POWER May 2020 - 52

COMMENTARY
Rethinking Redundancy
Design Guidelines in the
Power Industry
Kris Hahn
he power industry is undergoing massive transformational
change with the emergence of renewables, battery
storage, smart grids, Internet of Things, Industry
4.0, and more. Perhaps the timing is right to reconsider the
industry's approach to redundant systems. The best way to
do this is to look outside the power sector and apply lessons
from other industries.
T
How the Airline and Auto Industries Improved
Reliability
The airline industry is often regarded as a leader in reliability
thinking because of its early adoption of reliability-centered
maintenance (RCM). At one time, flying across the Atlantic
Ocean required airplanes with at least four engines. However,
as jet engines improved, it became the norm in the mid-1980s
to make trans-Atlantic flights with only two engines.
The airline industry focused on increasing the reliability of
the primary functions instead of counting on backup systems.
The savings in weight, fuel consumption, and maintenance
cost led to enormous savings for airline companies.
Another example is the spare tire in automobiles. For many
years, cars carried a full-sized extra spare in case of a flat
tire. Over the years, some car designers began to question
the need for the full spare. A full-sized spare tire costs more,
weighs a lot, and takes up valuable space.
In time, some manufacturers began providing a " donut
spare. " The intention was to replace the original tire's functionality,
but only for a short period of time (with reduced speeds)
until the main tire could be repaired or replaced. Other companies
tried including " Fix-a-Flat, " an aerosol can that contains
a sealant and enough air to re-inflate a tire, as a solution. Now,
some car companies have totally gotten rid of the spare tire
by increasing the reliability of the primary tire with " run-flat "
technology, which allows drivers to continue driving 50 miles
on a flat tire at reduced speeds.
The reliability of the primary functions has been increased
to levels where people are comfortable tolerating the risk
associated with driving without additional redundancy. They
have also done this by redefining the consequences of having
a flat tire to one where they just need to provide a means of
driving 50 miles to get home or to a car repair shop.
Applying Lessons to the Power Industry
The problem with an overreliance on redundancy is it requires
additional capital, maintenance, and repair over the life of the asset.
Yet, redundancy does not always lead to success due to poor
maintenance programs, testing that degrades performance, or
cannibalizing redundant systems for hard to locate spares.
When a primary component has a reliability of 0.9, little
52
is gained with additional redundancy beyond two parallel
components. Furthermore, when component reliability is low
(less than 0.7), multiple parallel components must be used
to raise the overall system reliability to 0.9 or greater. As discussed
above, these additional parallel components must be
maintained to impact the system reliability. To improve reliability,
it is more effective to focus technology, maintenance, and
capital on the primary function, instead of adding redundancy
with a low-reliability component.
Power utilities must adopt more modern thinking to work
with the communities they serve by managing risk and adopting
different service level expectations. New technologies
and approaches can be used to reduce the reliance on redundancies,
such as:
■ Combine sensor information, load history, work history, and
inspection results with artificial intelligence to intervene prior
to the onset of failure.
■ Use information about the performance of the grid with
smart grid technologies that anticipate failures.
■ Leverage storage technologies as redundant systems and
off-peak demand.
■ Use distributed energy resource assets on the grid.
■ Use a risk-based approach for grid modernization and grid
hardening, and focus on increasing the reliability of the primary
functions.
■ Work with federal, state, and local agencies to update regulations
for risk-based approaches to maintenance.
In effect, the power sector should use redundancy when
the risk of failure is intolerable, and the risk cannot be reduced
by other means. For existing systems with an excess
of redundancy with tolerable risks, redundancy can be used
to increase the capacity of systems with little additional capital
spending. New designs should justify redundancies based
on risk tolerance and look at other ways to reduce the risk
before using redundancy.
The airline industry has achieved huge savings by changing
its way of thinking, increasing reliability, and reducing risk.
Richard W. Taylor, a Boeing vice president and a former test
pilot, once said, " There have been 30 years of progress since
the current rules were written, you no longer have to have an
airport in the shadow of your wing tip every place you fly. "
If the airline industry can achieve this, every industry with
lesser consequences should be able to move in the same
direction with much less fear of catastrophic failures. Managing
the risk rather than avoiding the risk allows for leaner
designs, saving money and valuable resources. ■
-Kris Hahn is technology manager with Aladon, a global
provider of reliability-centered maintenance solutions.
www.powermag.com
POWER | May 2020
http://www.powermag.com
POWER May 2020

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