Rethinking Redundancy Design Guidelines in the Power Industry

The 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.

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 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.

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