“Black Start” Capability is Critical to a Resilient Electric Grid

By Steven T. Naumann, former Vice President, Transmission and NERC Policy, Exelon

If a full-scale blackout occurs in one of the three electrical interconnections in the United States or, even worse, throughout the entire continental U.S., the only way to restore electricity is through a process known as “blackstart.”

All utilities have had blackstart plans for decades.  However, these plans were based on conventional threats – generally operational and equipment failures, possibly coupled with severe weather.  Today, these plans may be inadequate to restore electric service rapidly in the face of imminent emerging threats, especially a large-scale cybersecurity attack.

What is needed is (1) development of a Design Basis Threat (DBT) to understand the current and future threat environment; and (2) engineering analyses of the needs to rapidly recover, considering the challenge of the interdependencies between the electric grid and other critical infrastructure sections.  The Department of Energy should expeditiously develop a DBT and perform the required studies to guide changes in utility industry blackstart plans and provide a roadmap for investments to be able to successfully blackstart the electric system in the face of today’s new and evolving threats.

Recent cyberattacks have, again, shown the need for a resilient electric system.  While there is no accepted definition of resilience, the National Infrastructure Advisory Council (NIAC) developed a working definition a decade ago:

Infrastructure resilience is the ability to reduce the magnitude and/or duration of disruptive events. The effectiveness of a resilient infrastructure or enterprise depends upon its ability to anticipate, absorb, adapt to, and/or rapidly recover from a potentially disruptive event.[1]

More recently,  the Federal Energy Regulatory Commission (FERC) proposed a definition of resilience specific to the grid and FERC’s grid oversight role:

The ability to withstand and reduce the magnitude and/or duration of disruptive events, which includes the capability to anticipate, absorb, adapt to, and/or rapidly recover from such an event. [2]

Both these definitions include the need to “rapidly recover” from a disruptive event.[3]  This need was starkly illustrated in February 2021 during the extreme cold weather that affected the Electric Reliability Council Of Texas (ERCOT).  According to the CEO of ERCOT, if a full blackout had occurred, “power could have been out for 90% of Texans for weeks.”[4]  This “near miss” of a total blackout serves as a loud wakeup call for Texas, and the rest of the nation, to study and invest in grid infrastructure to ensure electric system operators have the ability to recover quickly if the worst happens.

Like all regions of the United States and Canada, Texas was supposed to have a significant, reliable “black start” capability built into its system. The North American Electric Reliability Corporation (NERC) requires utility owners and operators to have a restoration plan to restore electric service after a blackout.  These plans rely on blackstart resources,[5] such as small diesel, gas-turbines or hydroelectric plants, which can be started without relying on external power sources.  However, these small generators do not have the capability to restore even limited portions of the electric system – their job is to provide electricity to start larger generators.  Only then can system operators start restoring customer load.

Once these small blackstart generators are started, they are connected to transmission to provide electric circuits (called a “cranking path”)[6] in order to provide electricity to start larger generators (informally referred to as “next start generating units”).[7]  Once these larger generators are started, system operators connect load.  After that, more of the transmission system is connected, more generators are started, more load is connected, until the electric system is restored completely.  The entire restoration process is very complicated and varies under different situations.  Most blackstart plans contemplate parallel restoration by system operators in different areas.  At some point, these multiple restored islands need to be tied together.  This can be very complex and will be the subject for a future blog.[8]  However, the best blackstart plan will not work if the blackstart resources are not able to start or the “next start generators” are unavailable.

Although the joint NERC and FERC report and analysis of the Texas outage is not expected until later this year,[9] public reports have stated that a number of the generators that were needed to black start the electric system were out of service or did not have fuel available.[10]  As a number of former commissioners from the Public Utility Commission of Texas (PUCT) wrote in a report:

But in the February outages, it is not clear that all of ERCOT’s designated black-start assets would have been available to restart our grid due to maintenance, frozen equipment, or lack of fuel. If ERCOT had actually lost the entire power system to a full blackout, these black-start units would not have been able to do the job we pay them to do.  This is unacceptable.[11]

The ERCOT lessons strongly suggest it is time to review black start needs throughout the US.  While ERCOT operators prevented a full-scale blackout, this “near miss” of a major electrical interconnection warrants promptly starting a review of black start needs looking at multiple scenarios, including outages of interdependent infrastructure such as oil, natural gas, and telecommunications, as well as restarting the electric grid while a cyber and/or physical attack is ongoing.[12]

The need to study the issue before investing is important: new investments in black start capability will need to be paid for by ratepayers, and the impact of those costs cannot be ignored.  In the end, FERC and state regulatory commissions are charged with ensuring the rates are just and reasonable.  Therefore, it is essential that before investments are made, analyses of a full range of scenarios be conducted, including what may appear to be extreme scenarios, in order for policymakers and regulators to understand the basis for investments.

Looking more broadly, the risk of power outages based on the interdependencies between natural gas and electric infrastructure is not new, but would also benefit from detailed analysis.  The severe impact on power generation that could come from a loss of natural gas supplies has been raised within the past few years.[13]  It is important to understand that  extreme scenarios can occur more often than we think.[14] What are presently perceived as “fictional events” can later become very real.[15]  Thus the need to perform studies to understand possible ranges of outcomes, even those that may seem extreme.

