In December 2023, the North American Electric Reliability Corporation (NERC) presented a study titled “Blackstart and Next-Start Resource Availability in the Texas Interconnection” to the Federal Energy Regulatory Commission (FERC). This study was a response to the FERC-NERC-Regional Entity Staff Report released in February 2021, which addressed the cold weather outages in Texas and South-Central US. Initiated in November 2022, the study aimed to evaluate the accessibility of critical blackstart resources (essential for restarting the electric power grid after a complete shutdown, particularly during extreme weather conditions) and next-start resources within the Electric Reliability Council of Texas’ (ERCOT) [Texas region independent system operator (ISO)] procurement process for its system restoration plan.

Black start is a generating unit and its associated set of equipment that can be started without support from the connected electric transmission system or is designed to remain energised without connection to the remainder of the system. A next-start generating unit is the first generating unit in the cranking path to be energised using power from the black start generating unit. A cranking path is the portion of the electric transmission system that can be isolated and then energised to deliver electric power from a generation source to enable the startup of one or more other generating units.

The joint study team makes several key findings on:

  • Black start system restoration plans
  • Fuel supply contracts and delivery infrastructure for black start and next-start generating resources
  • Expanded testing and fuel-switching capabilities
  • Black start and system restoration operating personnel training practices, and procedures

Under the joint study, the ISO has defined procurement processes and procedures in place to secure black start resources, and has verified, through simulations and models, the sufficiency of the black start resources in its black start system restoration plan. However, the fuel mix of the black start resources available to the ISO has limited fuel diversity and the ISO relies heavily on natural gas as fuel for its black start and next-start resources.

Regarding training, the joint study team found that participants who perform additional testing of black start resources and restoration training use the knowledge gained from these activities to modify, update, and improve their black start system restoration plans. It observed that the electric and natural gas industries are heavily reliant on one another to maintain reliable operations. For this reason, the joint study team concluded that having open lines of communication in place between the two industries in preparation for a black start system restoration scenario is necessary to facilitate the timely restoration of the electric grid.

From these findings, the team identified best practices and opportunities for improvement in the participants’ programmes/procedures and developed associated recommendations. These recommendations apply to both the electric and natural gas industries regarding practices, procedures, and methodologies aimed at improving black start system restoration overall and black start capability planning and testing.

The study recognises that there is a need for a better understanding of the actions required to address a black start system restoration scenario and which electric and natural gas entities would need to take action in such a scenario. To that end, the study highlights the need for the electric and natural gas industries to work together to develop a joint black start system restoration plan that considers extreme cold weather conditions and the mutual interdependence of these two complex and important industries.

Other recommendations include approaches to improve electric and natural gas industry coordination and communication, mitigate the risks to the operability of black start resources, test black start resources, assess the validity of black start system restoration plans, incorporate a variety of options into black start system restoration plans, and the use of natural gas storage.

Recommendations

As mentioned earlier, black start restoration requires the electric and natural gas entities to work collaboratively across multiple jurisdictions and functional responsibilities, including but not limited to, transmission operators, generator operators, distribution providers, reliability coordinators, and natural gas producers, processors, and transporters. The joint study team makes the below recommendations to these entities as a whole, understanding that some entities may have a larger role than others in the development and implementation of a black start restoration plan.

1. Entities responsible for developing and implementing a black start system restoration plan should:

a) Examine the diversity of fuel, single points of failure, fuel arrangements, and other limitations of each black start resource. Fully understanding the types of fuel arrangements would provide entities an insight into the likelihood of the black start resource being available during an emergency or black start system restoration scenario. Assessing the additional limitations of black start resources would help entities prepare for, mitigate, and respond to black start system restoration scenarios.
b) Evaluate and incorporate, where feasible, a wide variety of options into their black start system restoration plans. For example, entities should consider the use of electrical bypasses, high voltage direct current (HVDC) ties, variable frequency transformers, block load transfers, and non-fuel energy resources (for example , inverter-based resources (IBRs) and batteries). During a black start system restoration scenario, these alternatives could provide entities with other options beyond a reliance on traditional black start resources. Having these options available during a black start system restoration scenario would add diversity and resilience, particularly if natural gas to black start and next-start resources are limited or unavailable. While the preceding list encompasses examples that entities could use, it is not exclusive, and entities should perform their study of alternatives.
c) Incorporate off-site natural gas storage in black start system restoration plans. Doing so could provide entities with more fuel supply options during black start system restoration. The natural gas supply chain may be severely stressed or completely unavailable during a black start system restoration scenario. Stored natural gas may increase the likelihood of black start and next-start resources being able to secure fuel more quickly and reliably in the event of a blackout, which may be necessary to start system restoration.
d) Implement a testing requirement for black start resources to perform alternate fuel startup tests completely on alternate fuel. Performing these alternate fuel startup tests would confirm that dual-fuel capable black start resources can start on alternate fuel during a blackout when no other external electricity sources are available and primary fuel is unavailable. Additionally, these requirements should be clearly defined so that the black start resources can perform these tests effectively.

