Just one day before Category 4 Hurricane Harvey hit the Texas coast causing power outages for 300,000 customers, the DOE released its long-awaited grid study entitled “Staff Report to the Secretary on Electricity Markets and Reliability." The study included an eerily predictive recommendation about the need for greater emphasis on grid resilience.
DOE officials noted in their 187-page report to the Secretary of Energy that grid operators have been assessing reliability concerns for some time as the percentage of renewable energy resources on the grid increased. That focus, and potentially the care grid operators have taken, has paid off because even as baseload plants retired and alternative energy resources increased, DOE found that grid operators have, to date, maintained a reliable grid. However, in light of recent major storms like Hurricane Sandy and studies conducted to simulate extreme weather events like the polar vortex experienced during the winter of 2014 in the Northeast, DOE’s grid study stressed the need to focus on resiliency as well as reliability.
We have spent years highly focused on reliability in the utility industry. There are numerous measurements like SAIFI, SAIDI, CAIDI and others used to track the industry’s progress toward greater reliability. It seems like Hurricane Sandy was a turning point, at least in the Northeast, for utilities also to train their sights on resilience. For utilities in other parts of the country that are routinely hit by severe storms and flooding, the conversion to a dual focus of reliability and resiliency happened years earlier.
Despite the progress many companies have made on resiliency, in light of Harvey and now Irma, DOE’s recommendations regarding a greater focus on resiliency appear more important than ever. A large portion of past work by DOE and the rules and regulations from NERC and FERC focus on reliability. Studies of grid reliability focus on everything from generator technology, fuel availability and diversity to establishing the correct level of reserves (frequency, spinning, non-spinning, operating, regulation, replacement, etc.) and appropriate transmission investment. The work related to resiliency appears to be much less charted.
DOE states that NERC uses the following definition for infrastructure resiliency: the ability to reduce the magnitude and/or duration of disruptive events. While we think primarily of severe weather events in the context of resiliency, planners and regulators also include extended physical and cyber attacks as well as geomagnetic disturbances as potentially disruptive events.
We analyze reliability using well defined and measured criteria such as the time scales shown in the below graphic from DOE’s report to the Secretary.
Resiliency, on the other hand, has not been universally defined and measured in detail with respect to the bulk power system. We know from studies performed by PJM to analyze resource mix and fuel diversity issues that system configurations that improve reliability may not benefit resiliency. For example, PJM studies showed that scenarios with a heavy reliance on one resource type may result in adequate reliability, but be less resilient than a portfolio with greater diversity.
That sounds logical, but PJM also found that more diverse portfolios are not necessarily more reliable. Instead, there are resource blends between the most diverse and least diverse portfolios that provide better reliability attributes. In light of such potentially incongruent results when planning for reliability vs. resilience, PJM recognized the need for further investigation regarding system resiliency planning. The grid operator has since drafted a “Resilience Roadmap” and is planning workshops to collect input on this topic.
The DOE appropriately recognized the need for more research to define, quantify and value resilience going forward. T&D World magazine has published numerous articles since 2012 describing measures utilities have taken to harden their electric systems on a case-by-case basis in response to damage inflicted by major storms. Yet, our industry does not have universal planning and operating criteria for system resilience or defined standards to mitigate system damage, reduce customer outage times and otherwise speed emergency event recovery. As our system evolves with changes in generator types, fuel mix, increasing renewables and alternative energy resources, is it time to systematically plan for resilience as well as reliability? The symposiums being held by PJM, work underway at Sandia National Laboratories and DOE’s own Grid Modernization Initiative (GMI) should help determine the most prudent path forward.