Within a recent Uninterruptible Power Supplies Ltd survey, 75% of
the respondents reported a power outage within the last 12 months.
Users do not expect this situation to improve, with 78% seeing UK
power reliability as an increasingly major concern over the next ten
years. In this environment, any organisation using ICT equipment for
business-critical operations must use uninterruptible power supply
(UPS) protection. As the UPS system’s ability to respond reliably on
demand depends both on the quality of its hardware design elements
and of its suppliers’ support strategy, it’s worth reviewing both
these factors while planning a power protection policy.
Today, most UPS systems use transformerless technology instead of
the earlier transformer types. Advantages include energy benefits
from improved efficiency, reduced input current total harmonic
distortion (THDi) and a higher input power factor. Both capital and
operating costs are reduced. Audible noise is also reduced and
battery life is enhanced.
Arguably the most important benefit, however, is the size and weight
reduction yielded by a transformerless design. A 120 kVA UPS, for
example can be implemented as a 263 Kg unit with a 0.424 m²
footprint instead of an installation with a 1.32 m² footprint
weighing 1,200 Kg. This has enormous implications for flexibility
and reliability, because it allows UPS systems to be configured from
a set of rack-mounting modules rather than as monolithic floor
standing units.
Modular rack-mounting configurations offer a set of reliability
factors that, together, maximise power protection quality. Firstly,
the modules’ transformerless design can reduce premature battery
failure and increase mean time between failures (MTBF), due to the
ease of adding additional modules to achieve redundancy. Secondly, a
modular topology allows a sharply reduced mean time to repair (MTTR),
because a faulty module can be simply ‘hot swapped’, eliminating
lengthy on-site repair time. Increased MTBF and reduced MTTR
together contribute to greatly increased availability, with up to
‘six nines’ or 99.9999% being possible.
Thirdly, a set of UPS modules can have redundancy built-in
efficiently, providing resilience to failure.
For example an 80 kVA critical load requirement could be served by a
UPS rack containing five 20 kVA modules; the load remains fully
supported even if one module fails. And true system redundancy is
possible, because each module can be designed to operate
independently, with no common points of failure within the UPS
configuration.
To realise modular UPS technology’s full power protection potential,
it’s essential that users choose the right supplier together with
the right hardware. In fact, over 90% of the survey’s respondents
considered their UPS supplier’s maintenance and emergency callout
support as important to their business as the hardware itself.
Ultimately, the best strategy is to work with a supplier who becomes
a power protection partner.
For example, many organisations now consider a generator as a
desirable or even essential complement to their UPS within their
power protection strategy. So, can the UPS supplier offer a matched
UPS/generator pair? Alternatively, can they advise on matching of
the UPS to another supplier’s generator? Equally, they should be
able to discuss UPS sizing for the critical load. Although capacity,
battery autonomy and redundancy must be appropriate for the load’s
size and criticality, there is no benefit, and probably unnecessary
cost, in providing excess capacity – especially as modular systems
can be easily incremented later as needed.
The support strategy, like the hardware, should be realistically
matched to the user’s needs. Initial site surveys ensure the right
equipment is specified, while integration with related equipment and
site access and installation logistics are planned. A preventative
maintenance schedule ensures that batteries are kept in optimum
condition and potential problems are identified and repaired before
they cause failures. Remote monitoring and callout contracts can be
negotiated to match the criticality of the load.
Clues about a prospective UPS supplier’s actual rather than claimed
support capability and commitment can be gathered during early
negotiations. How timely, detailed and accurate are their written
and verbal responses? What is their product and project
documentation like? Are they happy to attend onsite project
meetings? Do they take health, safety, and environmental as well as
quality standards seriously? Are their technicians well trained, and
is their spares stock locally available? Are they willing and able
to offer recent industry references?
Finding the supplier that combines the most efficient and reliable
products and most comprehensive support strategy into the best power
protection package for a given load isn’t easy, but it’s the
approach that pays best dividends in terms of protection peace of
mind and ultimately lower cost of ownership.