The Department of Energy, working with the electric utility industry, other government agencies such as DOD and DHS, and state regulatory agencies,[16] should develop the DBT mentioned earlier and use it to perform analyses of black start requirements.[17]  This is consistent with a 2018 recommendation from the National Infrastructure Advisory Council to develop a federal design basis and design criteria to recover from a catastrophic power outage.[18]

DOE, possibly using the expertise of the National Laboratories, should perform scenario analyses using the DBT, and make recommendations for black start requirements based on the results of those scenarios.  Those recommendations can guide DOE and the industry in developing black start plans based on a current DBT.  Those plans, in turn, establish the basis for investments to help avoid an ERCOT-type scenario in the future.

As Congress debates a comprehensive infrastructure bill, it should provide funding for DOE to perform the necessary studies to ensure that the lessons of ERCOT and Texas are acted upon expeditiously and all regions will be prepared in the face of new and emerging threats.


[1] National Infrastructure Advisory Council, “Critical Infrastructure Resilience, Final Report and Recommendations,” at p. 8 (Sept. 8, 2009)

[2] Grid Reliability and Resilience Pricing, 162 FERC ¶ 61,012 at p. 23 (2018).

[3] The NERC Resilience Framework supplements the NIAC definition to include that rapid recovery be performed in a “coordinated and controlled manner and taking into consideration the extent of the damage.”  “Reliability Issues Steering Committee, Report on Resilience,” at p. 7 (Nov. 8, 2018)

[4] Statement by Bill Magness, President and Chief Executive Officer, ERCOT to Oversight and Investigations Subcommittee of the House Energy and Commerce Committee, at p.2 (March 24, 2021

[5] EOP-005-3, “System Restoration from Blackstart Resources” (Feb. 9, 2017)

[6] NERC defines a “cranking path” as “A portion of the electric system that can be isolated and then energized to deliver electric power from a generation source to enable the startup of one or more other generating units.”  SeeGlossary of Terms Used in NERC Reliability Standards,” 9th unnumbered page (updated June 28, 2021)

[7] Jose R. Gracia, et. al, “Hydropower Plants as Black Start Resources, Glossary, pp. ix, Oak Ridge National Laboratory” (May 2019)

[8] For a detailed explanation of the blackstart restoration process see id. at Section 2.0, Black Start Process Fundamentals, pp. 2.1-2.17.

[9] See Joint Inquiry into 2021 Cold Weather Grid Operations (NERC MRC Presentation Package – Aug. 12, 2021) at p. 17.

[10] Rebecca Smith, “The Texas Grid Came Close to an Even Bigger Disaster During February Freeze, Many ‘black start’ units, which are used to jolt failed electricity systems, weren’t working,” Wall Street Journal  (May 27, 2021)

[11] Wood, et. al, Report | Never Again; How to Prevent Another Major Texas Electric Failure,” (June 3, 2021). This is not the first time a post-event analysis has found the ability of black start units to function following a severe weather event affecting ERCOT.  See FERC/NERC Staff Report on the 2011 Southwest Cold Weather Event” at p. 8 (Aug. 2011)(“nearly half of [ERCOT’s] black start units were either on scheduled outage at the time of the event or failed during the event itself jeopardizing the utility’s ability to promptly restore the system had an uncontrolled ERCOT-wide blackout occurred.”

[12] It is important to analyze and learn from near-misses.  See Comments of The Honorable Cheryl LaFleur, Transcript of December 21, 2017 FERC Open Meeting, at 27:2-8 (“And one thing that has been observed and studied across many industries–not just electricity but in aviation, medicine, and other industries–is a well-established over decades statistical correlation between minor issues, or near-misses that are far more frequent, and then up at the top of the pyramid rare major events.”).

[13] See e.g., Prepared Direct Testimony of Dr. Paul Stockton on Behalf of Exelon Corporation, Docket No. RM18-1-000 at 9:14-13:10 (filed Oct. 23, 2017)(describing possible mutually reinforcing failures due to gas-electric interdependencies due to a “black sky” event); Pre-Technical Conference Comments of Steven T. Naumann on Behalf of Exelon Corporation, Docket No. AD18-11-000 at 6-8 (July 31, 2018); Id. at n.16 (“If no gas is available for generation at all due to residential use priority, electric blackouts could be extensive, potentially precluding even ‘rolling blackout’ alternatives”).

[14] For example, absent other factors, there only is a 41% probability that a once in ten-year event will occur within five years.  SeeImplementation of ERO Policies, Procedures, and Programs for 2021/2022 Winter Energy Readiness,” at 3 (July 4, 2021)(“Extreme does not mean rare”)

[15] Compare the 2011 movie Contagion with the Covid-19 Pandemic; Tom Clancy, “Debt of Honor” (1964) with September 11, 2001.  The 1989 movie Back to the Future Part II predicted that the long-suffering Chicago Cubs would win the 2015 World Series – it was off by only one year; the Cubs won in 2016.

[16] DOE should perform this work rather than NERC or FERC.  While NERC later may decide of modify its reliability standard, EOP-005-3 relating to blackstart (which FERC would approve), a review of blackstart needs should take a fresh look and eliminate any lingering compliance concerns.

[17] DOE should look at “all hazards” as part of its analysis for blackstart requirements.  Whether blackstart is needed due to cyber attacks, physical attacks, severe weather, a geomagnetic disturbance or an EMP attack, blackstart will be needed to recover.

[18] National Infrastructure Advisory Council, “Surviving a Catastrophic Power Outage, How to Strengthen the Capabilities of a Nation, Recommendation 2, pp. 9-10 (Dec. 2018).

Steve Naumann

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