ELASTIC CRITICAL INFRASTRUCTURE
By Paul Johnson, UK Data
Centre Segment Leader, ABB
www.new.abb.com
Adapt to demand by adopting power distribution
systems based on standard modules to deliver
an elastic approach to critical infrastructure
On the one hand, data centre operators experience variable
demand on servers and therefore variable power load
and deployment. But on the other hand, they face fixed
costs from the fabric of data centre buildings and the grid
connections that feed them.
When surveyed, 64% of data centre experts identified
scalability as their number one issue as it sets them the
challenge of meeting growing demand at the same time
as maintaining uptime and operational efficiency. Having
power infrastructure that is flexible and scalable will help
them to better meet the needs of their servers – and
ultimately their customers.
Elastic critical infrastructure
The concept of Elastic Critical Infrastructure (ECI) has
developed to support this through the use of standard
products for medium voltage switchgear, UPS systems and
also low voltage switchgear. These are configured in a smart
way so that data centre operators can use it to power a pay
as you grow approach.
The concept enables data centre operators to use many
small design blocks to build a large-scale system over time to
meet the evolving needs of a growing data centre. The key is
to use standard products that are readily available on short
lead times, and that can be deployed at scale. Smart control
and communication capabilities help manage these systems
and leverage operational efficiency gains.
Improving asset utilisation
In a basic 2N system architecture operators use two
parallel systems, each of which is capable of meeting the
data centre’s entire load. The benefit is the certainty that
the infrastructure will supply loads. However, it comes with
the drawback that operators can never achieve more than
50% utilisation from infrastructure.
By using the ECI approach with many small modules,
operators no longer need to rely on one of two systems
operating. The approach is perhaps most valuable for UPS
systems, which are relatively costly per kW delivered in
comparison with medium and low voltage switchgear and
transformers. For example, with four 500 kW UPS modules
to support a 1.5 MW IT load, a malfunction of one module
won’t affect overall power availability and the remaining
three modules can be used as a group to meet the entire
power demand.
By building in smaller design blocks, operators are able
to deploy various architectures, even changing between
architectures as the facility is fitted out. Depending on
the size of the block that’s used, a facility could start out
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with two 1MW power streams in a 2N architecture, and
as the facility increases in capacity, an additional power
stream could be included to reconfigure the system to be a
distributed redundant – three to make two architecture.
In general, the flexibility of a system grows as an
operator installs more modules, offering more options to
create load groups. In addition, the impact of any single
module reduces – with the important implication that
operators can downsize overall capacity and increase the
utilisation factor (UF) of each module and of the system as
a whole.
Reduce stranded capacity in UPS
Traditional monolithic UPS systems contain multiple UPS
modules and shared components such as switchgear. This
provides a straightforward approach but has the drawback
that capacity can become stranded as the UPS module
ratings are sometimes quite large. In addition, a failure on
any single UPS module can impact the availability of the
UPS system as a whole.
With the ECI approach, modular UPS systems are
employed and include multiple power modules. For
example, some modular UPS systems have their own
dedicated control logic, static bypass, user interface and
switchgear that enables each power module to act as a
complete UPS. The result is greater levels of flexibility
to group power modules to feed loads and less stranded
capacity and higher availability of backup power.
How ECI influences transformers & circuit breakers
The laws of physics mean that a fault on a large single
transformer can give rise to high fault levels. As an
alternative, using multiple smaller transformers will meet
the same capacity but with a significantly reduced fault
level. In turn, operators can downsize their protective
devices (ACBs and MCCBs), with the potential to find
significant cost savings and also provide a safer system
because the lower fault levels mean reduced incident
energy in case of an arc flash event.
Communication and control for ECI
Switching to the ECI approach offers huge opportunities for
capital savings. However, the smaller blocks do have more
components so implementing digital metering of current
and voltage, as well as monitoring of temperature and
component wear, will provide accurate and timely data for
data centre infrastructure management (DCIM) systems.
This will optimise operations by making decisions based on
availability, status and condition of critical power. n
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