What are grid reliability and grid resiliency?

Most of us understand grid reliability to be the ability of the power system to deliver electricity in the quantity and with the quality demanded by users. This is accomplished by having enough generation resources to meet all power demands and having enough built-in redundancy to minimize the effects of single point failures. To summarize, grid reliability means that the lights always turn on when the switch is thrown. This is the ultimate “end goal” of the electric grid.

But what about grid resiliency? Grid resiliency has become one of the buzz words of the past couple of years. Grid resiliency is concerned with the ability of a system to recover from adversity due to more widespread disruptive events. Resilience emphasizes the idea that disruptive events can and do occur and that systems should be designed to bounce back quicker and stronger. By designing systems to certain standards, grid resiliency reduces the impact from disruptive events to less than they could have been otherwise. Disruptive events may include natural disasters, cyber impacts and operational issues. Grid resiliency is becoming increasingly important as major storms become more frequent and the abilities of hackers to commit cyber-attacks continues to grow.

These two concepts are interrelated. To meet the end goal of “the lights coming on,” the electric grid must be resilient enough to bounce back from disruptive events quickly.

In September 2017, U.S. Secretary of Energy Rick Perry proposed that the Federal Energy Regulatory Commission (FERC) act to address threats to U.S. electric grid resiliency. The Secretary urged FERC to issue a final rule to implement reforms that would fully price the generation resources necessary to maintain electric grid reliability and resiliency. Secretary Perry said:

“A reliable and resilient electrical grid is critical not only to our national and economic security, but also to the everyday lives of American families. A diverse mix of power generation resources, including those with on-site reserves, is essential to the reliable delivery of electricity—particularly in times of supply stress such as recent natural disasters. My proposal will strengthen American energy security by ensuring adequate reserve resource supply and I look forward to the Commission acting swiftly on it.”

However, FERC rejected the proposed rule-making. FERC did, however, proceed to examine the question: What exactly is “resilience,” and do we need it? FERC directed regional transition organizations (RTOs) and independent system operators (ISOs) to supply information on “certain resilience issues and concerns” to see if additional steps were needed to affirm the resilience of the grid.

The comments from the RTOs and ISOs tended to define grid resiliency as another, expanded, meaning of grid reliability. Their comments to FERC were that “all is well with each of our respective systems.” However, historical evidence shows that we, as an industry, do not have a clear view of what resilience is, how to measure it, or how to ensure it.

So where does that leave us? It is pretty clear that the electric grid is reliable. However, there is an increasing threat to the grid’s resilience and the future of American energy security, particularly due to the changing nature of cyber incidents. It may be time for the Transmission & Distribution industry to finally follow Secretary Perry’s proposal to act to address threats to U.S. electric grid resiliency.

Grid reliability is a critical measure as it is important to provide power consistently with as few disruptions as possible. While this is and should always remain the ultimate goal of the electric grid, grid resiliency can and should be a necessary component of grid reliability.