Despite the recent retirement of “blackstart” units, grid operators have sufficient resources to quickly restore systems in the event of widespread outages, suggests a new report by staff at the Federal Energy Regulatory Commission (FERC) and the North American Electric Reliability Corporation (NERC).
The report—“FERC-NERC-Regional Entity Joint Review of Restoration and Recovery Plans”—released May 2 presents findings from a joint FERC and NERC study that evaluated blackstart resources and planning by nine utilities registered with NERC. NERC—a non-profit international regulatory authority tasked with assuring reliability and security of the grid—defines a blackstart resource as one or more generating units and associated equipment that can be started without support from the bulk power system and is designed to remain energized without connection to the system. A blackstart unit energizes other equipment. The first generating unit in its cranking path is known as a “next-start” generating unit.
According to the report, blackstart generating units included in the participants’ system restoration strategies—and most participants had more than one, it noted—ranged from small (50 MVA) to larger units (100–200 MVA), to banks of generating units exceeding 1,000 MVA in capacity. Resources include a mix of coal and gas-fired steam units, gas combustion units, and hydroelectric units. While none of the participants used wind or solar for blackstart services, some were in discussion with vendors to assess battery storage systems, it said.
Some utilities and grid entities surveyed in the study noted that the total number of available blackstart-capable units have decreased over the past decade, owing to the impact of environmental rules, and the retirement of non-economic and aging assets.
Participants responding to the loss of individual blackstart units generally developed mechanisms to identify alternatives, sometimes re-identifying priority loads or re-engineering system restoration plants to include additional flexibility and redundancy.
“Other participants have seen little turnover in their fleet of blackstart resources, but have experienced changes in their next-start generating units and automatic load rejection generating units due to similar factors,” the report notes. “Nevertheless, all participants have verified that they have sufficient blackstart resources to support their current restoration plans. In addition, most participants indicated that they have access to other blackstart-capable units beyond those specifically identified in their current restoration plans.”
Some utilities have also expanded testing of blackstart capability, including testing energization of the next-start generating units. “These utilities have gained valuable knowledge used to modify, update and improve their system restoration plans,” NERC said in a statement on May 2. “The utilities also used the knowledge gained to update and improve their existing steady state and dynamic models supporting their system restoration plans, as well as their system restoration drills.”
In their report, NERC and FERC staff recommended, however, that industry voluntarily consider a number of practices, procedures, and methodologies to improve system restoration overall, and for blackstart capability planning and testing in particular.
For example, because the study concludes that reliance on a single-fuel blackstart resource without fuel storage capacity or a firm fuel arrangement could cause issues during a restoration event, it recommends that single fuel-dependent blackstart generators develop alternative fuel capabilities or coordinate with fuel providers to mitigate this risk.
The study also recommends that regional transmission organizations (RTOs) and independent system operators (ISOs) examine the adequacy of compensation for services and benefits provided by blackstart resources, “including any potential threat or impact on blackstart resource procurement and retention under current compensation mechanisms.” It also calls on the grid entities to examine compensation for “next-start” generating units used in system restoration, including compensation for costs associated with participating in blackstart-related services such as expanded testing.
Finally, grid entities should coordinate with blackstart and next-start generation operators to perform expanded testing of blackstart cranking paths, it says.
—Sonal Patel is a POWER associate editor (@sonalcpatel, @POWERmagazine)