Author:
Alan Luscombe, Sales and Marketing Director, Uninterruptible Power Supplies Ltd (UPSL)
Date
04/01/2010
PDF
A tailored and integrated approach to power protection, comprising modular UPS and fully-matched standby generators, is helping businesses sustain vital uptime and availability. Changes in the business landscape, the growing risk of nationwide power cuts, and advances in technology are accelerating the uptake of more flexible and efficient UPS systems. With global 24/7 online trading and customer expectations of immediate, anytime availability, power continuity around-the-clock is often essential: in highly competitive markets even a minor interruption to business systems can cause considerable revenue losses. Whether due to planned maintenance or unplanned power outages, system downtime is undesirable - and increasingly unacceptable for business critical loads. The UK's ageing power stations and unproven alternatives are a major cause for concern and should spur organisations to urgently review and reinforce their power protection systems, to ensure they can cope with unreliable supply, more frequent interruptions, and the possibility of long term power cuts.
Transformerless three-phase UPS technology, introduced in the early 1990s and now widely adopted, delivered significant weight and space savings and enabled the development of rack-mounted modular UPS systems.
Compared with traditional free-standing units, these units can reduced the required floor space by 75%, and vertically scalable modules mean that additional capacity for redundancy or load upgrades can be easily achieved at a fraction of the cost of adding an additional stand-alone unit. Going back just a decade, only 10% of three-phase UPSs were parallel redundant systems but today this configuration accounts for more than 70% of installations. The majority of organisations needing protection for critical loads are upgrading to parallel redundancy, providing a minimum of one UPS over and above that required for capacity and ensuring continuous support of the load if any one UPS shuts down. When specifying a UPS system, it can be difficult to predict what the power requirement is going to be so installations are often over-sized to provide contingency, creating a wasteful gap between installed capacity and the size of the actual critical load. While this may ensure sufficient UPS capacity, it means inefficient operation, additional expense and inefficient use of energy and costly floor space. However, rack-mounted modular UPS configurations can be cost-effectively ‘right-sized' from outset more easily by inserting or removing ‘hot-swappable' modules, enabling power to be added as requirements grow without downtime or increasing footprint. Hot-swap technology, along with significant reductions in repair time, can also achieve six nines availability (99.9999%) - highly desirable in the pursuit of zero downtime. Modularity improves efficiency by working closer to the load capacity than traditional UPSs but without sacrificing the security of the system. The more a load approaches the capacity of any UPS, the more efficiently the UPS operates. A traditional stand-alone parallel redundant system is typically just 50% loaded while a modular solution typically achieves a 70% or higher loading. This reduces energy use, Co2 emissions and UPS cooling requirements.
Compare a single stand-alone non-redundant 100kVA UPS solution with a parallel redundant 3 x 50kVA UPS modular solution. While the latter may carry a price premium, the cost-benefit is quickly apparent. The modular configuration provides redundancy if one of the units fails, and modules can be added to accommodate an increase in capacity, in affordable, incremental steps without interruption to the critical load. The stand-alone system provides no redundancy and the addition of a second parallel 100kVA unit to increase capacity would be more costly, take up twice the space, and would also incur downtime during installation. Price sensitivity is understandable, especially in the current market where expenditure on capital equipment may be subject to tougher scrutiny. However, while the purchase price of a traditional standalone UPS system can be typically 10% to 15% less than an advanced modular UPS system, Total Cost of Ownership should be considered. The lower purchase price of traditional standalone UPS technology must be offset against significantly higher operating expenses in comparison with a modular system based on technology which reduces energy loss costs. In fact the higher initial price of the modular system can be recovered within the first year of operation, and a comparison of additional long-term costs also favours modular technology. For example, approximately £150,000 could be saved over five years by replacing a ten year old 400kVA parallel redundant UPS system, running at half of its rated capacity, with a new Decentralised Parallel Architecture (DPA) 200kVA parallel redundant UPS system. This would also reduce CO2 emissions by over 700 tonnes and cut floor space by 70 percent. Upgrading a traditional UPS demands extra space, costly cabling and potentially involves taking the UPS system off-line during the upgrade. With a modular UPS, the upgrade is performed by simply inserting the additional power modules into the rack, without any interruption to the load, without increasing the footprint, and with no additional work on site. This flexibility makes upgrading a system very easy, and with little additional cost.
There may be situations where organisations can tolerate occasional downtime, and in this case a UPS fitted with a standard or extended autonomy battery may provide the required system integrity. However, where downtime is untenable, a standby generator with automatic mains failure (AMF) detection and changeover facilities will be 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. Round-the-clock dependence on uninterrupted critical loads means that this seamless interaction between UPS and standby generators is an important requirement. Turnkey supply and installation also 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 generator ensures a true ‘no-break' supply in the event of a mains failure - protecting critical loads and assuring uptime. www.upspower.co.uk
