the electric grid
Invest in Black Start Generation
Reliability and Resilience in the Balance-Article 1
The twin impacts of Winter Storms Uri and Viola on Texas and its energy system was catastrophic. The problems contributing to the far-reaching consequences of this event are complex. However, there are key recurring themes that link these problems together that must be addressed if we expect to avoid a repeat of February 2021. Over the next several months, we will be revisiting this topic to highlight different aspects of the findings and recommendations from the Texas Chapter of the American Society of Civil Engineer’s (ASCE) Beyond Storms Committee’s Reliability and Resilience in the Balance report.
An electric grid is a complex network. It must continually be in balance with generation matching demand while maintaining transmission safety margins on a real-time basis. Frequency and voltage are the two main operating parameters of the power grid that must be maintained within certain limits to avoid damage to the grid, power generators, and to customers’ equipment, like motors. Frequency variations in power systems occur because of an imbalance between supply (generation) and demand (load).
To supply the grid, the system relies on two types of electricity generators. Dispatchable generators are controlled in their output and can be turned on and off based upon demand and the needs of the system, including ramping up and down production output to meet those needs. Non-dispatchable, or intermittent, generation produce energy only when its input source of energy is available (wind when the wind is blowing or solar when the sun is shining) instead of when the system or market needs generation. Complexities are created from managing the constantly changing output of dispatchable and intermittent generation against a constantly changing market demand. It is a complex system and in any complex system, conditions change, parts are stressed, and equipment breaks. The transmission system’s ability to transfer power may become limited due to thermal limits, voltage limits and dynamic stability limits at any given point in time. Weather and usage impact the system. A complex system such as ERCOT requires both reliable generation and a network that is resilient that can quickly recover from events of stress.
What Causes the Grid to Fail and Force Rolling Blackouts and What are Black Start Conditions?
During a severe overload caused by tripping or failure of generators or transmission lines, the grid system frequency will decline, due to an imbalance between load and supply or generation. If frequency declines too far, it will start to damage critical equipment and the fallback is to shut down the system to protect equipment and avoid severe damage. Deviations from these operating limits must be restored quickly before system components become damaged. Rolling blackouts are controlled and occur when parts of the grid are temporarily shut down and then the blacked-out portion of the grid is periodically rotated or “rolled over” to another geographic area while` service is restored to the original area as the grid is stabilized. Rolling blackouts are implemented to try and avoid the more severe complete blackout. Black start conditions are created when the entire grid goes down and these conditions are not controlled.
Restarting the Grid
The concept of restarting the grid appears simple, but the reality is far more complex. Many safety and control systems will have been compromised in the shutdown. Each of these must be inspected and isolated. Generators have a great deal of rotating equipment, pumps, safety, and control systems that must be orderly started up when returning the generator to service. In normal operations, the power plant relies on power supplied by the grid to start-up this equipment. Under black start conditions this is not an option. Large power plants must rely on black start generators, acting like defibrillators for this emergency energy source. These black start generators are the ultimate backstop to the system and must be well maintained, highly reliable and able to operate under a wide range of conditions supplied by dependable fuel. If you don’t regularly maintain a sprinkler system, you can’t rely on it to perform when you need it the most. Black Start generators must be reliably maintained to provide critical reliability and resilience to the network.
The Impact of Grid Failure
The loss of the entire grid is not something we ever want to experience. Imagine a situation where in a single moment everyone simultaneously loses access to clean water, sewage, refrigeration for food, food itself, fuel for vehicles, medical services, lights, security systems, internet, and phone service. All of it gone. Pat Wood, the former chairman of the PUCT described these conditions as being “equivalent to going back to the stone age” in nature.[i] Texas was less than 4 1/2 minutes from black start conditions on Monday morning February 15, 2021. The most critical generation failed to operate reliably.
Winter Storm Uri and Viola Black Start Generator Experience
There are 13 primary black start generators (back-up generators – the primary fail-safe to the system) and 15 secondary generators (think of them as the equivalent of back-up generators to the back-up generators) for a grand total of 28 generating black start units. According to the Black Start Working Group Presentation to the Reliability and Operations Subcommittee on June 3, 2021: 9 of the 13 primary black start generators experienced an outage during Uri and Viola or had forced outage or fuel problems and tripped offline and 12 of the 15 secondary generators had forced outage events during the EEA. This means that a total 21 of 28 (75%) black start generators had operational issues during the winter event. 7 of 32 outage causes were related to lack of fuel (the report does not provide the reason of the shortfall – supply, transport or contractual).
18 of these 28 units have only a single fuel resource. The low utilization or capacity factors of black start generators make it uneconomic for these resources to procure 24/7 year-round firm transport for natural gas supply needed to ensure reliable and dependable fuel supply. Dual fuel generators with secure on-site fuel storage of at least 1 fuel source is required to ensure reliable and dependable service from these units.
Why did this Happen?
There is a legacy of chronic under-investment to maintain critical infrastructure across the US. The energy only market design of ERCOT failed to adequately compensate dispatchable generators for being reliable and resilient and making ongoing investments and commitments to ensure reliability and resilience. The result was a problem called revenue insufficiency. Revenue insufficiency resulting in underfunding of the reliability and availability of these vital and critical last line of defense resources is not acceptable.
Texas must provide consistent, reliable, and adequate funding of sufficient duration to satisfy revenue sufficiency for black start generators including the incremental capital and operating expenses to support the following reliability investments:
- Dual-fuel capability with a minimum dedicated on-site fuel storage of 14 days running at 24/7 with regular best in-class testing of this capability.
- Winterization, reliability, and performance investments consistent with top decile, best-in-class performance.
- Black start generation that is incapable of dual-fuel service or unable to meet minimum top decile reliability and resilience metrics should be replaced.
The Executive summary and full report of Reliability and Resilience in the Balance provides further details of the analysis, conclusions and recommended actions to implement to avoid repeating the experiences of February 2021.
[i] Mose Buchele, Matt Largey (2021) If the Texas Power Grid Had Gone down, it would need a black start! How Long would that take?” KUT Radio, Austin’s NPR station, August 5, 2021