2) The appropriate state and other authorities with jurisdiction should facilitate and moderate engagement among the entities responsible for developing and implementing a black start system restoration plan, including but not limited to, electric generation owners and operators, electric transmission owners and operators, electric distribution owners and operators, and natural gas supply chain owners and operators to:

a) Assess the impact of a blackout on the natural gas supply chain with a focus on fuel availability to black start and next-start resources. This assessment could help the electric and natural gas industries better understand what is required in a black start system restoration scenario and which electric and natural gas entities are responsible for black start system restoration. This assessment should include the impact on the natural gas supply chain and evaluate the impact on the fuel availability to black start and next-start resources. Fuel availability will impact their performance and restoration capabilities during a black start system restoration scenario. Furthermore, this assessment should determine the resilience of the electrical system based on the risk of the natural gas system not being available. In addition, such an assessment could determine the impact on the natural gas system in the event of a blackout, particularly during an extreme cold weather event. In Texas, this assessment should expand upon the critical infrastructure mapping that was developed by the Public Utility Commission of Texas (PUCT) and Railroad Commission (RRC), which regulates the natural gas industry, after Winter Storm Uri. Results of the assessment could aid in further collaboration between the electric and natural gas industries, and drive potential changes to the black start procurement process, including which units are selected to be black start resources and their fuel procurement requirements.
b) Develop a coordinated black start system restoration plan that incorporates the needs of both industries. The electric and natural gas entities necessary for restoration should work collaboratively to develop the restoration plan. In Texas, this coordinated black start system restoration plan should further distinguish the critical load designations developed by PUCT and RRC after Winter Storm Uri to account for the loads critical for restoration. The plan should prioritise the natural gas infrastructure required to supply fuel to the black start, next-start, and other essential resources necessary for restoration within each restoration island. Additionally, this plan should prioritise the sequence and timing for energising critical electrical substations and natural gas infrastructure to ensure a more synchronized black start system restoration.

3. The appropriate state and other authorities with jurisdiction over developing and defining natural gas curtailment plans and standards should evaluate elevating the priority of natural gas supply and transportation to black start and next-start resources. The fuel supply curtailment to these resources could lead to their unavailability. The joint study team finds that this evaluation would help entities ensure that fuel supplies are prioritised and thus, available to black start and next-start resources when fuel supplies are limited.

Observed practices for consideration

The joint study team observed that the participants have many practices and procedures on black start resource availability, testing, communication and coordination, and training, that serve to enhance their preparations for black start system restoration. While they may not be universally applicable, incorporating these observed practices where appropriate could add significant value and resilience to the electric grid. Examples of these beneficial practices observed by the joint study team include:

  • Installing permanent winterisation measures, where possible, to minimise the use of temporary measures, such as portable space heaters, at generating resources. Permanent mitigation could limit the amount of annual maintenance required.
  • Periodically reviewing and identifying generating resources capable of operating in isochronous mode (where a generator’s output is controlled to maintain a constant frequency, rather than voltage) when developing restoration plans. This information is critical in identifying the generating resources capable of controlling frequency within islands during restoration.
  • Performing expanded testing, where feasible, to confirm the viability of black start capability through coordination between black start resources and transmission entities. Expanded testing could be used to confirm the viability of black start system restoration plans as well as to update system models and black start system restoration training programs.

The joint study team views the recommendations in this report as proactive, to help the entities responsible for black start system restoration to pre-emptively plan for recovery from a blackout. While the recommendations in this report are voluntary and imposes no obligations beyond those required by the relevant NERC reliability standards, the joint study team strongly urges that the report’s recommendations and observed practices be implemented by the entities necessary for black start system restoration.