion of an orderly shutdown is of course unthinkable for many critical communications systems, where even an outage of a few seconds can pose a serious health and safety risk or disruption to commercial operations.
Statistically, while 95% of all mains disturbances last for less than five minutes, anything longer is likely to last for many hours. But regardless of duration, where applications must be available at all times without interruption, a standby generator with automatic mains failure (AMF) detection and changeover facilities is a vital part of the protected power supply system. During a mains supply failure, the UPS battery will support the load for the time it takes the generator to start, stabilise and be switched over to supply the UPS. Assuming the generator has been correctly sized for the application, the UPS will accept the generator as a ‘mains replacement’, start to recharge the battery and continue to supply the critical load for the duration of the interruption.
Growing expectations and dependence on 24/7 operation of mission critical systems conflicts with increasing uncertainty over mains quality and supply. This puts power protection at the frontline of network security.
Protection
Communication centres most often use medium-sized UPS systems in the 3–20kVA power range but larger loads may require high-power systems, typically rated from 30–300kVA. Especially for critical load applications, such UPSs would include facilities for remote alarms and status indications. Mini-systems offer a portable solution for low power applications in the 500-200VA range.
Periodic assessment of power demands and UPS capacities is vital since the continued growth of IT and comms systems means that the level of protection provided by legacy UPS installations has in many cases been outstripped, leaving them incorrectly sized for increased loads and all the more exposed to mains failures. Single modules of up to 800kVA are available, but for efficiency, availability and scalability reasons it is increasingly common for large loads to be powered by UPS systems which comprise several ‘high power’ modules operating in parallel. Traditional stand-alone systems, with their inherent single points of failure, are increasingly outmoded.
Trying to cater for future power requirements with stand-alone UPSs can also lead to over-specification, creating a wasteful gap between installed capacity and the size of the actual critical load, and making inefficient use of costly and frequently limited floor space. However, rack-mounted modular configurations can be right-sized by inserting or removing ‘hot-swappable’ modules, enabling power to be added as requirements grow without any footprint penalty. This hot-swap technology, along with significant reductions in repair time, can also achieve six nines availability (99.9999 percent) - highly desirable in the pursuit of guaranteed uptime and an important factor when mains supply in the UK is becoming less dependable but more critical to business operations.
The majority of organisations seeking protection for critical loads are migrating to parallel redundant UPS systems, providing a minimum of one module over and above that required for capacity and ensuring continuous support of the load if any single module shuts down.
There is an outmoded view that redundancy is only for large scale applications such as data centres or call centres, but UPS technology has evolved and the installation of a parallel redundant UPS configuration is in fact both practical and affordable for much smaller organisations, and highly desirable for critical applications of almost any size.
A decade ago, only 10 percent of three-phase UPSs were parallel redundant systems but today, even for lower rated three-phase systems, parallel redundancy now accounts for more than 70 percent of installations. Transformerless UPSs and the development of Decentralised Parallel Architecture (DPA) have significantly reduced unit size compared with free-standing legacy systems. By comparison, today’s rack format modular UPSs take up only 25 percent of the floor space, and vertically scalable modules mean that additional capacity for redundancy or load upgrades can be achieved without any footprint penalty. Further, doubling capacity does not mean doubling expenditure – an N+1 configuration (compared with traditional 1+1) means that extra modules can be installed in an existing cabinet at a fraction of the cost of an additional stand-alone unit.
The importance of UPSs is generally well understood. However, with the prospect of more lengthy mains disruptions standby generators are an increasingly essential element of power protection systems, providing continuity until utility supply is restored.
Standby power
With rapid expansion of communication networks and the proliferation of mobile devices and applications, businesses and organisations have a growing dependence on electrical loads falling into the ‘critical’ category. Round-the-clock dependence on these critical loads makes seamless interaction between UPS and standby generators a vital development. Generator sets are available in a wide range of power ratings and configurations, including open, canopied and container units, either for purchase or short and long-term rental contracts.
Turnkey supply and installation delivers valuable integration benefits, ensuring fully matched UPS and generator systems, removing the problem of demarcation between different suppliers and eliminating potential points of failure. Individually sourced units can compromise system autonomy and presents a risk of mis-sizing, causing installation and commissioning problems. A packaged solution with fully matched UPS and standby generators ensures a true ‘no-break’ supply in the event of a mains failure.
For many businesses, the financial, operational, safety and security consequences of a sudden or extended power loss are unacceptable. Where critical communication systems must be available at all times without interruption, an integrated UPS and standby generator solution provides critical protection around-the-clock and an invaluable safeguard against an increasingly unpredictable national grid.
Protection for the protectors - Surrey Fire and Rescue Service
All Surrey Fire & Rescue (SFRS) 999 calls are routed into its Mobilising Control Centre, a core function which depends on continuous power supply for round-the-clock contact with 24 fire stations, mobile appliances and neighbouring brigades. With over 15,000 incidents a year, each typically involving multiple calls, system uptime is of paramount importance. The Service regards its UPS as a critical part of the infrastructure and when an upgrade became due, a live transfer to a temporary standby UPS was required while the new system was installed.
SFRS project manager Kieran Amos explains: “The installation process was absolutely key to meeting our contractual and user requirements. Due to the configuration of our legacy UPS system, we could not switch off the supply without losing power to both primary and secondary mobilising control systems, leaving us unable to receive 999 calls or to mobilise response resources.”
The contract was offered for competitive tender and Surrey County Council’s Procurement Team considered a number of bids, including one from the incumbent UPS supplier. The contract was awarded to Uninterruptible Supplies Ltd (UPSL) for supply and installation of a new 20kVA PowerWAVE 3000/T UPS.
Although pricing was important, the quality of both product and service was critical for successful transition to the new installation. UPSL devised a strategy for live transfer from the legacy system to a temporary standby UPS, and the dual feed capability of the PowerWAVE 3000/T facilitated the necessarily complex changeover operation. UPSL also installed external batteries to meet the Service’s requirement for extended autonomy.
“The technical and installation teams were excellent in both developing and implementing the installation plan,” comments Amos. “It was executed in a safe and professional manner and significantly mitigated the risk of power supply failure to our critical mobilising systems.”
PowerWAVE 3000/T Series is a single-phase output UPS with power options ranging from 7.5kVA to 20kVA. The system has been designed specifically for mid-size server rooms, networks, telecommunication systems, industrial processes and medical equipment. It is ideal for locations where a small footprint is essential or where the mains power is of variable quality, and for applications demanding long battery autonomy.
The new UPS has proven to be a well adapted and successful choice for the Mobilising Control Centre. The unit’s compact design and transformerless technology meant a footprint considerably smaller than the system it replaced.
Amos concludes: “We appreciate the PowerWAVE 3000/T’s ease of maintenance and user friendly operation. In particular, we find the system diagnosis and reporting functions extremely useful and a marked improvement on the earlier system’s user interface.”
Highly skilled control staff manage each call to assess the incident type, salient risk and location before providing critical safety advice and mobilising appropriate resources. Support continues until the incident is successfully resolved. This can include mobilisation of further resources and relief crews, and co-ordination of related services. The Mobilising Control Centre also provides significant further support to the Fire and Rescue Service, handling internal logistic and administrative procedures. The Mobilising Control Centre can be considered as the Service’s most fundamentally important core function, and one that must have a power supply resilient to mains failure or interruption.